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_LASTP1</constant></entry>
 316             <entry></entry>
 317             <entry>End of the predefined control IDs (currently
 318 <constant>V4L2_CID_BG_COLOR</constant> + 1).</entry>
 319           </row>
 320           <row>
 321             <entry><constant>V4L2_CID_PRIVATE_BASE</constant></entry>
 322             <entry></entry>
 323             <entry>ID of the first custom (driver specific) control.
 324 Applications depending on particular custom controls should check the
 325 driver name and version, see <xref linkend="querycap" />.</entry>
 326           </row>
 327         </tbody>
 328       </tgroup>
 329     </table>
 330
 331     <para>Applications can enumerate the available controls with the
 332 &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls, get and set a
 333 control value with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls.
 334 Drivers must implement <constant>VIDIOC_QUERYCTRL</constant>,
 335 <constant>VIDIOC_G_CTRL</constant> and
 336 <constant>VIDIOC_S_CTRL</constant> when the device has one or more
 337 controls, <constant>VIDIOC_QUERYMENU</constant> when it has one or
 338 more menu type controls.</para>
 339
 340     <example>
 341       <title>Enumerating all controls</title>
 342
 343       <programlisting>
 344 &v4l2-queryctrl; queryctrl;
 345 &v4l2-querymenu; querymenu;
 346
 347 static void
 348 enumerate_menu (void)
 349 {
 350         printf ("  Menu items:\n");
 351
 352         memset (&amp;querymenu, 0, sizeof (querymenu));
 353         querymenu.id = queryctrl.id;
 354
 355         for (querymenu.index = queryctrl.minimum;
 356              querymenu.index &lt;= queryctrl.maximum;
 357               querymenu.index++) {
 358                 if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &amp;querymenu)) {
 359                         printf ("  %s\n", querymenu.name);
 360                 } else {
 361                         perror ("VIDIOC_QUERYMENU");
 362                         exit (EXIT_FAILURE);
 363                 }
 364         }
 365 }
 366
 367 memset (&amp;queryctrl, 0, sizeof (queryctrl));
 368
 369 for (queryctrl.id = V4L2_CID_BASE;
 370      queryctrl.id &lt; V4L2_CID_LASTP1;
 371      queryctrl.id++) {
 372         if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 373                 if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
 374                         continue;
 375
 376                 printf ("Control %s\n", queryctrl.name);
 377
 378                 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
 379                         enumerate_menu ();
 380         } else {
 381                 if (errno == EINVAL)
 382                         continue;
 383
 384                 perror ("VIDIOC_QUERYCTRL");
 385                 exit (EXIT_FAILURE);
 386         }
 387 }
 388
 389 for (queryctrl.id = V4L2_CID_PRIVATE_BASE;;
 390      queryctrl.id++) {
 391         if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 392                 if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
 393                         continue;
 394
 395                 printf ("Control %s\n", queryctrl.name);
 396
 397                 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
 398                         enumerate_menu ();
 399         } else {
 400                 if (errno == EINVAL)
 401                         break;
 402
 403                 perror ("VIDIOC_QUERYCTRL");
 404                 exit (EXIT_FAILURE);
 405         }
 406 }
 407 </programlisting>
 408     </example>
 409
 410     <example>
 411       <title>Changing controls</title>
 412
 413       <programlisting>
 414 &v4l2-queryctrl; queryctrl;
 415 &v4l2-control; control;
 416
 417 memset (&amp;queryctrl, 0, sizeof (queryctrl));
 418 queryctrl.id = V4L2_CID_BRIGHTNESS;
 419
 420 if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 421         if (errno != EINVAL) {
 422                 perror ("VIDIOC_QUERYCTRL");
 423                 exit (EXIT_FAILURE);
 424         } else {
 425                 printf ("V4L2_CID_BRIGHTNESS is not supported\n");
 426         }
 427 } else if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED) {
 428         printf ("V4L2_CID_BRIGHTNESS is not supported\n");
 429 } else {
 430         memset (&amp;control, 0, sizeof (control));
 431         control.id = V4L2_CID_BRIGHTNESS;
 432         control.value = queryctrl.default_value;
 433
 434         if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)) {
 435                 perror ("VIDIOC_S_CTRL");
 436                 exit (EXIT_FAILURE);
 437         }
 438 }
 439
 440 memset (&amp;control, 0, sizeof (control));
 441 control.id = V4L2_CID_CONTRAST;
 442
 443 if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &amp;control)) {
 444         control.value += 1;
 445
 446         /* The driver may clamp the value or return ERANGE, ignored here */
 447
 448         if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)
 449             &amp;&amp; errno != ERANGE) {
 450                 perror ("VIDIOC_S_CTRL");
 451                 exit (EXIT_FAILURE);
 452         }
 453 /* Ignore if V4L2_CID_CONTRAST is unsupported */
 454 } else if (errno != EINVAL) {
 455         perror ("VIDIOC_G_CTRL");
 456         exit (EXIT_FAILURE);
 457 }
 458
 459 control.id = V4L2_CID_AUDIO_MUTE;
 460 control.value = TRUE; /* silence */
 461
 462 /* Errors ignored */
 463 ioctl (fd, VIDIOC_S_CTRL, &amp;control);
 464 </programlisting>
 465     </example>
 466   </section>
 467
 468   <section id="extended-controls">
 469     <title>Extended Controls</title>
 470
 471     <section>
 472       <title>Introduction</title>
 473
 474       <para>The control mechanism as originally designed was meant
 475 to be used for user settings (brightness, saturation, etc). However,
 476 it turned out to be a very useful model for implementing more
 477 complicated driver APIs where each driver implements only a subset of
 478 a larger API.</para>
 479
 480       <para>The MPEG encoding API was the driving force behind
 481 designing and implementing this extended control mechanism: the MPEG
 482 standard is quite large and the currently supported hardware MPEG
 483 encoders each only implement a subset of this standard. Further more,
 484 many parameters relating to how the video is encoded into an MPEG
 485 stream are specific to the MPEG encoding chip since the MPEG standard
 486 only defines the format of the resulting MPEG stream, not how the
 487 video is actually encoded into that format.</para>
 488
 489       <para>Unfortunately, the original control API lacked some
 490 features needed for these new uses and so it was extended into the
 491 (not terribly originally named) extended control API.</para>
 492
 493       <para>Even though the MPEG encoding API was the first effort
 494 to use the Extended Control API, nowadays there are also other classes
 495 of Extended Controls, such as Camera Controls and FM Transmitter Controls.
