Documentation/DocBook/v4l/controls.xml

   1   <section id="control">
   2     <title>User Controls</title>
   3
   4     <para>Devices typically have a number of user-settable controls
   5 such as brightness, saturation and so on, which would be presented to
   6 the user on a graphical user interface. But, different devices
   7 will have different controls available, and furthermore, the range of
   8 possible values, and the default value will vary from device to
   9 device. The control ioctls provide the information and a mechanism to
  10 create a nice user interface for these controls that will work
  11 correctly with any device.</para>
  12
  13     <para>All controls are accessed using an ID value. V4L2 defines
  14 several IDs for specific purposes. Drivers can also implement their
  15 own custom controls using <constant>V4L2_CID_PRIVATE_BASE</constant>
  16 and higher values. The pre-defined control IDs have the prefix
  17 <constant>V4L2_CID_</constant>, and are listed in <xref
  18 linkend="control-id" />. The ID is used when querying the attributes of
  19 a control, and when getting or setting the current value.</para>
  20
  21     <para>Generally applications should present controls to the user
  22 without assumptions about their purpose. Each control comes with a
  23 name string the user is supposed to understand. When the purpose is
  24 non-intuitive the driver writer should provide a user manual, a user
  25 interface plug-in or a driver specific panel application. Predefined
  26 IDs were introduced to change a few controls programmatically, for
  27 example to mute a device during a channel switch.</para>
  28
  29     <para>Drivers may enumerate different controls after switching
  30 the current video input or output, tuner or modulator, or audio input
  31 or output. Different in the sense of other bounds, another default and
  32 current value, step size or other menu items. A control with a certain
  33 <emphasis>custom</emphasis> ID can also change name and
  34 type.<footnote>
  35         <para>It will be more convenient for applications if drivers
  36 make use of the <constant>V4L2_CTRL_FLAG_DISABLED</constant> flag, but
  37 that was never required.</para>
  38       </footnote> Control values are stored globally, they do not
  39 change when switching except to stay within the reported bounds. They
  40 also do not change &eg; when the device is opened or closed, when the
  41 tuner radio frequency is changed or generally never without
  42 application request. Since V4L2 specifies no event mechanism, panel
  43 applications intended to cooperate with other panel applications (be
  44 they built into a larger application, as a TV viewer) may need to
  45 regularly poll control values to update their user
  46 interface.<footnote>
  47         <para>Applications could call an ioctl to request events.
  48 After another process called &VIDIOC-S-CTRL; or another ioctl changing
  49 shared properties the &func-select; function would indicate
  50 readability until any ioctl (querying the properties) is
  51 called.</para>
  52       </footnote></para>
  53
  54     <table pgwide="1" frame="none" id="control-id">
  55       <title>Control IDs</title>
  56       <tgroup cols="3">
  57         &cs-def;
  58         <thead>
  59           <row>
  60             <entry>ID</entry>
  61             <entry>Type</entry>
  62             <entry>Description</entry>
  63           </row>
  64         </thead>
  65         <tbody valign="top">
  66           <row>
  67             <entry><constant>V4L2_CID_BASE</constant></entry>
  68             <entry></entry>
  69             <entry>First predefined ID, equal to
  70 <constant>V4L2_CID_BRIGHTNESS</constant>.</entry>
  71           </row>
  72           <row>
  73             <entry><constant>V4L2_CID_USER_BASE</constant></entry>
  74             <entry></entry>
  75             <entry>Synonym of <constant>V4L2_CID_BASE</constant>.</entry>
  76           </row>
  77           <row>
  78             <entry><constant>V4L2_CID_BRIGHTNESS</constant></entry>
  79             <entry>integer</entry>
  80             <entry>Picture brightness, or more precisely, the black
  81 level.</entry>
  82           </row>
  83           <row>
  84             <entry><constant>V4L2_CID_CONTRAST</constant></entry>
  85             <entry>integer</entry>
  86             <entry>Picture contrast or luma gain.</entry>
  87           </row>
  88           <row>
  89             <entry><constant>V4L2_CID_SATURATION</constant></entry>
  90             <entry>integer</entry>
  91             <entry>Picture color saturation or chroma gain.</entry>
  92           </row>
  93           <row>
  94             <entry><constant>V4L2_CID_HUE</constant></entry>
  95             <entry>integer</entry>
  96             <entry>Hue or color balance.</entry>
  97           </row>
  98           <row>
  99             <entry><constant>V4L2_CID_AUDIO_VOLUME</constant></entry>
 100             <entry>integer</entry>
 101             <entry>Overall audio volume. Note some drivers also
 102 provide an OSS or ALSA mixer interface.</entry>
 103           </row>
 104           <row>
 105             <entry><constant>V4L2_CID_AUDIO_BALANCE</constant></entry>
 106             <entry>integer</entry>
 107             <entry>Audio stereo balance. Minimum corresponds to all
 108 the way left, maximum to right.</entry>
 109           </row>
 110           <row>
 111             <entry><constant>V4L2_CID_AUDIO_BASS</constant></entry>
 112             <entry>integer</entry>
 113             <entry>Audio bass adjustment.</entry>
 114           </row>
 115           <row>
 116             <entry><constant>V4L2_CID_AUDIO_TREBLE</constant></entry>
 117             <entry>integer</entry>
 118             <entry>Audio treble adjustment.</entry>
 119           </row>
 120           <row>
 121             <entry><constant>V4L2_CID_AUDIO_MUTE</constant></entry>
 122             <entry>boolean</entry>
 123             <entry>Mute audio, &ie; set the volume to zero, however
 124 without affecting <constant>V4L2_CID_AUDIO_VOLUME</constant>. Like
 125 ALSA drivers, V4L2 drivers must mute at load time to avoid excessive
 126 noise. Actually the entire device should be reset to a low power
 127 consumption state.</entry>
 128           </row>
 129           <row>
 130             <entry><constant>V4L2_CID_AUDIO_LOUDNESS</constant></entry>
 131             <entry>boolean</entry>
 132             <entry>Loudness mode (bass boost).</entry>
 133           </row>
 134           <row>
 135             <entry><constant>V4L2_CID_BLACK_LEVEL</constant></entry>
 136             <entry>integer</entry>
 137             <entry>Another name for brightness (not a synonym of
 138 <constant>V4L2_CID_BRIGHTNESS</constant>). This control is deprecated
 139 and should not be used in new drivers and applications.</entry>
 140           </row>
 141           <row>
 142             <entry><constant>V4L2_CID_AUTO_WHITE_BALANCE</constant></entry>
 143             <entry>boolean</entry>
 144             <entry>Automatic white balance (cameras).</entry>
 145           </row>
 146           <row>
 147             <entry><constant>V4L2_CID_DO_WHITE_BALANCE</constant></entry>
 148             <entry>button</entry>
 149             <entry>This is an action control. When set (the value is
 150 ignored), the device will do a white balance and then hold the current
 151 setting. Contrast this with the boolean
 152 <constant>V4L2_CID_AUTO_WHITE_BALANCE</constant>, which, when
 153 activated, keeps adjusting the white balance.</entry>
 154           </row>
 155           <row>
 156             <entry><constant>V4L2_CID_RED_BALANCE</constant></entry>
 157             <entry>integer</entry>
 158             <entry>Red chroma balance.</entry>
 159           </row>
 160           <row>
 161             <entry><constant>V4L2_CID_BLUE_BALANCE</constant></entry>
 162             <entry>integer</entry>
 163             <entry>Blue chroma balance.</entry>
 164           </row>
 165           <row>
 166             <entry><constant>V4L2_CID_GAMMA</constant></entry>
 167             <entry>integer</entry>
 168             <entry>Gamma adjust.</entry>
 169           </row>
 170           <row>
 171             <entry><constant>V4L2_CID_WHITENESS</constant></entry>
 172             <entry>integer</entry>
 173             <entry>Whiteness for grey-scale devices. This is a synonym
 174 for <constant>V4L2_CID_GAMMA</constant>. This control is deprecated
 175 and should not be used in new drivers and applications.</entry>
 176           </row>
 177           <row>
 178             <entry><constant>V4L2_CID_EXPOSURE</constant></entry>
 179             <entry>integer</entry>
 180             <entry>Exposure (cameras). [Unit?]</entry>
 181           </row>
 182           <row>
 183             <entry><constant>V4L2_CID_AUTOGAIN</constant></entry>
 184             <entry>boolean</entry>
 185             <entry>Automatic gain/exposure control.</entry>
 186           </row>
 187           <row>
 188             <entry><constant>V4L2_CID_GAIN</constant></entry>
 189             <entry>integer</entry>
 190             <entry>Gain control.</entry>
 191           </row>
 192           <row>
 193             <entry><constant>V4L2_CID_HFLIP</constant></entry>
 194             <entry>boolean</entry>
 195             <entry>Mirror the picture horizontally.</entry>
 196           </row>
 197           <row>
 198             <entry><constant>V4L2_CID_VFLIP</constant></entry>
 199             <entry>boolean</entry>
 200             <entry>Mirror the picture vertically.</entry>
 201           </row>
 202         <row>
 203           <entry><constant>V4L2_CID_HCENTER_DEPRECATED</constant> (formerly <constant>V4L2_CID_HCENTER</constant>)</entry>
 204             <entry>integer</entry>
 205             <entry>Horizontal image centering. This control is
 206 deprecated. New drivers and applications should use the <link
 207 linkend="camera-controls">Camera class controls</link>
 208 <constant>V4L2_CID_PAN_ABSOLUTE</constant>,
 209 <constant>V4L2_CID_PAN_RELATIVE</constant> and
 210 <constant>V4L2_CID_PAN_RESET</constant> instead.</entry>
 211           </row>
 212           <row>
 213             <entry><constant>V4L2_CID_VCENTER_DEPRECATED</constant>
 214             (formerly <constant>V4L2_CID_VCENTER</constant>)</entry>
 215             <entry>integer</entry>
 216             <entry>Vertical image centering. Centering is intended to
 217 <emphasis>physically</emphasis> adjust cameras. For image cropping see
 218 <xref linkend="crop" />, for clipping <xref linkend="overlay" />. This
 219 control is deprecated. New drivers and applications should use the
 220 <link linkend="camera-controls">Camera class controls</link>
 221 <constant>V4L2_CID_TILT_ABSOLUTE</constant>,
 222 <constant>V4L2_CID_TILT_RELATIVE</constant> and
 223 <constant>V4L2_CID_TILT_RESET</constant> instead.</entry>
 224           </row>
 225           <row id="v4l2-power-line-frequency">
 226             <entry><constant>V4L2_CID_POWER_LINE_FREQUENCY</constant></entry>
 227             <entry>enum</entry>
 228             <entry>Enables a power line frequency filter to avoid
 229 flicker. Possible values for <constant>enum v4l2_power_line_frequency</constant> are:
 230 <constant>V4L2_CID_POWER_LINE_FREQUENCY_DISABLED</constant> (0),
 231 <constant>V4L2_CID_POWER_LINE_FREQUENCY_50HZ</constant> (1) and