 496 The Extended Controls API as well as all Extended Controls classes are
 497 described in the following text.</para>
 498     </section>
 499
 500     <section>
 501       <title>The Extended Control API</title>
 502
 503       <para>Three new ioctls are available: &VIDIOC-G-EXT-CTRLS;,
 504 &VIDIOC-S-EXT-CTRLS; and &VIDIOC-TRY-EXT-CTRLS;. These ioctls act on
 505 arrays of controls (as opposed to the &VIDIOC-G-CTRL; and
 506 &VIDIOC-S-CTRL; ioctls that act on a single control). This is needed
 507 since it is often required to atomically change several controls at
 508 once.</para>
 509
 510       <para>Each of the new ioctls expects a pointer to a
 511 &v4l2-ext-controls;. This structure contains a pointer to the control
 512 array, a count of the number of controls in that array and a control
 513 class. Control classes are used to group similar controls into a
 514 single class. For example, control class
 515 <constant>V4L2_CTRL_CLASS_USER</constant> contains all user controls
 516 (&ie; all controls that can also be set using the old
 517 <constant>VIDIOC_S_CTRL</constant> ioctl). Control class
 518 <constant>V4L2_CTRL_CLASS_MPEG</constant> contains all controls
 519 relating to MPEG encoding, etc.</para>
 520
 521       <para>All controls in the control array must belong to the
 522 specified control class. An error is returned if this is not the
 523 case.</para>
 524
 525       <para>It is also possible to use an empty control array (count
 526 == 0) to check whether the specified control class is
 527 supported.</para>
 528
 529       <para>The control array is a &v4l2-ext-control; array. The
 530 <structname>v4l2_ext_control</structname> structure is very similar to
 531 &v4l2-control;, except for the fact that it also allows for 64-bit
 532 values and pointers to be passed.</para>
 533
 534       <para>It is important to realize that due to the flexibility of
 535 controls it is necessary to check whether the control you want to set
 536 actually is supported in the driver and what the valid range of values
 537 is. So use the &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls to
 538 check this. Also note that it is possible that some of the menu
 539 indices in a control of type <constant>V4L2_CTRL_TYPE_MENU</constant>
 540 may not be supported (<constant>VIDIOC_QUERYMENU</constant> will
 541 return an error). A good example is the list of supported MPEG audio
 542 bitrates. Some drivers only support one or two bitrates, others
 543 support a wider range.</para>
 544     </section>
 545
 546     <section>
 547       <title>Enumerating Extended Controls</title>
 548
 549       <para>The recommended way to enumerate over the extended
 550 controls is by using &VIDIOC-QUERYCTRL; in combination with the
 551 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag:</para>
 552
 553       <informalexample>
 554         <programlisting>
 555 &v4l2-queryctrl; qctrl;
 556
 557 qctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
 558 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
 559         /* ... */
 560         qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
 561 }
 562 </programlisting>
 563       </informalexample>
 564
 565       <para>The initial control ID is set to 0 ORed with the
 566 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag. The
 567 <constant>VIDIOC_QUERYCTRL</constant> ioctl will return the first
 568 control with a higher ID than the specified one. When no such controls
 569 are found an error is returned.</para>
 570
 571       <para>If you want to get all controls within a specific control
 572 class, then you can set the initial
 573 <structfield>qctrl.id</structfield> value to the control class and add
 574 an extra check to break out of the loop when a control of another
 575 control class is found:</para>
 576
 577       <informalexample>
 578         <programlisting>
 579 qctrl.id = V4L2_CTRL_CLASS_MPEG | V4L2_CTRL_FLAG_NEXT_CTRL;
 580 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
 581         if (V4L2_CTRL_ID2CLASS (qctrl.id) != V4L2_CTRL_CLASS_MPEG)
 582                 break;
 583                 /* ... */
 584                 qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
 585         }
 586 </programlisting>
 587       </informalexample>
 588
 589       <para>The 32-bit <structfield>qctrl.id</structfield> value is
 590 subdivided into three bit ranges: the top 4 bits are reserved for
 591 flags (&eg; <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>) and are not
 592 actually part of the ID. The remaining 28 bits form the control ID, of
 593 which the most significant 12 bits define the control class and the
 594 least significant 16 bits identify the control within the control
 595 class. It is guaranteed that these last 16 bits are always non-zero
 596 for controls. The range of 0x1000 and up are reserved for
 597 driver-specific controls. The macro
 598 <constant>V4L2_CTRL_ID2CLASS(id)</constant> returns the control class
 599 ID based on a control ID.</para>
 600
 601       <para>If the driver does not support extended controls, then
 602 <constant>VIDIOC_QUERYCTRL</constant> will fail when used in
 603 combination with <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>. In
 604 that case the old method of enumerating control should be used (see
 605 1.8). But if it is supported, then it is guaranteed to enumerate over
 606 all controls, including driver-private controls.</para>
 607     </section>
 608
 609     <section>
 610       <title>Creating Control Panels</title>
 611
 612       <para>It is possible to create control panels for a graphical
 613 user interface where the user can select the various controls.
 614 Basically you will have to iterate over all controls using the method
 615 described above. Each control class starts with a control of type
 616 <constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant>.
 617 <constant>VIDIOC_QUERYCTRL</constant> will return the name of this
 618 control class which can be used as the title of a tab page within a
 619 control panel.</para>
 620
 621       <para>The flags field of &v4l2-queryctrl; also contains hints on
 622 the behavior of the control. See the &VIDIOC-QUERYCTRL; documentation
 623 for more details.</para>
 624     </section>
 625
 626     <section id="mpeg-controls">
 627       <title>MPEG Control Reference</title>
 628
 629       <para>Below all controls within the MPEG control class are
 630 described. First the generic controls, then controls specific for
 631 certain hardware.</para>
 632
 633       <section>
 634         <title>Generic MPEG Controls</title>
 635
 636         <table pgwide="1" frame="none" id="mpeg-control-id">
 637           <title>MPEG Control IDs</title>
 638           <tgroup cols="4">
 639             <colspec colname="c1" colwidth="1*" />
 640             <colspec colname="c2" colwidth="6*" />
 641             <colspec colname="c3" colwidth="2*" />
 642             <colspec colname="c4" colwidth="6*" />
 643             <spanspec namest="c1" nameend="c2" spanname="id" />
 644             <spanspec namest="c2" nameend="c4" spanname="descr" />
 645             <thead>
 646               <row>
 647                 <entry spanname="id" align="left">ID</entry>
 648                 <entry align="left">Type</entry>
 649               </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
 650               </row>
 651             </thead>
 652             <tbody valign="top">
 653               <row><entry></entry></row>
 654               <row>
 655                 <entry spanname="id"><constant>V4L2_CID_MPEG_CLASS</constant>&nbsp;</entry>
 656                 <entry>class</entry>
 657               </row><row><entry spanname="descr">The MPEG class
 658 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
 659 description of this control class. This description can be used as the
 660 caption of a Tab page in a GUI, for example.</entry>
 661               </row>
 662               <row><entry></entry></row>
 663               <row id="v4l2-mpeg-stream-type">
 664                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_TYPE</constant>&nbsp;</entry>
 665                 <entry>enum&nbsp;v4l2_mpeg_stream_type</entry>
 666               </row><row><entry spanname="descr">The MPEG-1, -2 or -4
 667 output stream type. One cannot assume anything here. Each hardware
 668 MPEG encoder tends to support different subsets of the available MPEG
 669 stream types. The currently defined stream types are:</entry>
 670               </row>
 671               <row>
 672                 <entrytbl spanname="descr" cols="2">
 673                   <tbody valign="top">
 674                     <row>
 675                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_PS</constant>&nbsp;</entry>
 676                       <entry>MPEG-2 program stream</entry>
 677                     </row>
 678                     <row>
 679                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_TS</constant>&nbsp;</entry>
 680                       <entry>MPEG-2 transport stream</entry>
 681                     </row>
 682                     <row>
 683                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_SS</constant>&nbsp;</entry>
 684                       <entry>MPEG-1 system stream</entry>
 685                     </row>
 686                     <row>
 687                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_DVD</constant>&nbsp;</entry>
 688                       <entry>MPEG-2 DVD-compatible stream</entry>
 689                     </row>
 690                     <row>
 691                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_VCD</constant>&nbsp;</entry>
 692                       <entry>MPEG-1 VCD-compatible stream</entry>
 693                     </row>
 694                     <row>
 695                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_SVCD</constant>&nbsp;</entry>
 696                       <entry>MPEG-2 SVCD-compatible stream</entry>
 697                     </row>
 698                   </tbody>
 699                 </entrytbl>
 700               </row>
 701               <row><entry></entry></row>
 702               <row>
 703                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PMT</constant>&nbsp;</entry>
 704                 <entry>integer</entry>
 705               </row><row><entry spanname="descr">Program Map Table
 706 Packet ID for the MPEG transport stream (default 16)</entry>
 707               </row>
 708               <row><entry></entry></row>
 709               <row>
 710                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_AUDIO</constant>&nbsp;</entry>
 711                 <entry>integer</entry>
 712               </row><row><entry spanname="descr">Audio Packet ID for
 713 the MPEG transport stream (default 256)</entry>
 714               </row>
 715               <row><entry></entry></row>
 716               <row>
 717                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_VIDEO</constant>&nbsp;</entry>
 718                 <entry>integer</entry>
 719               </row><row><entry spanname="descr">Video Packet ID for
 720 the MPEG transport stream (default 260)</entry>
 721               </row>
 722               <row><entry></entry></row>
 723               <row>
 724                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PCR</constant>&nbsp;</entry>