 232 <constant>V4L2_CID_POWER_LINE_FREQUENCY_60HZ</constant> (2).</entry>
 233           </row>
 234           <row>
 235             <entry><constant>V4L2_CID_HUE_AUTO</constant></entry>
 236             <entry>boolean</entry>
 237             <entry>Enables automatic hue control by the device. The
 238 effect of setting <constant>V4L2_CID_HUE</constant> while automatic
 239 hue control is enabled is undefined, drivers should ignore such
 240 request.</entry>
 241           </row>
 242           <row>
 243             <entry><constant>V4L2_CID_WHITE_BALANCE_TEMPERATURE</constant></entry>
 244             <entry>integer</entry>
 245             <entry>This control specifies the white balance settings
 246 as a color temperature in Kelvin. A driver should have a minimum of
 247 2800 (incandescent) to 6500 (daylight). For more information about
 248 color temperature see <ulink
 249 url="http://en.wikipedia.org/wiki/Color_temperature">Wikipedia</ulink>.</entry>
 250           </row>
 251           <row>
 252             <entry><constant>V4L2_CID_SHARPNESS</constant></entry>
 253             <entry>integer</entry>
 254             <entry>Adjusts the sharpness filters in a camera. The
 255 minimum value disables the filters, higher values give a sharper
 256 picture.</entry>
 257           </row>
 258           <row>
 259             <entry><constant>V4L2_CID_BACKLIGHT_COMPENSATION</constant></entry>
 260             <entry>integer</entry>
 261             <entry>Adjusts the backlight compensation in a camera. The
 262 minimum value disables backlight compensation.</entry>
 263           </row>
 264           <row>
 265             <entry><constant>V4L2_CID_CHROMA_AGC</constant></entry>
 266             <entry>boolean</entry>
 267             <entry>Chroma automatic gain control.</entry>
 268           </row>
 269           <row>
 270             <entry><constant>V4L2_CID_CHROMA_GAIN</constant></entry>
 271             <entry>integer</entry>
 272             <entry>Adjusts the Chroma gain control (for use when chroma AGC
 273             is disabled).</entry>
 274           </row>
 275           <row>
 276             <entry><constant>V4L2_CID_COLOR_KILLER</constant></entry>
 277             <entry>boolean</entry>
 278             <entry>Enable the color killer (&ie; force a black &amp; white image in case of a weak video signal).</entry>
 279           </row>
 280           <row id="v4l2-colorfx">
 281             <entry><constant>V4L2_CID_COLORFX</constant></entry>
 282             <entry>enum</entry>
 283             <entry>Selects a color effect. Possible values for
 284 <constant>enum v4l2_colorfx</constant> are:
 285 <constant>V4L2_COLORFX_NONE</constant> (0),
 286 <constant>V4L2_COLORFX_BW</constant> (1),
 287 <constant>V4L2_COLORFX_SEPIA</constant> (2),
 288 <constant>V4L2_COLORFX_NEGATIVE</constant> (3),
 289 <constant>V4L2_COLORFX_EMBOSS</constant> (4),
 290 <constant>V4L2_COLORFX_SKETCH</constant> (5),
 291 <constant>V4L2_COLORFX_SKY_BLUE</constant> (6),
 292 <constant>V4L2_COLORFX_GRASS_GREEN</constant> (7),
 293 <constant>V4L2_COLORFX_SKIN_WHITEN</constant> (8) and
 294 <constant>V4L2_COLORFX_VIVID</constant> (9).</entry>
 295           </row>
 296           <row>
 297             <entry><constant>V4L2_CID_ROTATE</constant></entry>
 298             <entry>integer</entry>
 299             <entry>Rotates the image by specified angle. Common angles are 90,
 300             270 and 180. Rotating the image to 90 and 270 will reverse the height
 301             and width of the display window. It is necessary to set the new height and
 302             width of the picture using the &VIDIOC-S-FMT; ioctl according to
 303             the rotation angle selected.</entry>
 304           </row>
 305           <row>
 306             <entry><constant>V4L2_CID_BG_COLOR</constant></entry>
 307             <entry>integer</entry>
 308             <entry>Sets the background color on the current output device.
 309             Background color needs to be specified in the RGB24 format. The
 310             supplied 32 bit value is interpreted as bits 0-7 Red color information,
 311             bits 8-15 Green color information, bits 16-23 Blue color
 312             information and bits 24-31 must be zero.</entry>
 313           </row>
 314           <row>
 315             <entry><constant>V4L2_CID_ILLUMINATORS_1</constant>
 316                 <constant>V4L2_CID_ILLUMINATORS_2</constant></entry>
 317             <entry>boolean</entry>
 318             <entry>Switch on or off the illuminator 1 or 2 of the device
 319                 (usually a microscope).</entry>
 320           </row>
 321           <row>
 322             <entry><constant>V4L2_CID_LASTP1</constant></entry>
 323             <entry></entry>
 324             <entry>End of the predefined control IDs (currently
 325 <constant>V4L2_CID_ILLUMINATORS_2</constant> + 1).</entry>
 326           </row>
 327           <row>
 328             <entry><constant>V4L2_CID_PRIVATE_BASE</constant></entry>
 329             <entry></entry>
 330             <entry>ID of the first custom (driver specific) control.
 331 Applications depending on particular custom controls should check the
 332 driver name and version, see <xref linkend="querycap" />.</entry>
 333           </row>
 334         </tbody>
 335       </tgroup>
 336     </table>
 337
 338     <para>Applications can enumerate the available controls with the
 339 &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls, get and set a
 340 control value with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls.
 341 Drivers must implement <constant>VIDIOC_QUERYCTRL</constant>,
 342 <constant>VIDIOC_G_CTRL</constant> and
 343 <constant>VIDIOC_S_CTRL</constant> when the device has one or more
 344 controls, <constant>VIDIOC_QUERYMENU</constant> when it has one or
 345 more menu type controls.</para>
 346
 347     <example>
 348       <title>Enumerating all controls</title>
 349
 350       <programlisting>
 351 &v4l2-queryctrl; queryctrl;
 352 &v4l2-querymenu; querymenu;
 353
 354 static void
 355 enumerate_menu (void)
 356 {
 357         printf ("  Menu items:\n");
 358
 359         memset (&amp;querymenu, 0, sizeof (querymenu));
 360         querymenu.id = queryctrl.id;
 361
 362         for (querymenu.index = queryctrl.minimum;
 363              querymenu.index &lt;= queryctrl.maximum;
 364               querymenu.index++) {
 365                 if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &amp;querymenu)) {
 366                         printf ("  %s\n", querymenu.name);
 367                 }
 368         }
 369 }
 370
 371 memset (&amp;queryctrl, 0, sizeof (queryctrl));
 372
 373 for (queryctrl.id = V4L2_CID_BASE;
 374      queryctrl.id &lt; V4L2_CID_LASTP1;
 375      queryctrl.id++) {
 376         if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 377                 if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
 378                         continue;
 379
 380                 printf ("Control %s\n", queryctrl.name);
 381
 382                 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
 383                         enumerate_menu ();
 384         } else {
 385                 if (errno == EINVAL)
 386                         continue;
 387
 388                 perror ("VIDIOC_QUERYCTRL");
 389                 exit (EXIT_FAILURE);
 390         }
 391 }
 392
 393 for (queryctrl.id = V4L2_CID_PRIVATE_BASE;;
 394      queryctrl.id++) {
 395         if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 396                 if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
 397                         continue;
 398
 399                 printf ("Control %s\n", queryctrl.name);
 400
 401                 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
 402                         enumerate_menu ();
 403         } else {
 404                 if (errno == EINVAL)
 405                         break;
 406
 407                 perror ("VIDIOC_QUERYCTRL");
 408                 exit (EXIT_FAILURE);
 409         }
 410 }
 411 </programlisting>
 412     </example>
 413
 414     <example>
 415       <title>Changing controls</title>
 416
 417       <programlisting>
 418 &v4l2-queryctrl; queryctrl;
 419 &v4l2-control; control;
 420
 421 memset (&amp;queryctrl, 0, sizeof (queryctrl));
 422 queryctrl.id = V4L2_CID_BRIGHTNESS;
 423
 424 if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 425         if (errno != EINVAL) {
 426                 perror ("VIDIOC_QUERYCTRL");
 427                 exit (EXIT_FAILURE);
 428         } else {
 429                 printf ("V4L2_CID_BRIGHTNESS is not supported\n");
 430         }
 431 } else if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED) {
 432         printf ("V4L2_CID_BRIGHTNESS is not supported\n");
 433 } else {
 434         memset (&amp;control, 0, sizeof (control));
 435         control.id = V4L2_CID_BRIGHTNESS;
 436         control.value = queryctrl.default_value;
 437
 438         if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)) {
 439                 perror ("VIDIOC_S_CTRL");
 440                 exit (EXIT_FAILURE);
 441         }
 442 }
 443
 444 memset (&amp;control, 0, sizeof (control));
 445 control.id = V4L2_CID_CONTRAST;
 446
 447 if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &amp;control)) {
 448         control.value += 1;
 449
 450         /* The driver may clamp the value or return ERANGE, ignored here */
 451
 452         if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)
 453             &amp;&amp; errno != ERANGE) {
 454                 perror ("VIDIOC_S_CTRL");
 455                 exit (EXIT_FAILURE);
 456         }
 457 /* Ignore if V4L2_CID_CONTRAST is unsupported */
 458 } else if (errno != EINVAL) {
 459         perror ("VIDIOC_G_CTRL");
 460         exit (EXIT_FAILURE);
 461 }
 462
 463 control.id = V4L2_CID_AUDIO_MUTE;
 464 control.value = TRUE; /* silence */
 465
 466 /* Errors ignored */
 467 ioctl (fd, VIDIOC_S_CTRL, &amp;control);
 468 </programlisting>
 469     </example>
 470   </section>
 471
 472   <section id="extended-controls">
 473     <title>Extended Controls</title>
 474
 475     <section>
 476       <title>Introduction</title>
 477
 478       <para>The control mechanism as originally designed was meant
 479 to be used for user settings (brightness, saturation, etc). However,
 480 it turned out to be a very useful model for implementing more
 481 complicated driver APIs where each driver implements only a subset of
 482 a larger API.</para>
 483
 484       <para>The MPEG encoding API was the driving force behind
 485 designing and implementing this extended control mechanism: the MPEG
 486 standard is quite large and the currently supported hardware MPEG
 487 encoders each only implement a subset of this standard. Further more,
 488 many parameters relating to how the video is encoded into an MPEG
 489 stream are specific to the MPEG encoding chip since the MPEG standard
 490 only defines the format of the resulting MPEG stream, not how the
 491 video is actually encoded into that format.</para>
 492
 493       <para>Unfortunately, the original control API lacked some
 494 features needed for these new uses and so it was extended into the
 495 (not terribly originally named) extended control API.</para>
 496
 497       <para>Even though the MPEG encoding API was the first effort
 498 to use the Extended Control API, nowadays there are also other classes
 499 of Extended Controls, such as Camera Controls and FM Transmitter Controls.
 500 The Extended Controls API as well as all Extended Controls classes are
 501 described in the following text.</para>
 502     </section>
 503
 504     <section>
 505       <title>The Extended Control API</title>
 506
 507       <para>Three new ioctls are available: &VIDIOC-G-EXT-CTRLS;,
 508 &VIDIOC-S-EXT-CTRLS; and &VIDIOC-TRY-EXT-CTRLS;. These ioctls act on
 509 arrays of controls (as opposed to the &VIDIOC-G-CTRL; and
 510 &VIDIOC-S-CTRL; ioctls that act on a single control). This is needed
 511 since it is often required to atomically change several controls at
 512 once.</para>
 513
 514       <para>Each of the new ioctls expects a pointer to a
 515 &v4l2-ext-controls;. This structure contains a pointer to the control
 516 array, a count of the number of controls in that array and a control
 517 class. Control classes are used to group similar controls into a
 518 single class. For example, control class
 519 <constant>V4L2_CTRL_CLASS_USER</constant> contains all user controls
 520 (&ie; all controls that can also be set using the old
 521 <constant>VIDIOC_S_CTRL</constant> ioctl). Control class
 522 <constant>V4L2_CTRL_CLASS_MPEG</constant> contains all controls
 523 relating to MPEG encoding, etc.</para>
 524
 525       <para>All controls in the control array must belong to the
 526 specified control class. An error is returned if this is not the
 527 case.</para>
 528
 529       <para>It is also possible to use an empty control array (count
 530 == 0) to check whether the specified control class is
 531 supported.</para>
 532
 533       <para>The control array is a &v4l2-ext-control; array. The
 534 <structname>v4l2_ext_control</structname> structure is very similar to
 535 &v4l2-control;, except for the fact that it also allows for 64-bit
 536 values and pointers to be passed.</para>
 537
 538       <para>It is important to realize that due to the flexibility of
 539 controls it is necessary to check whether the control you want to set
 540 actually is supported in the driver and what the valid range of values
 541 is. So use the &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls to
 542 check this. Also note that it is possible that some of the menu
 543 indices in a control of type <constant>V4L2_CTRL_TYPE_MENU</constant>
 544 may not be supported (<constant>VIDIOC_QUERYMENU</constant> will
 545 return an error). A good example is the list of supported MPEG audio
 546 bitrates. Some drivers only support one or two bitrates, others
 547 support a wider range.</para>
 548     </section>
 549
 550     <section>
 551       <title>Enumerating Extended Controls</title>
 552
 553       <para>The recommended way to enumerate over the extended
 554 controls is by using &VIDIOC-QUERYCTRL; in combination with the
 555 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag:</para>
 556
 557       <informalexample>
 558         <programlisting>
 559 &v4l2-queryctrl; qctrl;
 560
 561 qctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
 562 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
 563         /* ... */
 564         qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
 565 }
 566 </programlisting>
 567       </informalexample>
 568
 569       <para>The initial control ID is set to 0 ORed with the
 570 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag. The
 571 <constant>VIDIOC_QUERYCTRL</constant> ioctl will return the first
 572 control with a higher ID than the specified one. When no such controls
 573 are found an error is returned.</para>
 574
 575       <para>If you want to get all controls within a specific control
 576 class, then you can set the initial
 577 <structfield>qctrl.id</structfield> value to the control class and add
 578 an extra check to break out of the loop when a control of another
 579 control class is found:</para>
 580
 581       <informalexample>
 582         <programlisting>
 583 qctrl.id = V4L2_CTRL_CLASS_MPEG | V4L2_CTRL_FLAG_NEXT_CTRL;
 584 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
 585         if (V4L2_CTRL_ID2CLASS (qctrl.id) != V4L2_CTRL_CLASS_MPEG)
 586                 break;
 587                 /* ... */
 588                 qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
 589         }
 590 </programlisting>
 591       </informalexample>
 592
 593       <para>The 32-bit <structfield>qctrl.id</structfield> value is
 594 subdivided into three bit ranges: the top 4 bits are reserved for
 595 flags (&eg; <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>) and are not
 596 actually part of the ID. The remaining 28 bits form the control ID, of
 597 which the most significant 12 bits define the control class and the
 598 least significant 16 bits identify the control within the control
 599 class. It is guaranteed that these last 16 bits are always non-zero
 600 for controls. The range of 0x1000 and up are reserved for
 601 driver-specific controls. The macro
 602 <constant>V4L2_CTRL_ID2CLASS(id)</constant> returns the control class
 603 ID based on a control ID.</para>
 604
 605       <para>If the driver does not support extended controls, then
 606 <constant>VIDIOC_QUERYCTRL</constant> will fail when used in
 607 combination with <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>. In
 608 that case the old method of enumerating control should be used (see
 609 1.8). But if it is supported, then it is guaranteed to enumerate over
 610 all controls, including driver-private controls.</para>
 611     </section>
 612
 613     <section>
 614       <title>Creating Control Panels</title>
 615
 616       <para>It is possible to create control panels for a graphical
 617 user interface where the user can select the various controls.
 618 Basically you will have to iterate over all controls using the method
 619 described above. Each control class starts with a control of type
 620 <constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant>.
 621 <constant>VIDIOC_QUERYCTRL</constant> will return the name of this
 622 control class which can be used as the title of a tab page within a
 623 control panel.</para>
 624
 625       <para>The flags field of &v4l2-queryctrl; also contains hints on
 626 the behavior of the control. See the &VIDIOC-QUERYCTRL; documentation
 627 for more details.</para>
 628     </section>
 629
 630     <section id="mpeg-controls">
 631       <title>MPEG Control Reference</title>
 632
 633       <para>Below all controls within the MPEG control class are
 634 described. First the generic controls, then controls specific for
 635 certain hardware.</para>
 636
 637       <section>
 638         <title>Generic MPEG Controls</title>
 639
 640         <table pgwide="1" frame="none" id="mpeg-control-id">
 641           <title>MPEG Control IDs</title>
 642           <tgroup cols="4">
 643             <colspec colname="c1" colwidth="1*" />
 644             <colspec colname="c2" colwidth="6*" />
 645             <colspec colname="c3" colwidth="2*" />
 646             <colspec colname="c4" colwidth="6*" />
 647             <spanspec namest="c1" nameend="c2" spanname="id" />
 648             <spanspec namest="c2" nameend="c4" spanname="descr" />
 649             <thead>
 650               <row>
 651                 <entry spanname="id" align="left">ID</entry>
 652                 <entry align="left">Type</entry>
 653               </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
 654               </row>
 655             </thead>
 656             <tbody valign="top">
 657               <row><entry></entry></row>
 658               <row>
 659                 <entry spanname="id"><constant>V4L2_CID_MPEG_CLASS</constant>&nbsp;</entry>
 660                 <entry>class</entry>
 661               </row><row><entry spanname="descr">The MPEG class
 662 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
 663 description of this control class. This description can be used as the
 664 caption of a Tab page in a GUI, for example.</entry>
 665               </row>
 666               <row><entry></entry></row>
 667               <row id="v4l2-mpeg-stream-type">
 668                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_TYPE</constant>&nbsp;</entry>
 669                 <entry>enum&nbsp;v4l2_mpeg_stream_type</entry>
 670               </row><row><entry spanname="descr">The MPEG-1, -2 or -4
 671 output stream type. One cannot assume anything here. Each hardware
 672 MPEG encoder tends to support different subsets of the available MPEG
 673 stream types. The currently defined stream types are:</entry>
 674               </row>
 675               <row>
 676                 <entrytbl spanname="descr" cols="2">
 677                   <tbody valign="top">
 678                     <row>
 679                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_PS</constant>&nbsp;</entry>
 680                       <entry>MPEG-2 program stream</entry>
 681                     </row>
 682                     <row>
 683                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_TS</constant>&nbsp;</entry>
 684                       <entry>MPEG-2 transport stream</entry>
 685                     </row>
 686                     <row>
 687                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_SS</constant>&nbsp;</entry>
 688                       <entry>MPEG-1 system stream</entry>
 689                     </row>
 690                     <row>
 691                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_DVD</constant>&nbsp;</entry>
 692                       <entry>MPEG-2 DVD-compatible stream</entry>
 693                     </row>
 694                     <row>
 695                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_VCD</constant>&nbsp;</entry>
 696                       <entry>MPEG-1 VCD-compatible stream</entry>
 697                     </row>
 698                     <row>
 699                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_SVCD</constant>&nbsp;</entry>
 700                       <entry>MPEG-2 SVCD-compatible stream</entry>
 701                     </row>
 702                   </tbody>
 703                 </entrytbl>
 704               </row>
 705               <row><entry></entry></row>
 706               <row>
 707                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PMT</constant>&nbsp;</entry>
 708                 <entry>integer</entry>
 709               </row><row><entry spanname="descr">Program Map Table
 710 Packet ID for the MPEG transport stream (default 16)</entry>
 711               </row>
 712               <row><entry></entry></row>
 713               <row>
 714                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_AUDIO</constant>&nbsp;</entry>
 715                 <entry>integer</entry>
 716               </row><row><entry spanname="descr">Audio Packet ID for
 717 the MPEG transport stream (default 256)</entry>
 718               </row>
 719               <row><entry></entry></row>
 720               <row>
 721                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_VIDEO</constant>&nbsp;</entry>
 722                 <entry>integer</entry>
 723               </row><row><entry spanname="descr">Video Packet ID for
 724 the MPEG transport stream (default 260)</entry>
 725               </row>
 726               <row><entry></entry></row>
 727               <row>
 728                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PCR</constant>&nbsp;</entry>
 729                 <entry>integer</entry>
 730               </row><row><entry spanname="descr">Packet ID for the
 731 MPEG transport stream carrying PCR fields (default 259)</entry>
 732               </row>
 733               <row><entry></entry></row>
 734               <row>
 735                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_AUDIO</constant>&nbsp;</entry>
 736                 <entry>integer</entry>
 737               </row><row><entry spanname="descr">Audio ID for MPEG
 738 PES</entry>
 739               </row>
 740               <row><entry></entry></row>
 741               <row>
 742                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_VIDEO</constant>&nbsp;</entry>
 743                 <entry>integer</entry>
 744               </row><row><entry spanname="descr">Video ID for MPEG
 745 PES</entry>
 746               </row>
 747               <row><entry></entry></row>
 748               <row id="v4l2-mpeg-stream-vbi-fmt">
 749                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_VBI_FMT</constant>&nbsp;</entry>
 750                 <entry>enum&nbsp;v4l2_mpeg_stream_vbi_fmt</entry>
 751               </row><row><entry spanname="descr">Some cards can embed
 752 VBI data (&eg; Closed Caption, Teletext) into the MPEG stream. This
 753 control selects whether VBI data should be embedded, and if so, what
 754 embedding method should be used. The list of possible VBI formats
 755 depends on the driver. The currently defined VBI format types
 756 are:</entry>
 757               </row>
 758               <row>
 759                 <entrytbl spanname="descr" cols="2">
 760                   <tbody valign="top">
 761                     <row>
 762                       <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_NONE</constant>&nbsp;</entry>
 763                       <entry>No VBI in the MPEG stream</entry>
 764                     </row>
 765                     <row>
 766                       <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant>&nbsp;</entry>
 767                       <entry>VBI in private packets, IVTV format (documented
 768 in the kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.vbi</filename>)</entry>
 769                     </row>
 770                   </tbody>
 771                 </entrytbl>
 772               </row>
 773               <row><entry></entry></row>
 774               <row id="v4l2-mpeg-audio-sampling-freq">
 775                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ</constant>&nbsp;</entry>
 776                 <entry>enum&nbsp;v4l2_mpeg_audio_sampling_freq</entry>
 777               </row><row><entry spanname="descr">MPEG Audio sampling
 778 frequency. Possible values are:</entry>
 779               </row>
 780               <row>
 781                 <entrytbl spanname="descr" cols="2">
 782                   <tbody valign="top">
 783                     <row>
 784                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_44100</constant>&nbsp;</entry>
 785                       <entry>44.1 kHz</entry>
 786                     </row>
 787                     <row>
 788                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_48000</constant>&nbsp;</entry>
 789                       <entry>48 kHz</entry>
 790                     </row>
 791                     <row>
 792                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_32000</constant>&nbsp;</entry>
 793                       <entry>32 kHz</entry>
 794                     </row>
 795                   </tbody>
 796                 </entrytbl>
 797               </row>
 798               <row><entry></entry></row>
 799               <row id="v4l2-mpeg-audio-encoding">
 800                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_ENCODING</constant>&nbsp;</entry>
 801                 <entry>enum&nbsp;v4l2_mpeg_audio_encoding</entry>
 802               </row><row><entry spanname="descr">MPEG Audio encoding.