 725                 <entry>integer</entry>
 726               </row><row><entry spanname="descr">Packet ID for the
 727 MPEG transport stream carrying PCR fields (default 259)</entry>
 728               </row>
 729               <row><entry></entry></row>
 730               <row>
 731                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_AUDIO</constant>&nbsp;</entry>
 732                 <entry>integer</entry>
 733               </row><row><entry spanname="descr">Audio ID for MPEG
 734 PES</entry>
 735               </row>
 736               <row><entry></entry></row>
 737               <row>
 738                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_VIDEO</constant>&nbsp;</entry>
 739                 <entry>integer</entry>
 740               </row><row><entry spanname="descr">Video ID for MPEG
 741 PES</entry>
 742               </row>
 743               <row><entry></entry></row>
 744               <row id="v4l2-mpeg-stream-vbi-fmt">
 745                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_VBI_FMT</constant>&nbsp;</entry>
 746                 <entry>enum&nbsp;v4l2_mpeg_stream_vbi_fmt</entry>
 747               </row><row><entry spanname="descr">Some cards can embed
 748 VBI data (&eg; Closed Caption, Teletext) into the MPEG stream. This
 749 control selects whether VBI data should be embedded, and if so, what
 750 embedding method should be used. The list of possible VBI formats
 751 depends on the driver. The currently defined VBI format types
 752 are:</entry>
 753               </row>
 754               <row>
 755                 <entrytbl spanname="descr" cols="2">
 756                   <tbody valign="top">
 757                     <row>
 758                       <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_NONE</constant>&nbsp;</entry>
 759                       <entry>No VBI in the MPEG stream</entry>
 760                     </row>
 761                     <row>
 762                       <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant>&nbsp;</entry>
 763                       <entry>VBI in private packets, IVTV format (documented
 764 in the kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.vbi</filename>)</entry>
 765                     </row>
 766                   </tbody>
 767                 </entrytbl>
 768               </row>
 769               <row><entry></entry></row>
 770               <row id="v4l2-mpeg-audio-sampling-freq">
 771                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ</constant>&nbsp;</entry>
 772                 <entry>enum&nbsp;v4l2_mpeg_audio_sampling_freq</entry>
 773               </row><row><entry spanname="descr">MPEG Audio sampling
 774 frequency. Possible values are:</entry>
 775               </row>
 776               <row>
 777                 <entrytbl spanname="descr" cols="2">
 778                   <tbody valign="top">
 779                     <row>
 780                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_44100</constant>&nbsp;</entry>
 781                       <entry>44.1 kHz</entry>
 782                     </row>
 783                     <row>
 784                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_48000</constant>&nbsp;</entry>
 785                       <entry>48 kHz</entry>
 786                     </row>
 787                     <row>
 788                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_32000</constant>&nbsp;</entry>
 789                       <entry>32 kHz</entry>
 790                     </row>
 791                   </tbody>
 792                 </entrytbl>
 793               </row>
 794               <row><entry></entry></row>
 795               <row id="v4l2-mpeg-audio-encoding">
 796                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_ENCODING</constant>&nbsp;</entry>
 797                 <entry>enum&nbsp;v4l2_mpeg_audio_encoding</entry>
 798               </row><row><entry spanname="descr">MPEG Audio encoding.
 799 Possible values are:</entry>
 800               </row>
 801               <row>
 802                 <entrytbl spanname="descr" cols="2">
 803                   <tbody valign="top">
 804                     <row>
 805                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_1</constant>&nbsp;</entry>
 806                       <entry>MPEG-1/2 Layer I encoding</entry>
 807                     </row>
 808                     <row>
 809                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_2</constant>&nbsp;</entry>
 810                       <entry>MPEG-1/2 Layer II encoding</entry>
 811                     </row>
 812                     <row>
 813                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_3</constant>&nbsp;</entry>
 814                       <entry>MPEG-1/2 Layer III encoding</entry>
 815                     </row>
 816                     <row>
 817                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant>&nbsp;</entry>
 818                       <entry>MPEG-2/4 AAC (Advanced Audio Coding)</entry>
 819                     </row>
 820                     <row>
 821                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant>&nbsp;</entry>
 822                       <entry>AC-3 aka ATSC A/52 encoding</entry>
 823                     </row>
 824                   </tbody>
 825                 </entrytbl>
 826               </row>
 827               <row><entry></entry></row>
 828               <row id="v4l2-mpeg-audio-l1-bitrate">
 829                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L1_BITRATE</constant>&nbsp;</entry>
 830                 <entry>enum&nbsp;v4l2_mpeg_audio_l1_bitrate</entry>
 831               </row><row><entry spanname="descr">MPEG-1/2 Layer I bitrate.