 803 Possible values are:</entry>
 804               </row>
 805               <row>
 806                 <entrytbl spanname="descr" cols="2">
 807                   <tbody valign="top">
 808                     <row>
 809                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_1</constant>&nbsp;</entry>
 810                       <entry>MPEG-1/2 Layer I encoding</entry>
 811                     </row>
 812                     <row>
 813                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_2</constant>&nbsp;</entry>
 814                       <entry>MPEG-1/2 Layer II encoding</entry>
 815                     </row>
 816                     <row>
 817                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_3</constant>&nbsp;</entry>
 818                       <entry>MPEG-1/2 Layer III encoding</entry>
 819                     </row>
 820                     <row>
 821                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant>&nbsp;</entry>
 822                       <entry>MPEG-2/4 AAC (Advanced Audio Coding)</entry>
 823                     </row>
 824                     <row>
 825                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant>&nbsp;</entry>
 826                       <entry>AC-3 aka ATSC A/52 encoding</entry>
 827                     </row>
 828                   </tbody>
 829                 </entrytbl>
 830               </row>
 831               <row><entry></entry></row>
 832               <row id="v4l2-mpeg-audio-l1-bitrate">
 833                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L1_BITRATE</constant>&nbsp;</entry>
 834                 <entry>enum&nbsp;v4l2_mpeg_audio_l1_bitrate</entry>
 835               </row><row><entry spanname="descr">MPEG-1/2 Layer I bitrate.
 836 Possible values are:</entry>
 837               </row>
 838               <row>
 839                 <entrytbl spanname="descr" cols="2">
 840                   <tbody valign="top">
 841                     <row>
 842                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_32K</constant>&nbsp;</entry>
 843                       <entry>32 kbit/s</entry></row>
 844                     <row>
 845                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_64K</constant>&nbsp;</entry>
 846                       <entry>64 kbit/s</entry>
 847                     </row>
 848                     <row>
 849                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_96K</constant>&nbsp;</entry>
 850                       <entry>96 kbit/s</entry>
 851                     </row>
 852                     <row>
 853                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_128K</constant>&nbsp;</entry>
 854                       <entry>128 kbit/s</entry>
 855                     </row>
 856                     <row>
 857                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_160K</constant>&nbsp;</entry>
 858                       <entry>160 kbit/s</entry>
 859                     </row>
 860                     <row>
 861                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_192K</constant>&nbsp;</entry>
 862                       <entry>192 kbit/s</entry>
 863                     </row>
 864                     <row>
 865                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_224K</constant>&nbsp;</entry>
 866                       <entry>224 kbit/s</entry>
 867                     </row>
 868                     <row>
 869                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_256K</constant>&nbsp;</entry>
 870                       <entry>256 kbit/s</entry>
 871                     </row>
 872                     <row>
 873                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_288K</constant>&nbsp;</entry>
 874                       <entry>288 kbit/s</entry>
 875                     </row>
 876                     <row>
 877                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_320K</constant>&nbsp;</entry>
 878                       <entry>320 kbit/s</entry>
 879                     </row>
 880                     <row>
 881                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_352K</constant>&nbsp;</entry>
 882                       <entry>352 kbit/s</entry>
 883                     </row>
 884                     <row>
 885                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_384K</constant>&nbsp;</entry>
 886                       <entry>384 kbit/s</entry>
 887                     </row>
 888                     <row>
 889                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_416K</constant>&nbsp;</entry>
 890                       <entry>416 kbit/s</entry>
 891                     </row>
 892                     <row>
 893                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_448K</constant>&nbsp;</entry>
 894                       <entry>448 kbit/s</entry>
 895                     </row>
 896                   </tbody>
 897                 </entrytbl>
 898               </row>
 899               <row><entry></entry></row>
 900               <row id="v4l2-mpeg-audio-l2-bitrate">
 901                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L2_BITRATE</constant>&nbsp;</entry>
 902                 <entry>enum&nbsp;v4l2_mpeg_audio_l2_bitrate</entry>
 903               </row><row><entry spanname="descr">MPEG-1/2 Layer II bitrate.
 904 Possible values are:</entry>
 905               </row>
 906               <row>
 907                 <entrytbl spanname="descr" cols="2">
 908                   <tbody valign="top">
 909                     <row>
 910                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_32K</constant>&nbsp;</entry>
 911                       <entry>32 kbit/s</entry>
 912                     </row>
 913                     <row>
 914                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_48K</constant>&nbsp;</entry>
 915                       <entry>48 kbit/s</entry>
 916                     </row>
 917                     <row>
 918                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_56K</constant>&nbsp;</entry>
 919                       <entry>56 kbit/s</entry>
 920                     </row>
 921                     <row>
 922                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_64K</constant>&nbsp;</entry>
 923                       <entry>64 kbit/s</entry>
 924                     </row>
 925                     <row>
 926                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_80K</constant>&nbsp;</entry>
 927                       <entry>80 kbit/s</entry>
 928                     </row>
 929                     <row>
 930                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_96K</constant>&nbsp;</entry>
 931                       <entry>96 kbit/s</entry>
 932                     </row>
 933                     <row>
 934                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_112K</constant>&nbsp;</entry>
 935                       <entry>112 kbit/s</entry>
 936                     </row>
 937                     <row>
 938                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_128K</constant>&nbsp;</entry>
 939                       <entry>128 kbit/s</entry>
 940                     </row>
 941                     <row>
 942                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_160K</constant>&nbsp;</entry>
 943                       <entry>160 kbit/s</entry>
 944                     </row>
 945                     <row>
 946                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_192K</constant>&nbsp;</entry>
 947                       <entry>192 kbit/s</entry>
 948                     </row>
 949                     <row>
 950                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_224K</constant>&nbsp;</entry>
 951                       <entry>224 kbit/s</entry>
 952                     </row>
 953                     <row>
 954                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_256K</constant>&nbsp;</entry>
 955                       <entry>256 kbit/s</entry>
 956                     </row>
 957                     <row>
 958                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_320K</constant>&nbsp;</entry>
 959                       <entry>320 kbit/s</entry>
 960                     </row>
 961                     <row>
 962                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_384K</constant>&nbsp;</entry>
 963                       <entry>384 kbit/s</entry>
 964                     </row>
 965                   </tbody>
 966                 </entrytbl>
 967               </row>
 968               <row><entry></entry></row>
 969               <row id="v4l2-mpeg-audio-l3-bitrate">
 970                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L3_BITRATE</constant>&nbsp;</entry>
 971                 <entry>enum&nbsp;v4l2_mpeg_audio_l3_bitrate</entry>
 972               </row><row><entry spanname="descr">MPEG-1/2 Layer III bitrate.
 973 Possible values are:</entry>
 974               </row>
 975               <row>
 976                 <entrytbl spanname="descr" cols="2">
 977                   <tbody valign="top">
 978                     <row>
 979                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_32K</constant>&nbsp;</entry>
 980                       <entry>32 kbit/s</entry>
 981                     </row>
 982                     <row>
 983                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_40K</constant>&nbsp;</entry>
 984                       <entry>40 kbit/s</entry>
 985                     </row>
 986                     <row>
 987                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_48K</constant>&nbsp;</entry>
 988                       <entry>48 kbit/s</entry>
 989                     </row>
 990                     <row>
 991                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_56K</constant>&nbsp;</entry>
 992                       <entry>56 kbit/s</entry>
 993                     </row>
 994                     <row>
 995                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_64K</constant>&nbsp;</entry>
 996                       <entry>64 kbit/s</entry>
 997                     </row>
 998                     <row>
 999                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_80K</constant>&nbsp;</entry>
1000                       <entry>80 kbit/s</entry>
1001                     </row>
1002                     <row>
1003                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_96K</constant>&nbsp;</entry>
1004                       <entry>96 kbit/s</entry>
1005                     </row>
1006                     <row>
1007                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_112K</constant>&nbsp;</entry>
1008                       <entry>112 kbit/s</entry>
1009                     </row>
1010                     <row>
1011                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_128K</constant>&nbsp;</entry>
1012                       <entry>128 kbit/s</entry>
1013                     </row>
1014                     <row>
1015                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_160K</constant>&nbsp;</entry>
1016                       <entry>160 kbit/s</entry>
1017                     </row>
1018                     <row>
1019                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_192K</constant>&nbsp;</entry>
1020                       <entry>192 kbit/s</entry>
1021                     </row>
1022                     <row>
1023                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_224K</constant>&nbsp;</entry>
1024                       <entry>224 kbit/s</entry>
1025                     </row>
1026                     <row>
1027                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_256K</constant>&nbsp;</entry>
1028                       <entry>256 kbit/s</entry>
1029                     </row>
1030                     <row>
1031                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_320K</constant>&nbsp;</entry>
1032                       <entry>320 kbit/s</entry>
1033                     </row>
1034                   </tbody>
1035                 </entrytbl>
1036               </row>
1037               <row><entry></entry></row>
1038               <row>
1039                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AAC_BITRATE</constant>&nbsp;</entry>
1040                 <entry>integer</entry>
1041               </row><row><entry spanname="descr">AAC bitrate in bits per second.</entry>
1042               </row>
1043               <row><entry></entry></row>
1044               <row id="v4l2-mpeg-audio-ac3-bitrate">
1045                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AC3_BITRATE</constant>&nbsp;</entry>
1046                 <entry>enum&nbsp;v4l2_mpeg_audio_ac3_bitrate</entry>
1047               </row><row><entry spanname="descr">AC-3 bitrate.
1048 Possible values are:</entry>
1049               </row>
1050               <row>
1051                 <entrytbl spanname="descr" cols="2">
1052                   <tbody valign="top">
1053                     <row>
1054                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_32K</constant>&nbsp;</entry>
1055                       <entry>32 kbit/s</entry>
1056                     </row>
1057                     <row>
1058                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_40K</constant>&nbsp;</entry>
1059                       <entry>40 kbit/s</entry>
1060                     </row>
1061                     <row>
1062                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_48K</constant>&nbsp;</entry>
1063                       <entry>48 kbit/s</entry>
1064                     </row>
1065                     <row>
1066                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_56K</constant>&nbsp;</entry>
1067                       <entry>56 kbit/s</entry>
1068                     </row>
1069                     <row>
1070                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_64K</constant>&nbsp;</entry>
1071                       <entry>64 kbit/s</entry>
1072                     </row>
1073                     <row>
1074                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_80K</constant>&nbsp;</entry>
1075                       <entry>80 kbit/s</entry>
1076                     </row>
1077                     <row>
1078                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_96K</constant>&nbsp;</entry>
1079                       <entry>96 kbit/s</entry>
1080                     </row>
1081                     <row>
1082                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_112K</constant>&nbsp;</entry>
1083                       <entry>112 kbit/s</entry>
1084                     </row>
1085                     <row>
1086                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_128K</constant>&nbsp;</entry>
1087                       <entry>128 kbit/s</entry>
1088                     </row>
1089                     <row>
1090                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_160K</constant>&nbsp;</entry>
1091                       <entry>160 kbit/s</entry>
1092                     </row>
1093                     <row>
1094                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_192K</constant>&nbsp;</entry>
1095                       <entry>192 kbit/s</entry>
1096                     </row>
1097                     <row>
1098                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_224K</constant>&nbsp;</entry>
1099                       <entry>224 kbit/s</entry>
1100                     </row>
1101                     <row>
1102                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_256K</constant>&nbsp;</entry>
1103                       <entry>256 kbit/s</entry>
1104                     </row>
1105                     <row>
1106                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_320K</constant>&nbsp;</entry>
1107                       <entry>320 kbit/s</entry>
1108                     </row>
1109                     <row>
1110                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_384K</constant>&nbsp;</entry>
1111                       <entry>384 kbit/s</entry>
1112                     </row>
1113                     <row>
1114                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_448K</constant>&nbsp;</entry>
1115                       <entry>448 kbit/s</entry>
1116                     </row>
1117                     <row>
1118                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_512K</constant>&nbsp;</entry>
1119                       <entry>512 kbit/s</entry>
1120                     </row>
1121                     <row>
1122                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_576K</constant>&nbsp;</entry>
1123                       <entry>576 kbit/s</entry>
1124                     </row>
1125                     <row>
1126                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_640K</constant>&nbsp;</entry>
1127                       <entry>640 kbit/s</entry>
1128                     </row>
1129                   </tbody>
1130                 </entrytbl>
1131               </row>
1132               <row><entry></entry></row>
1133               <row id="v4l2-mpeg-audio-mode">
1134                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE</constant>&nbsp;</entry>
1135                 <entry>enum&nbsp;v4l2_mpeg_audio_mode</entry>
1136               </row><row><entry spanname="descr">MPEG Audio mode.
1137 Possible values are:</entry>
1138               </row>
1139               <row>
1140                 <entrytbl spanname="descr" cols="2">
1141                   <tbody valign="top">
1142                     <row>
1143                       <entry><constant>V4L2_MPEG_AUDIO_MODE_STEREO</constant>&nbsp;</entry>
1144                       <entry>Stereo</entry>
1145                     </row>
1146                     <row>
1147                       <entry><constant>V4L2_MPEG_AUDIO_MODE_JOINT_STEREO</constant>&nbsp;</entry>
1148                       <entry>Joint Stereo</entry>
1149                     </row>
1150                     <row>
1151                       <entry><constant>V4L2_MPEG_AUDIO_MODE_DUAL</constant>&nbsp;</entry>
1152                       <entry>Bilingual</entry>
1153                     </row>
1154                     <row>
1155                       <entry><constant>V4L2_MPEG_AUDIO_MODE_MONO</constant>&nbsp;</entry>
1156                       <entry>Mono</entry>
1157                     </row>
1158                   </tbody>
1159                 </entrytbl>
1160               </row>
1161               <row><entry></entry></row>
1162               <row id="v4l2-mpeg-audio-mode-extension">
1163                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE_EXTENSION</constant>&nbsp;</entry>
1164                 <entry>enum&nbsp;v4l2_mpeg_audio_mode_extension</entry>
1165               </row><row><entry spanname="descr">Joint Stereo
1166 audio mode extension. In Layer I and II they indicate which subbands
1167 are in intensity stereo. All other subbands are coded in stereo. Layer
1168 III is not (yet) supported. Possible values
1169 are:</entry>
1170               </row>
1171               <row>
1172                 <entrytbl spanname="descr" cols="2">
1173                   <tbody valign="top">
1174                     <row>
1175                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_4</constant>&nbsp;</entry>
1176                       <entry>Subbands 4-31 in intensity stereo</entry>
1177                     </row>
1178                     <row>
1179                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_8</constant>&nbsp;</entry>
1180                       <entry>Subbands 8-31 in intensity stereo</entry>
1181                     </row>
1182                     <row>
1183                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_12</constant>&nbsp;</entry>
1184                       <entry>Subbands 12-31 in intensity stereo</entry>
1185                     </row>
1186                     <row>
1187                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_16</constant>&nbsp;</entry>
1188                       <entry>Subbands 16-31 in intensity stereo</entry>
1189                     </row>
1190                   </tbody>
1191                 </entrytbl>
1192               </row>
1193               <row><entry></entry></row>
1194               <row id="v4l2-mpeg-audio-emphasis">
1195                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_EMPHASIS</constant>&nbsp;</entry>
1196                 <entry>enum&nbsp;v4l2_mpeg_audio_emphasis</entry>
1197               </row><row><entry spanname="descr">Audio Emphasis.
1198 Possible values are:</entry>
1199               </row>
1200               <row>
1201                 <entrytbl spanname="descr" cols="2">
1202                   <tbody valign="top">
1203                     <row>
1204                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_NONE</constant>&nbsp;</entry>
1205                       <entry>None</entry>
1206                     </row>
1207                     <row>
1208                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_50_DIV_15_uS</constant>&nbsp;</entry>
1209                       <entry>50/15 microsecond emphasis</entry>
1210                     </row>
1211                     <row>
1212                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_CCITT_J17</constant>&nbsp;</entry>
1213                       <entry>CCITT J.17</entry>
1214                     </row>
1215                   </tbody>
1216                 </entrytbl>
1217               </row>
1218               <row><entry></entry></row>
1219               <row id="v4l2-mpeg-audio-crc">
1220                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_CRC</constant>&nbsp;</entry>
1221                 <entry>enum&nbsp;v4l2_mpeg_audio_crc</entry>
1222               </row><row><entry spanname="descr">CRC method. Possible
1223 values are:</entry>
1224               </row>
1225               <row>
1226                 <entrytbl spanname="descr" cols="2">
1227                   <tbody valign="top">
1228                     <row>
1229                       <entry><constant>V4L2_MPEG_AUDIO_CRC_NONE</constant>&nbsp;</entry>
1230                       <entry>None</entry>
1231                     </row>
1232                     <row>
1233                       <entry><constant>V4L2_MPEG_AUDIO_CRC_CRC16</constant>&nbsp;</entry>
1234                       <entry>16 bit parity check</entry>
1235                     </row>
1236                   </tbody>
1237                 </entrytbl>
1238               </row>
1239               <row><entry></entry></row>
1240               <row>
1241                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MUTE</constant>&nbsp;</entry>
1242                 <entry>boolean</entry>
1243               </row><row><entry spanname="descr">Mutes the audio when
1244 capturing. This is not done by muting audio hardware, which can still
1245 produce a slight hiss, but in the encoder itself, guaranteeing a fixed
1246 and reproducible audio bitstream. 0 = unmuted, 1 = muted.</entry>
1247               </row>
1248               <row><entry></entry></row>
1249               <row id="v4l2-mpeg-video-encoding">
1250                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ENCODING</constant>&nbsp;</entry>
1251                 <entry>enum&nbsp;v4l2_mpeg_video_encoding</entry>
1252               </row><row><entry spanname="descr">MPEG Video encoding
1253 method. Possible values are:</entry>
1254               </row>
1255               <row>
1256                 <entrytbl spanname="descr" cols="2">
1257                   <tbody valign="top">
1258                     <row>
1259                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_1</constant>&nbsp;</entry>
1260                       <entry>MPEG-1 Video encoding</entry>
1261                     </row>
1262                     <row>
1263                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_2</constant>&nbsp;</entry>
1264                       <entry>MPEG-2 Video encoding</entry>
1265                     </row>
1266                     <row>
1267                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant>&nbsp;</entry>
1268                       <entry>MPEG-4 AVC (H.264) Video encoding</entry>
1269                     </row>
1270                   </tbody>
1271                 </entrytbl>
1272               </row>
1273               <row><entry></entry></row>
1274               <row id="v4l2-mpeg-video-aspect">
1275                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ASPECT</constant>&nbsp;</entry>
1276                 <entry>enum&nbsp;v4l2_mpeg_video_aspect</entry>
1277               </row><row><entry spanname="descr">Video aspect.
1278 Possible values are:</entry>
1279               </row>
1280               <row>
1281                 <entrytbl spanname="descr" cols="2">
1282                   <tbody valign="top">
1283                     <row>
1284                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_1x1</constant>&nbsp;</entry>
1285                     </row>
1286                     <row>
1287                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_4x3</constant>&nbsp;</entry>
1288                     </row>
1289                     <row>
1290                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_16x9</constant>&nbsp;</entry>
1291                     </row>
1292                     <row>
1293                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_221x100</constant>&nbsp;</entry>
1294                     </row>
1295                   </tbody>
1296                 </entrytbl>
1297               </row>
1298               <row><entry></entry></row>
1299               <row>
1300                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_B_FRAMES</constant>&nbsp;</entry>
1301                 <entry>integer</entry>
1302               </row><row><entry spanname="descr">Number of B-Frames
1303 (default 2)</entry>
1304               </row>
1305               <row><entry></entry></row>
1306               <row>
1307                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_SIZE</constant>&nbsp;</entry>
1308                 <entry>integer</entry>
1309               </row><row><entry spanname="descr">GOP size (default
1310 12)</entry>
1311               </row>
1312               <row><entry></entry></row>
1313               <row>
1314                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_CLOSURE</constant>&nbsp;</entry>
1315                 <entry>boolean</entry>
1316               </row><row><entry spanname="descr">GOP closure (default
1317 1)</entry>
1318               </row>
1319               <row><entry></entry></row>
1320               <row>
1321                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_PULLDOWN</constant>&nbsp;</entry>
1322                 <entry>boolean</entry>
1323               </row><row><entry spanname="descr">Enable 3:2 pulldown
1324 (default 0)</entry>
1325               </row>
1326               <row><entry></entry></row>
1327               <row id="v4l2-mpeg-video-bitrate-mode">
1328                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_MODE</constant>&nbsp;</entry>
1329                 <entry>enum&nbsp;v4l2_mpeg_video_bitrate_mode</entry>
1330               </row><row><entry spanname="descr">Video bitrate mode.