 832 Possible values are:</entry>
 833               </row>
 834               <row>
 835                 <entrytbl spanname="descr" cols="2">
 836                   <tbody valign="top">
 837                     <row>
 838                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_32K</constant>&nbsp;</entry>
 839                       <entry>32 kbit/s</entry></row>
 840                     <row>
 841                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_64K</constant>&nbsp;</entry>
 842                       <entry>64 kbit/s</entry>
 843                     </row>
 844                     <row>
 845                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_96K</constant>&nbsp;</entry>
 846                       <entry>96 kbit/s</entry>
 847                     </row>
 848                     <row>
 849                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_128K</constant>&nbsp;</entry>
 850                       <entry>128 kbit/s</entry>
 851                     </row>
 852                     <row>
 853                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_160K</constant>&nbsp;</entry>
 854                       <entry>160 kbit/s</entry>
 855                     </row>
 856                     <row>
 857                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_192K</constant>&nbsp;</entry>
 858                       <entry>192 kbit/s</entry>
 859                     </row>
 860                     <row>
 861                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_224K</constant>&nbsp;</entry>
 862                       <entry>224 kbit/s</entry>
 863                     </row>
 864                     <row>
 865                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_256K</constant>&nbsp;</entry>
 866                       <entry>256 kbit/s</entry>
 867                     </row>
 868                     <row>
 869                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_288K</constant>&nbsp;</entry>
 870                       <entry>288 kbit/s</entry>
 871                     </row>
 872                     <row>
 873                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_320K</constant>&nbsp;</entry>
 874                       <entry>320 kbit/s</entry>
 875                     </row>
 876                     <row>
 877                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_352K</constant>&nbsp;</entry>
 878                       <entry>352 kbit/s</entry>
 879                     </row>
 880                     <row>
 881                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_384K</constant>&nbsp;</entry>
 882                       <entry>384 kbit/s</entry>
 883                     </row>
 884                     <row>
 885                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_416K</constant>&nbsp;</entry>
 886                       <entry>416 kbit/s</entry>
 887                     </row>
 888                     <row>
 889                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_448K</constant>&nbsp;</entry>
 890                       <entry>448 kbit/s</entry>
 891                     </row>
 892                   </tbody>
 893                 </entrytbl>
 894               </row>
 895               <row><entry></entry></row>
 896               <row id="v4l2-mpeg-audio-l2-bitrate">
 897                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L2_BITRATE</constant>&nbsp;</entry>
 898                 <entry>enum&nbsp;v4l2_mpeg_audio_l2_bitrate</entry>
 899               </row><row><entry spanname="descr">MPEG-1/2 Layer II bitrate.
 900 Possible values are:</entry>
 901               </row>
 902               <row>
 903                 <entrytbl spanname="descr" cols="2">
 904                   <tbody valign="top">
 905                     <row>
 906                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_32K</constant>&nbsp;</entry>
 907                       <entry>32 kbit/s</entry>
 908                     </row>
 909                     <row>
 910                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_48K</constant>&nbsp;</entry>
 911                       <entry>48 kbit/s</entry>
 912                     </row>
 913                     <row>
 914                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_56K</constant>&nbsp;</entry>
 915                       <entry>56 kbit/s</entry>
 916                     </row>
 917                     <row>
 918                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_64K</constant>&nbsp;</entry>
 919                       <entry>64 kbit/s</entry>
 920                     </row>
 921                     <row>
 922                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_80K</constant>&nbsp;</entry>
 923                       <entry>80 kbit/s</entry>
 924                     </row>
 925                     <row>
 926                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_96K</constant>&nbsp;</entry>
 927                       <entry>96 kbit/s</entry>
 928                     </row>
 929                     <row>
 930                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_112K</constant>&nbsp;</entry>
 931                       <entry>112 kbit/s</entry>
 932                     </row>
 933                     <row>
 934                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_128K</constant>&nbsp;</entry>
 935                       <entry>128 kbit/s</entry>
 936                     </row>
 937                     <row>
 938                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_160K</constant>&nbsp;</entry>
 939                       <entry>160 kbit/s</entry>
 940                     </row>
 941                     <row>
 942                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_192K</constant>&nbsp;</entry>
 943                       <entry>192 kbit/s</entry>
 944                     </row>
 945                     <row>
 946                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_224K</constant>&nbsp;</entry>
 947                       <entry>224 kbit/s</entry>
 948                     </row>
 949                     <row>
 950                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_256K</constant>&nbsp;</entry>
 951                       <entry>256 kbit/s</entry>
 952                     </row>
 953                     <row>
 954                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_320K</constant>&nbsp;</entry>
 955                       <entry>320 kbit/s</entry>
 956                     </row>
 957                     <row>
 958                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_384K</constant>&nbsp;</entry>
 959                       <entry>384 kbit/s</entry>
 960                     </row>
 961                   </tbody>
 962                 </entrytbl>
 963               </row>
 964               <row><entry></entry></row>
 965               <row id="v4l2-mpeg-audio-l3-bitrate">
 966                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L3_BITRATE</constant>&nbsp;</entry>
 967                 <entry>enum&nbsp;v4l2_mpeg_audio_l3_bitrate</entry>
 968               </row><row><entry spanname="descr">MPEG-1/2 Layer III bitrate.
 969 Possible values are:</entry>
 970               </row>
 971               <row>
 972                 <entrytbl spanname="descr" cols="2">
 973                   <tbody valign="top">
 974                     <row>
 975                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_32K</constant>&nbsp;</entry>
 976                       <entry>32 kbit/s</entry>
 977                     </row>
 978                     <row>
 979                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_40K</constant>&nbsp;</entry>
 980                       <entry>40 kbit/s</entry>
 981                     </row>
 982                     <row>
 983                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_48K</constant>&nbsp;</entry>
 984                       <entry>48 kbit/s</entry>
 985                     </row>
 986                     <row>
 987                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_56K</constant>&nbsp;</entry>
 988                       <entry>56 kbit/s</entry>
 989                     </row>
 990                     <row>
 991                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_64K</constant>&nbsp;</entry>
 992                       <entry>64 kbit/s</entry>
 993                     </row>
 994                     <row>
 995                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_80K</constant>&nbsp;</entry>
 996                       <entry>80 kbit/s</entry>
 997                     </row>
 998                     <row>
 999                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_96K</constant>&nbsp;</entry>
1000                       <entry>96 kbit/s</entry>
1001                     </row>
1002                     <row>
1003                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_112K</constant>&nbsp;</entry>
1004                       <entry>112 kbit/s</entry>
1005                     </row>
1006                     <row>
1007                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_128K</constant>&nbsp;</entry>
1008                       <entry>128 kbit/s</entry>
1009                     </row>
1010                     <row>
1011                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_160K</constant>&nbsp;</entry>
1012                       <entry>160 kbit/s</entry>
1013                     </row>
1014                     <row>
1015                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_192K</constant>&nbsp;</entry>
1016                       <entry>192 kbit/s</entry>
1017                     </row>
1018                     <row>
1019                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_224K</constant>&nbsp;</entry>
1020                       <entry>224 kbit/s</entry>
1021                     </row>
1022                     <row>
1023                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_256K</constant>&nbsp;</entry>
1024                       <entry>256 kbit/s</entry>
1025                     </row>
1026                     <row>
1027                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_320K</constant>&nbsp;</entry>
1028                       <entry>320 kbit/s</entry>
1029                     </row>
1030                   </tbody>
1031                 </entrytbl>
1032               </row>
1033               <row><entry></entry></row>
1034               <row>
1035                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AAC_BITRATE</constant>&nbsp;</entry>
1036                 <entry>integer</entry>
1037               </row><row><entry spanname="descr">AAC bitrate in bits per second.</entry>
1038               </row>
1039               <row><entry></entry></row>
1040               <row id="v4l2-mpeg-audio-ac3-bitrate">
1041                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AC3_BITRATE</constant>&nbsp;</entry>
1042                 <entry>enum&nbsp;v4l2_mpeg_audio_ac3_bitrate</entry>
1043               </row><row><entry spanname="descr">AC-3 bitrate.
1044 Possible values are:</entry>
1045               </row>
1046               <row>
1047                 <entrytbl spanname="descr" cols="2">
1048                   <tbody valign="top">
1049                     <row>
1050                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_32K</constant>&nbsp;</entry>
1051                       <entry>32 kbit/s</entry>
1052                     </row>
1053                     <row>
1054                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_40K</constant>&nbsp;</entry>
1055                       <entry>40 kbit/s</entry>
1056                     </row>
1057                     <row>
1058                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_48K</constant>&nbsp;</entry>
1059                       <entry>48 kbit/s</entry>
1060                     </row>
1061                     <row>
1062                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_56K</constant>&nbsp;</entry>
1063                       <entry>56 kbit/s</entry>
1064                     </row>
1065                     <row>
1066                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_64K</constant>&nbsp;</entry>
1067                       <entry>64 kbit/s</entry>
1068                     </row>
1069                     <row>
1070                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_80K</constant>&nbsp;</entry>
1071                       <entry>80 kbit/s</entry>
1072                     </row>
1073                     <row>
1074                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_96K</constant>&nbsp;</entry>
1075                       <entry>96 kbit/s</entry>
1076                     </row>
1077                     <row>
1078                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_112K</constant>&nbsp;</entry>
1079                       <entry>112 kbit/s</entry>
1080                     </row>
1081                     <row>
1082                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_128K</constant>&nbsp;</entry>
1083                       <entry>128 kbit/s</entry>
1084                     </row>
1085                     <row>
1086                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_160K</constant>&nbsp;</entry>
1087                       <entry>160 kbit/s</entry>
1088                     </row>
1089                     <row>
1090                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_192K</constant>&nbsp;</entry>
1091                       <entry>192 kbit/s</entry>
1092                     </row>
1093                     <row>
1094                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_224K</constant>&nbsp;</entry>
1095                       <entry>224 kbit/s</entry>
1096                     </row>
1097                     <row>
1098                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_256K</constant>&nbsp;</entry>
1099                       <entry>256 kbit/s</entry>
1100                     </row>
1101                     <row>
1102                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_320K</constant>&nbsp;</entry>
1103                       <entry>320 kbit/s</entry>
1104                     </row>
1105                     <row>
1106                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_384K</constant>&nbsp;</entry>
1107                       <entry>384 kbit/s</entry>
1108                     </row>
1109                     <row>
1110                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_448K</constant>&nbsp;</entry>
1111                       <entry>448 kbit/s</entry>
1112                     </row>
1113                     <row>
1114                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_512K</constant>&nbsp;</entry>
1115                       <entry>512 kbit/s</entry>
1116                     </row>
1117                     <row>
1118                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_576K</constant>&nbsp;</entry>
1119                       <entry>576 kbit/s</entry>
1120                     </row>
1121                     <row>
1122                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_640K</constant>&nbsp;</entry>
1123                       <entry>640 kbit/s</entry>
1124                     </row>
1125                   </tbody>
1126                 </entrytbl>
1127               </row>
1128               <row><entry></entry></row>
1129               <row id="v4l2-mpeg-audio-mode">
1130                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE</constant>&nbsp;</entry>
1131                 <entry>enum&nbsp;v4l2_mpeg_audio_mode</entry>
1132               </row><row><entry spanname="descr">MPEG Audio mode.