1331 Possible values are:</entry>
1332               </row>
1333               <row>
1334                 <entrytbl spanname="descr" cols="2">
1335                   <tbody valign="top">
1336                     <row>
1337                       <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_VBR</constant>&nbsp;</entry>
1338                       <entry>Variable bitrate</entry>
1339                     </row>
1340                     <row>
1341                       <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_CBR</constant>&nbsp;</entry>
1342                       <entry>Constant bitrate</entry>
1343                     </row>
1344                   </tbody>
1345                 </entrytbl>
1346               </row>
1347               <row><entry></entry></row>
1348               <row>
1349                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE</constant>&nbsp;</entry>
1350                 <entry>integer</entry>
1351               </row><row><entry spanname="descr">Video bitrate in bits
1352 per second.</entry>
1353               </row>
1354               <row><entry></entry></row>
1355               <row>
1356                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_PEAK</constant>&nbsp;</entry>
1357                 <entry>integer</entry>
1358               </row><row><entry spanname="descr">Peak video bitrate in
1359 bits per second. Must be larger or equal to the average video bitrate.
1360 It is ignored if the video bitrate mode is set to constant
1361 bitrate.</entry>
1362               </row>
1363               <row><entry></entry></row>
1364               <row>
1365                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION</constant>&nbsp;</entry>
1366                 <entry>integer</entry>
1367               </row><row><entry spanname="descr">For every captured
1368 frame, skip this many subsequent frames (default 0).</entry>
1369               </row>
1370               <row><entry></entry></row>
1371               <row>
1372                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE</constant>&nbsp;</entry>
1373                 <entry>boolean</entry>
1374               </row>
1375               <row><entry spanname="descr">"Mutes" the video to a
1376 fixed color when capturing. This is useful for testing, to produce a
1377 fixed video bitstream. 0 = unmuted, 1 = muted.</entry>
1378               </row>
1379               <row><entry></entry></row>
1380               <row>
1381                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE_YUV</constant>&nbsp;</entry>
1382                 <entry>integer</entry>
1383               </row><row><entry spanname="descr">Sets the "mute" color
1384 of the video. The supplied 32-bit integer is interpreted as follows (bit
1385 0 = least significant bit):</entry>
1386               </row>
1387               <row>
1388                 <entrytbl spanname="descr" cols="2">
1389                   <tbody valign="top">
1390                     <row>
1391                       <entry>Bit 0:7</entry>
1392                       <entry>V chrominance information</entry>
1393                     </row>
1394                     <row>
1395                       <entry>Bit 8:15</entry>
1396                       <entry>U chrominance information</entry>
1397                     </row>
1398                     <row>
1399                       <entry>Bit 16:23</entry>
1400                       <entry>Y luminance information</entry>
1401                     </row>
1402                     <row>
1403                       <entry>Bit 24:31</entry>
1404                       <entry>Must be zero.</entry>
1405                     </row>
1406                   </tbody>
1407                 </entrytbl>
1408               </row>
1409             </tbody>
1410           </tgroup>
1411         </table>
1412       </section>
1413
1414       <section>
1415         <title>CX2341x MPEG Controls</title>
1416
1417         <para>The following MPEG class controls deal with MPEG
1418 encoding settings that are specific to the Conexant CX23415 and
1419 CX23416 MPEG encoding chips.</para>
1420
1421         <table pgwide="1" frame="none" id="cx2341x-control-id">
1422           <title>CX2341x Control IDs</title>
1423           <tgroup cols="4">
1424             <colspec colname="c1" colwidth="1*" />
1425             <colspec colname="c2" colwidth="6*" />
1426             <colspec colname="c3" colwidth="2*" />
1427             <colspec colname="c4" colwidth="6*" />
1428             <spanspec namest="c1" nameend="c2" spanname="id" />
1429             <spanspec namest="c2" nameend="c4" spanname="descr" />
1430             <thead>
1431               <row>
1432                 <entry spanname="id" align="left">ID</entry>
1433                 <entry align="left">Type</entry>
1434               </row><row><entry spanname="descr" align="left">Description</entry>
1435               </row>
1436             </thead>
1437             <tbody valign="top">
1438               <row><entry></entry></row>
1439               <row id="v4l2-mpeg-cx2341x-video-spatial-filter-mode">
1440                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE</constant>&nbsp;</entry>
1441                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_spatial_filter_mode</entry>
1442               </row><row><entry spanname="descr">Sets the Spatial
1443 Filter mode (default <constant>MANUAL</constant>). Possible values
1444 are:</entry>
1445               </row>
1446               <row>
1447                 <entrytbl spanname="descr" cols="2">
1448                   <tbody valign="top">
1449                     <row>
1450                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1451                       <entry>Choose the filter manually</entry>
1452                     </row>
1453                     <row>
1454                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1455                       <entry>Choose the filter automatically</entry>
1456                     </row>
1457                   </tbody>
1458                 </entrytbl>
1459               </row>
1460               <row><entry></entry></row>
1461               <row>
1462                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER</constant>&nbsp;</entry>
1463                 <entry>integer&nbsp;(0-15)</entry>
1464               </row><row><entry spanname="descr">The setting for the
1465 Spatial Filter. 0 = off, 15 = maximum. (Default is 0.)</entry>
1466               </row>
1467               <row><entry></entry></row>
1468               <row id="luma-spatial-filter-type">
1469                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1470                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_luma_spatial_filter_type</entry>
1471               </row><row><entry spanname="descr">Select the algorithm
1472 to use for the Luma Spatial Filter (default
1473 <constant>1D_HOR</constant>). Possible values:</entry>
1474               </row>
1475               <row>
1476                 <entrytbl spanname="descr" cols="2">
1477                   <tbody valign="top">
1478                     <row>
1479                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1480                       <entry>No filter</entry>
1481                     </row>
1482                     <row>
1483                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1484                       <entry>One-dimensional horizontal</entry>
1485                     </row>
1486                     <row>
1487                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_VERT</constant>&nbsp;</entry>
1488                       <entry>One-dimensional vertical</entry>
1489                     </row>
1490                     <row>
1491                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_HV_SEPARABLE</constant>&nbsp;</entry>
1492                       <entry>Two-dimensional separable</entry>
1493                     </row>
1494                     <row>
1495                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_SYM_NON_SEPARABLE</constant>&nbsp;</entry>
1496                       <entry>Two-dimensional symmetrical
1497 non-separable</entry>
1498                     </row>
1499                   </tbody>
1500                 </entrytbl>
1501               </row>
1502               <row><entry></entry></row>
1503               <row id="chroma-spatial-filter-type">
1504                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1505                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_chroma_spatial_filter_type</entry>
1506               </row><row><entry spanname="descr">Select the algorithm
1507 for the Chroma Spatial Filter (default <constant>1D_HOR</constant>).
1508 Possible values are:</entry>
1509               </row>
1510               <row>
1511                 <entrytbl spanname="descr" cols="2">
1512                   <tbody valign="top">
1513                     <row>
1514                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1515                       <entry>No filter</entry>
1516                     </row>
1517                     <row>
1518                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1519                       <entry>One-dimensional horizontal</entry>
1520                     </row>
1521                   </tbody>
1522                 </entrytbl>
1523               </row>
1524               <row><entry></entry></row>
1525               <row id="v4l2-mpeg-cx2341x-video-temporal-filter-mode">
1526                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE</constant>&nbsp;</entry>
1527                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_temporal_filter_mode</entry>
1528               </row><row><entry spanname="descr">Sets the Temporal
1529 Filter mode (default <constant>MANUAL</constant>). Possible values
1530 are:</entry>
1531               </row>
1532               <row>
1533                 <entrytbl spanname="descr" cols="2">
1534                   <tbody valign="top">
1535                     <row>
1536                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1537                       <entry>Choose the filter manually</entry>
1538                     </row>
1539                     <row>
1540                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1541                       <entry>Choose the filter automatically</entry>
1542                     </row>
1543                   </tbody>
1544                 </entrytbl>
1545               </row>
1546               <row><entry></entry></row>
1547               <row>
1548                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER</constant>&nbsp;</entry>
1549                 <entry>integer&nbsp;(0-31)</entry>
1550               </row><row><entry spanname="descr">The setting for the
1551 Temporal Filter. 0 = off, 31 = maximum. (Default is 8 for full-scale
1552 capturing and 0 for scaled capturing.)</entry>
1553               </row>
1554               <row><entry></entry></row>
1555               <row id="v4l2-mpeg-cx2341x-video-median-filter-type">
1556                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE</constant>&nbsp;</entry>
1557                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_median_filter_type</entry>
1558               </row><row><entry spanname="descr">Median Filter Type
1559 (default <constant>OFF</constant>). Possible values are:</entry>
1560               </row>
1561               <row>
1562                 <entrytbl spanname="descr" cols="2">
1563                   <tbody valign="top">
1564                     <row>
1565                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1566                       <entry>No filter</entry>
1567                     </row>
1568                     <row>
1569                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR</constant>&nbsp;</entry>
1570                       <entry>Horizontal filter</entry>
1571                     </row>
1572                     <row>
1573                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_VERT</constant>&nbsp;</entry>
1574                       <entry>Vertical filter</entry>
1575                     </row>
1576                     <row>
1577                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR_VERT</constant>&nbsp;</entry>
1578                       <entry>Horizontal and vertical filter</entry>
1579                     </row>
1580                     <row>
1581                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_DIAG</constant>&nbsp;</entry>
1582                       <entry>Diagonal filter</entry>
1583                     </row>
1584                   </tbody>
1585                 </entrytbl>
1586               </row>
1587               <row><entry></entry></row>
1588               <row>
1589                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1590                 <entry>integer&nbsp;(0-255)</entry>
1591               </row><row><entry spanname="descr">Threshold above which
1592 the luminance median filter is enabled (default 0)</entry>
1593               </row>
1594               <row><entry></entry></row>
1595               <row>
1596                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1597                 <entry>integer&nbsp;(0-255)</entry>
1598               </row><row><entry spanname="descr">Threshold below which
1599 the luminance median filter is enabled (default 255)</entry>
1600               </row>
1601               <row><entry></entry></row>
1602               <row>
1603                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1604                 <entry>integer&nbsp;(0-255)</entry>
1605               </row><row><entry spanname="descr">Threshold above which
1606 the chroma median filter is enabled (default 0)</entry>
1607               </row>
1608               <row><entry></entry></row>
1609               <row>
1610                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1611                 <entry>integer&nbsp;(0-255)</entry>
1612               </row><row><entry spanname="descr">Threshold below which
1613 the chroma median filter is enabled (default 255)</entry>
1614               </row>
1615               <row><entry></entry></row>
1616               <row>
1617                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_STREAM_INSERT_NAV_PACKETS</constant>&nbsp;</entry>
1618                 <entry>boolean</entry>
1619               </row>
1620               <row><entry spanname="descr">The CX2341X MPEG encoder
1621 can insert one empty MPEG-2 PES packet into the stream between every
1622 four video frames. The packet size is 2048 bytes, including the
1623 packet_start_code_prefix and stream_id fields. The stream_id is 0xBF
1624 (private stream 2). The payload consists of 0x00 bytes, to be filled
1625 in by the application. 0 = do not insert, 1 = insert packets.</entry>
1626               </row>
1627             </tbody>
1628           </tgroup>
1629         </table>
1630       </section>
1631     </section>
1632
1633     <section id="camera-controls">
1634       <title>Camera Control Reference</title>
1635
1636       <para>The Camera class includes controls for mechanical (or
1637 equivalent digital) features of a device such as controllable lenses
1638 or sensors.</para>
1639
1640     <table pgwide="1" frame="none" id="camera-control-id">
1641       <title>Camera Control IDs</title>
1642       <tgroup cols="4">
1643         <colspec colname="c1" colwidth="1*" />
1644         <colspec colname="c2" colwidth="6*" />
1645         <colspec colname="c3" colwidth="2*" />
1646         <colspec colname="c4" colwidth="6*" />
1647         <spanspec namest="c1" nameend="c2" spanname="id" />
1648         <spanspec namest="c2" nameend="c4" spanname="descr" />
1649         <thead>
1650           <row>
1651             <entry spanname="id" align="left">ID</entry>
1652             <entry align="left">Type</entry>
1653           </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1654           </row>
1655         </thead>
1656         <tbody valign="top">
1657           <row><entry></entry></row>
1658           <row>
1659             <entry spanname="id"><constant>V4L2_CID_CAMERA_CLASS</constant>&nbsp;</entry>
1660             <entry>class</entry>
1661           </row><row><entry spanname="descr">The Camera class
1662 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1663 description of this control class.</entry>
1664           </row>
1665           <row><entry></entry></row>
1666
1667           <row id="v4l2-exposure-auto-type">
1668             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO</constant>&nbsp;</entry>
1669             <entry>enum&nbsp;v4l2_exposure_auto_type</entry>
1670           </row><row><entry spanname="descr">Enables automatic
1671 adjustments of the exposure time and/or iris aperture. The effect of
1672 manual changes of the exposure time or iris aperture while these
1673 features are enabled is undefined, drivers should ignore such
1674 requests. Possible values are:</entry>
1675           </row>
1676           <row>
1677             <entrytbl spanname="descr" cols="2">
1678               <tbody valign="top">
1679                 <row>
1680                   <entry><constant>V4L2_EXPOSURE_AUTO</constant>&nbsp;</entry>
1681                       <entry>Automatic exposure time, automatic iris
1682 aperture.</entry>
1683                 </row>
1684                 <row>
1685                   <entry><constant>V4L2_EXPOSURE_MANUAL</constant>&nbsp;</entry>
1686                   <entry>Manual exposure time, manual iris.</entry>
1687                 </row>
1688                 <row>
1689                   <entry><constant>V4L2_EXPOSURE_SHUTTER_PRIORITY</constant>&nbsp;</entry>
1690                   <entry>Manual exposure time, auto iris.</entry>
1691                 </row>
1692                 <row>
1693                   <entry><constant>V4L2_EXPOSURE_APERTURE_PRIORITY</constant>&nbsp;</entry>
1694                   <entry>Auto exposure time, manual iris.</entry>
1695                 </row>
1696               </tbody>
1697             </entrytbl>
1698           </row>
1699           <row><entry></entry></row>
1700
1701           <row>
1702             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>&nbsp;</entry>
1703             <entry>integer</entry>
1704           </row><row><entry spanname="descr">Determines the exposure
1705 time of the camera sensor. The exposure time is limited by the frame
1706 interval. Drivers should interpret the values as 100 &micro;s units,
1707 where the value 1 stands for 1/10000th of a second, 10000 for 1 second
1708 and 100000 for 10 seconds.</entry>
1709           </row>
1710           <row><entry></entry></row>
1711
1712           <row>
1713             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>&nbsp;</entry>
1714             <entry>boolean</entry>
1715           </row><row><entry spanname="descr">When
1716 <constant>V4L2_CID_EXPOSURE_AUTO</constant> is set to
1717 <constant>AUTO</constant> or <constant>APERTURE_PRIORITY</constant>,
1718 this control determines if the device may dynamically vary the frame
1719 rate. By default this feature is disabled (0) and the frame rate must
1720 remain constant.</entry>
1721           </row>
1722           <row><entry></entry></row>
1723
1724           <row>
1725             <entry spanname="id"><constant>V4L2_CID_PAN_RELATIVE</constant>&nbsp;</entry>
1726             <entry>integer</entry>
1727           </row><row><entry spanname="descr">This control turns the
1728 camera horizontally by the specified amount. The unit is undefined. A
1729 positive value moves the camera to the right (clockwise when viewed
1730 from above), a negative value to the left. A value of zero does not
1731 cause motion. This is a write-only control.</entry>
1732           </row>
1733           <row><entry></entry></row>
1734
1735           <row>
1736             <entry spanname="id"><constant>V4L2_CID_TILT_RELATIVE</constant>&nbsp;</entry>
1737             <entry>integer</entry>
1738           </row><row><entry spanname="descr">This control turns the
1739 camera vertically by the specified amount. The unit is undefined. A
1740 positive value moves the camera up, a negative value down. A value of
1741 zero does not cause motion. This is a write-only control.</entry>
1742           </row>
1743           <row><entry></entry></row>
1744
1745           <row>
1746             <entry spanname="id"><constant>V4L2_CID_PAN_RESET</constant>&nbsp;</entry>
1747             <entry>button</entry>
1748           </row><row><entry spanname="descr">When this control is set,
1749 the camera moves horizontally to the default position.</entry>
1750           </row>
1751           <row><entry></entry></row>
1752
1753           <row>
1754             <entry spanname="id"><constant>V4L2_CID_TILT_RESET</constant>&nbsp;</entry>
1755             <entry>button</entry>
1756           </row><row><entry spanname="descr">When this control is set,
1757 the camera moves vertically to the default position.</entry>
1758           </row>
1759           <row><entry></entry></row>
1760
1761           <row>
1762             <entry spanname="id"><constant>V4L2_CID_PAN_ABSOLUTE</constant>&nbsp;</entry>
1763             <entry>integer</entry>
1764           </row><row><entry spanname="descr">This control
1765 turns the camera horizontally to the specified position. Positive
1766 values move the camera to the right (clockwise when viewed from above),
1767 negative values to the left. Drivers should interpret the values as arc
1768 seconds, with valid values between -180 * 3600 and +180 * 3600
1769 inclusive.</entry>
1770           </row>
1771           <row><entry></entry></row>
1772
1773           <row>
1774             <entry spanname="id"><constant>V4L2_CID_TILT_ABSOLUTE</constant>&nbsp;</entry>
1775             <entry>integer</entry>
1776           </row><row><entry spanname="descr">This control
1777 turns the camera vertically to the specified position. Positive values
1778 move the camera up, negative values down. Drivers should interpret the
1779 values as arc seconds, with valid values between -180 * 3600 and +180
1780 * 3600 inclusive.</entry>
1781           </row>
1782           <row><entry></entry></row>
1783
1784           <row>
1785             <entry spanname="id"><constant>V4L2_CID_FOCUS_ABSOLUTE</constant>&nbsp;</entry>
1786             <entry>integer</entry>
1787           </row><row><entry spanname="descr">This control sets the
1788 focal point of the camera to the specified position. The unit is
1789 undefined. Positive values set the focus closer to the camera,
1790 negative values towards infinity.</entry>
1791           </row>
1792           <row><entry></entry></row>
1793
1794           <row>
1795             <entry spanname="id"><constant>V4L2_CID_FOCUS_RELATIVE</constant>&nbsp;</entry>
1796             <entry>integer</entry>
1797           </row><row><entry spanname="descr">This control moves the
1798 focal point of the camera by the specified amount. The unit is
1799 undefined. Positive values move the focus closer to the camera,
1800 negative values towards infinity. This is a write-only control.</entry>
1801           </row>
1802           <row><entry></entry></row>
1803
1804           <row>
1805             <entry spanname="id"><constant>V4L2_CID_FOCUS_AUTO</constant>&nbsp;</entry>
1806             <entry>boolean</entry>
1807           </row><row><entry spanname="descr">Enables automatic focus
1808 adjustments. The effect of manual focus adjustments while this feature
1809 is enabled is undefined, drivers should ignore such requests.</entry>
1810           </row>
1811           <row><entry></entry></row>
1812
1813           <row>
1814             <entry spanname="id"><constant>V4L2_CID_ZOOM_ABSOLUTE</constant>&nbsp;</entry>
1815             <entry>integer</entry>
1816           </row><row><entry spanname="descr">Specify the objective lens
1817 focal length as an absolute value. The zoom unit is driver-specific and its
1818 value should be a positive integer.</entry>
1819           </row>
1820           <row><entry></entry></row>
1821
1822           <row>
1823             <entry spanname="id"><constant>V4L2_CID_ZOOM_RELATIVE</constant>&nbsp;</entry>
1824             <entry>integer</entry>
1825           </row><row><entry spanname="descr">Specify the objective lens
1826 focal length relatively to the current value. Positive values move the zoom
1827 lens group towards the telephoto direction, negative values towards the
1828 wide-angle direction. The zoom unit is driver-specific. This is a write-only control.</entry>
1829           </row>
1830           <row><entry></entry></row>
1831
1832           <row>
1833             <entry spanname="id"><constant>V4L2_CID_ZOOM_CONTINUOUS</constant>&nbsp;</entry>
1834             <entry>integer</entry>
1835           </row><row><entry spanname="descr">Move the objective lens group
1836 at the specified speed until it reaches physical device limits or until an
1837 explicit request to stop the movement. A positive value moves the zoom lens
1838 group towards the telephoto direction. A value of zero stops the zoom lens
1839 group movement. A negative value moves the zoom lens group towards the
1840 wide-angle direction. The zoom speed unit is driver-specific.</entry>
1841           </row>
1842           <row><entry></entry></row>
1843
1844           <row>
1845             <entry spanname="id"><constant>V4L2_CID_IRIS_ABSOLUTE</constant>&nbsp;</entry>
1846             <entry>integer</entry>
1847           </row><row><entry spanname="descr">This control sets the
1848 camera's aperture to the specified value. The unit is undefined.
1849 Larger values open the iris wider, smaller values close it.</entry>
1850           </row>
1851           <row><entry></entry></row>
1852
1853           <row>
1854             <entry spanname="id"><constant>V4L2_CID_IRIS_RELATIVE</constant>&nbsp;</entry>
1855             <entry>integer</entry>
1856           </row><row><entry spanname="descr">This control modifies the
1857 camera's aperture by the specified amount. The unit is undefined.