1133 Possible values are:</entry>
1134               </row>
1135               <row>
1136                 <entrytbl spanname="descr" cols="2">
1137                   <tbody valign="top">
1138                     <row>
1139                       <entry><constant>V4L2_MPEG_AUDIO_MODE_STEREO</constant>&nbsp;</entry>
1140                       <entry>Stereo</entry>
1141                     </row>
1142                     <row>
1143                       <entry><constant>V4L2_MPEG_AUDIO_MODE_JOINT_STEREO</constant>&nbsp;</entry>
1144                       <entry>Joint Stereo</entry>
1145                     </row>
1146                     <row>
1147                       <entry><constant>V4L2_MPEG_AUDIO_MODE_DUAL</constant>&nbsp;</entry>
1148                       <entry>Bilingual</entry>
1149                     </row>
1150                     <row>
1151                       <entry><constant>V4L2_MPEG_AUDIO_MODE_MONO</constant>&nbsp;</entry>
1152                       <entry>Mono</entry>
1153                     </row>
1154                   </tbody>
1155                 </entrytbl>
1156               </row>
1157               <row><entry></entry></row>
1158               <row id="v4l2-mpeg-audio-mode-extension">
1159                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE_EXTENSION</constant>&nbsp;</entry>
1160                 <entry>enum&nbsp;v4l2_mpeg_audio_mode_extension</entry>
1161               </row><row><entry spanname="descr">Joint Stereo
1162 audio mode extension. In Layer I and II they indicate which subbands
1163 are in intensity stereo. All other subbands are coded in stereo. Layer
1164 III is not (yet) supported. Possible values
1165 are:</entry>
1166               </row>
1167               <row>
1168                 <entrytbl spanname="descr" cols="2">
1169                   <tbody valign="top">
1170                     <row>
1171                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_4</constant>&nbsp;</entry>
1172                       <entry>Subbands 4-31 in intensity stereo</entry>
1173                     </row>
1174                     <row>
1175                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_8</constant>&nbsp;</entry>
1176                       <entry>Subbands 8-31 in intensity stereo</entry>
1177                     </row>
1178                     <row>
1179                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_12</constant>&nbsp;</entry>
1180                       <entry>Subbands 12-31 in intensity stereo</entry>
1181                     </row>
1182                     <row>
1183                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_16</constant>&nbsp;</entry>
1184                       <entry>Subbands 16-31 in intensity stereo</entry>
1185                     </row>
1186                   </tbody>
1187                 </entrytbl>
1188               </row>
1189               <row><entry></entry></row>
1190               <row id="v4l2-mpeg-audio-emphasis">
1191                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_EMPHASIS</constant>&nbsp;</entry>
1192                 <entry>enum&nbsp;v4l2_mpeg_audio_emphasis</entry>
1193               </row><row><entry spanname="descr">Audio Emphasis.