1858 Positive values open the iris one step further, negative values close
1859 it one step further. This is a write-only control.</entry>
1860           </row>
1861           <row><entry></entry></row>
1862
1863           <row>
1864             <entry spanname="id"><constant>V4L2_CID_PRIVACY</constant>&nbsp;</entry>
1865             <entry>boolean</entry>
1866           </row><row><entry spanname="descr">Prevent video from being acquired
1867 by the camera. When this control is set to <constant>TRUE</constant> (1), no
1868 image can be captured by the camera. Common means to enforce privacy are
1869 mechanical obturation of the sensor and firmware image processing, but the
1870 device is not restricted to these methods. Devices that implement the privacy
1871 control must support read access and may support write access.</entry>
1872           </row>
1873
1874           <row>
1875             <entry spanname="id"><constant>V4L2_CID_BAND_STOP_FILTER</constant>&nbsp;</entry>
1876             <entry>integer</entry>
1877           </row><row><entry spanname="descr">Switch the band-stop filter of a
1878 camera sensor on or off, or specify its strength. Such band-stop filters can
1879 be used, for example, to filter out the fluorescent light component.</entry>
1880           </row>
1881           <row><entry></entry></row>
1882         </tbody>
1883       </tgroup>
1884     </table>
1885   </section>
1886
1887     <section id="fm-tx-controls">
1888       <title>FM Transmitter Control Reference</title>
1889
1890       <para>The FM Transmitter (FM_TX) class includes controls for common features of
1891 FM transmissions capable devices. Currently this class includes parameters for audio
1892 compression, pilot tone generation, audio deviation limiter, RDS transmission and
1893 tuning power features.</para>
1894
1895       <table pgwide="1" frame="none" id="fm-tx-control-id">
1896       <title>FM_TX Control IDs</title>
1897
1898       <tgroup cols="4">
1899         <colspec colname="c1" colwidth="1*" />
1900         <colspec colname="c2" colwidth="6*" />
1901         <colspec colname="c3" colwidth="2*" />
1902         <colspec colname="c4" colwidth="6*" />
1903         <spanspec namest="c1" nameend="c2" spanname="id" />
1904         <spanspec namest="c2" nameend="c4" spanname="descr" />
1905         <thead>
1906           <row>
1907             <entry spanname="id" align="left">ID</entry>
1908             <entry align="left">Type</entry>
1909           </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1910           </row>
1911         </thead>
1912         <tbody valign="top">
1913           <row><entry></entry></row>
1914           <row>
1915             <entry spanname="id"><constant>V4L2_CID_FM_TX_CLASS</constant>&nbsp;</entry>
1916             <entry>class</entry>
1917           </row><row><entry spanname="descr">The FM_TX class
1918 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1919 description of this control class.</entry>
1920           </row>
1921           <row>
1922             <entry spanname="id"><constant>V4L2_CID_RDS_TX_DEVIATION</constant>&nbsp;</entry>
1923             <entry>integer</entry>
1924           </row>
1925           <row><entry spanname="descr">Configures RDS signal frequency deviation level in Hz.
1926 The range and step are driver-specific.</entry>
1927           </row>
1928           <row>
1929             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PI</constant>&nbsp;</entry>
1930             <entry>integer</entry>
1931           </row>
1932           <row><entry spanname="descr">Sets the RDS Programme Identification field
1933 for transmission.</entry>
1934           </row>
1935           <row>
1936             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PTY</constant>&nbsp;</entry>
1937             <entry>integer</entry>
1938           </row>
1939           <row><entry spanname="descr">Sets the RDS Programme Type field for transmission.
1940 This encodes up to 31 pre-defined programme types.</entry>
1941           </row>
1942           <row>
1943             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PS_NAME</constant>&nbsp;</entry>
1944             <entry>string</entry>
1945           </row>
1946           <row><entry spanname="descr">Sets the Programme Service name (PS_NAME) for transmission.
1947 It is intended for static display on a receiver. It is the primary aid to listeners in programme service
1948 identification and selection.  In Annex E of <xref linkend="en50067" />, the RDS specification,
1949 there is a full description of the correct character encoding for Programme Service name strings.
1950 Also from RDS specification, PS is usually a single eight character text. However, it is also possible
1951 to find receivers which can scroll strings sized as 8 x N characters. So, this control must be configured
1952 with steps of 8 characters. The result is it must always contain a string with size multiple of 8.</entry>
1953           </row>
1954           <row>
1955             <entry spanname="id"><constant>V4L2_CID_RDS_TX_RADIO_TEXT</constant>&nbsp;</entry>
1956             <entry>string</entry>
1957           </row>
1958           <row><entry spanname="descr">Sets the Radio Text info for transmission. It is a textual description of
1959 what is being broadcasted. RDS Radio Text can be applied when broadcaster wishes to transmit longer PS names,
1960 programme-related information or any other text. In these cases, RadioText should be used in addition to
1961 <constant>V4L2_CID_RDS_TX_PS_NAME</constant>. The encoding for Radio Text strings is also fully described
1962 in Annex E of <xref linkend="en50067" />. The length of Radio Text strings depends on which RDS Block is being
1963 used to transmit it, either 32 (2A block) or 64 (2B block).  However, it is also possible
1964 to find receivers which can scroll strings sized as 32 x N or 64 x N characters. So, this control must be configured
1965 with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. </entry>
1966           </row>
1967           <row>
1968             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_ENABLED</constant>&nbsp;</entry>
1969             <entry>boolean</entry>
1970           </row>
1971           <row><entry spanname="descr">Enables or disables the audio deviation limiter feature.
1972 The limiter is useful when trying to maximize the audio volume, minimize receiver-generated
1973 distortion and prevent overmodulation.
1974 </entry>
1975           </row>
1976           <row>
1977             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_RELEASE_TIME</constant>&nbsp;</entry>
1978             <entry>integer</entry>
1979           </row>
1980           <row><entry spanname="descr">Sets the audio deviation limiter feature release time.
1981 Unit is in useconds. Step and range are driver-specific.</entry>
1982           </row>
1983           <row>
1984             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_DEVIATION</constant>&nbsp;</entry>
1985             <entry>integer</entry>
1986           </row>
1987           <row><entry spanname="descr">Configures audio frequency deviation level in Hz.
1988 The range and step are driver-specific.</entry>
1989           </row>
1990           <row>
1991             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ENABLED</constant>&nbsp;</entry>
1992             <entry>boolean</entry>
1993           </row>
1994           <row><entry spanname="descr">Enables or disables the audio compression feature.
1995 This feature amplifies signals below the threshold by a fixed gain and compresses audio
1996 signals above the threshold by the ratio of Threshold/(Gain + Threshold).</entry>
1997           </row>
1998           <row>
1999             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_GAIN</constant>&nbsp;</entry>
2000             <entry>integer</entry>
2001           </row>
2002           <row><entry spanname="descr">Sets the gain for audio compression feature. It is
2003 a dB value. The range and step are driver-specific.</entry>
2004           </row>
2005           <row>
2006             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_THRESHOLD</constant>&nbsp;</entry>
2007             <entry>integer</entry>
2008           </row>
2009           <row><entry spanname="descr">Sets the threshold level for audio compression freature.
2010 It is a dB value. The range and step are driver-specific.</entry>
2011           </row>
2012           <row>
2013             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME</constant>&nbsp;</entry>
2014             <entry>integer</entry>
2015           </row>
2016           <row><entry spanname="descr">Sets the attack time for audio compression feature.
2017 It is a useconds value. The range and step are driver-specific.</entry>
2018           </row>
2019           <row>
2020             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME</constant>&nbsp;</entry>
2021             <entry>integer</entry>
2022           </row>
2023           <row><entry spanname="descr">Sets the release time for audio compression feature.
2024 It is a useconds value. The range and step are driver-specific.</entry>
2025           </row>
2026           <row>
2027             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_ENABLED</constant>&nbsp;</entry>
2028             <entry>boolean</entry>
2029           </row>
2030           <row><entry spanname="descr">Enables or disables the pilot tone generation feature.</entry>
2031           </row>
2032           <row>
2033             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_DEVIATION</constant>&nbsp;</entry>
2034             <entry>integer</entry>
2035           </row>
2036           <row><entry spanname="descr">Configures pilot tone frequency deviation level. Unit is
2037 in Hz. The range and step are driver-specific.</entry>
2038           </row>
2039           <row>
2040             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_FREQUENCY</constant>&nbsp;</entry>
2041             <entry>integer</entry>
2042           </row>
2043           <row><entry spanname="descr">Configures pilot tone frequency value. Unit is
2044 in Hz. The range and step are driver-specific.</entry>
2045           </row>
2046           <row>
2047             <entry spanname="id"><constant>V4L2_CID_TUNE_PREEMPHASIS</constant>&nbsp;</entry>
2048             <entry>integer</entry>
2049           </row>
2050           <row id="v4l2-preemphasis"><entry spanname="descr">Configures the pre-emphasis value for broadcasting.
2051 A pre-emphasis filter is applied to the broadcast to accentuate the high audio frequencies.
2052 Depending on the region, a time constant of either 50 or 75 useconds is used. The enum&nbsp;v4l2_preemphasis
2053 defines possible values for pre-emphasis. Here they are:</entry>
2054         </row><row>
2055         <entrytbl spanname="descr" cols="2">
2056                   <tbody valign="top">
2057                     <row>
2058                       <entry><constant>V4L2_PREEMPHASIS_DISABLED</constant>&nbsp;</entry>
2059                       <entry>No pre-emphasis is applied.</entry>
2060                     </row>
2061                     <row>
2062                       <entry><constant>V4L2_PREEMPHASIS_50_uS</constant>&nbsp;</entry>
2063                       <entry>A pre-emphasis of 50 uS is used.</entry>
2064                     </row>
2065                     <row>
2066                       <entry><constant>V4L2_PREEMPHASIS_75_uS</constant>&nbsp;</entry>
2067                       <entry>A pre-emphasis of 75 uS is used.</entry>
2068                     </row>
2069                   </tbody>
2070                 </entrytbl>
2071
2072           </row>
2073           <row>
2074             <entry spanname="id"><constant>V4L2_CID_TUNE_POWER_LEVEL</constant>&nbsp;</entry>
2075             <entry>integer</entry>
2076           </row>
2077           <row><entry spanname="descr">Sets the output power level for signal transmission.
2078 Unit is in dBuV. Range and step are driver-specific.</entry>
2079           </row>
2080           <row>
2081             <entry spanname="id"><constant>V4L2_CID_TUNE_ANTENNA_CAPACITOR</constant>&nbsp;</entry>
2082             <entry>integer</entry>
2083           </row>
2084           <row><entry spanname="descr">This selects the value of antenna tuning capacitor
2085 manually or automatically if set to zero. Unit, range and step are driver-specific.</entry>
2086           </row>
2087           <row><entry></entry></row>
2088         </tbody>
2089       </tgroup>
2090       </table>
2091
2092 <para>For more details about RDS specification, refer to
2093 <xref linkend="en50067" /> document, from CENELEC.</para>
2094     </section>
2095 </section>
2096
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