1194 Possible values are:</entry>
1195               </row>
1196               <row>
1197                 <entrytbl spanname="descr" cols="2">
1198                   <tbody valign="top">
1199                     <row>
1200                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_NONE</constant>&nbsp;</entry>
1201                       <entry>None</entry>
1202                     </row>
1203                     <row>
1204                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_50_DIV_15_uS</constant>&nbsp;</entry>
1205                       <entry>50/15 microsecond emphasis</entry>
1206                     </row>
1207                     <row>
1208                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_CCITT_J17</constant>&nbsp;</entry>
1209                       <entry>CCITT J.17</entry>
1210                     </row>
1211                   </tbody>
1212                 </entrytbl>
1213               </row>
1214               <row><entry></entry></row>
1215               <row id="v4l2-mpeg-audio-crc">
1216                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_CRC</constant>&nbsp;</entry>
1217                 <entry>enum&nbsp;v4l2_mpeg_audio_crc</entry>
1218               </row><row><entry spanname="descr">CRC method. Possible
1219 values are:</entry>
1220               </row>
1221               <row>
1222                 <entrytbl spanname="descr" cols="2">
1223                   <tbody valign="top">
1224                     <row>
1225                       <entry><constant>V4L2_MPEG_AUDIO_CRC_NONE</constant>&nbsp;</entry>
1226                       <entry>None</entry>
1227                     </row>
1228                     <row>
1229                       <entry><constant>V4L2_MPEG_AUDIO_CRC_CRC16</constant>&nbsp;</entry>
1230                       <entry>16 bit parity check</entry>
1231                     </row>
1232                   </tbody>
1233                 </entrytbl>
1234               </row>
1235               <row><entry></entry></row>
1236               <row>
1237                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MUTE</constant>&nbsp;</entry>
1238                 <entry>boolean</entry>
1239               </row><row><entry spanname="descr">Mutes the audio when
1240 capturing. This is not done by muting audio hardware, which can still
1241 produce a slight hiss, but in the encoder itself, guaranteeing a fixed
1242 and reproducable audio bitstream. 0 = unmuted, 1 = muted.</entry>
1243               </row>
1244               <row><entry></entry></row>
1245               <row id="v4l2-mpeg-video-encoding">
1246                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ENCODING</constant>&nbsp;</entry>
1247                 <entry>enum&nbsp;v4l2_mpeg_video_encoding</entry>
1248               </row><row><entry spanname="descr">MPEG Video encoding
1249 method. Possible values are:</entry>
1250               </row>
1251               <row>
1252                 <entrytbl spanname="descr" cols="2">
1253                   <tbody valign="top">
1254                     <row>
1255                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_1</constant>&nbsp;</entry>
1256                       <entry>MPEG-1 Video encoding</entry>
1257                     </row>
1258                     <row>
1259                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_2</constant>&nbsp;</entry>
1260                       <entry>MPEG-2 Video encoding</entry>
1261                     </row>
1262                     <row>
1263                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant>&nbsp;</entry>
1264                       <entry>MPEG-4 AVC (H.264) Video encoding</entry>
1265                     </row>
1266                   </tbody>
1267                 </entrytbl>
1268               </row>
1269               <row><entry></entry></row>
1270               <row id="v4l2-mpeg-video-aspect">
1271                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ASPECT</constant>&nbsp;</entry>
1272                 <entry>enum&nbsp;v4l2_mpeg_video_aspect</entry>
1273               </row><row><entry spanname="descr">Video aspect.
1274 Possible values are:</entry>
1275               </row>
1276               <row>
1277                 <entrytbl spanname="descr" cols="2">
1278                   <tbody valign="top">
1279                     <row>
1280                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_1x1</constant>&nbsp;</entry>
1281                     </row>
1282                     <row>
1283                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_4x3</constant>&nbsp;</entry>
1284                     </row>
1285                     <row>
1286                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_16x9</constant>&nbsp;</entry>
1287                     </row>
1288                     <row>
1289                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_221x100</constant>&nbsp;</entry>
1290                     </row>
1291                   </tbody>
1292                 </entrytbl>
1293               </row>
1294               <row><entry></entry></row>
1295               <row>
1296                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_B_FRAMES</constant>&nbsp;</entry>
1297                 <entry>integer</entry>
1298               </row><row><entry spanname="descr">Number of B-Frames
1299 (default 2)</entry>
1300               </row>
1301               <row><entry></entry></row>
1302               <row>
1303                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_SIZE</constant>&nbsp;</entry>
1304                 <entry>integer</entry>
1305               </row><row><entry spanname="descr">GOP size (default
1306 12)</entry>
1307               </row>
1308               <row><entry></entry></row>
1309               <row>
1310                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_CLOSURE</constant>&nbsp;</entry>
1311                 <entry>boolean</entry>
1312               </row><row><entry spanname="descr">GOP closure (default
1313 1)</entry>
1314               </row>
1315               <row><entry></entry></row>
1316               <row>
1317                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_PULLDOWN</constant>&nbsp;</entry>
1318                 <entry>boolean</entry>
1319               </row><row><entry spanname="descr">Enable 3:2 pulldown
1320 (default 0)</entry>
1321               </row>
1322               <row><entry></entry></row>
1323               <row id="v4l2-mpeg-video-bitrate-mode">
1324                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_MODE</constant>&nbsp;</entry>
1325                 <entry>enum&nbsp;v4l2_mpeg_video_bitrate_mode</entry>
1326               </row><row><entry spanname="descr">Video bitrate mode.
1327 Possible values are:</entry>
1328               </row>
1329               <row>
1330                 <entrytbl spanname="descr" cols="2">
1331                   <tbody valign="top">
1332                     <row>
1333                       <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_VBR</constant>&nbsp;</entry>
1334                       <entry>Variable bitrate</entry>
1335                     </row>
1336                     <row>
1337                       <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_CBR</constant>&nbsp;</entry>
1338                       <entry>Constant bitrate</entry>
1339                     </row>
1340                   </tbody>
1341                 </entrytbl>
1342               </row>
1343               <row><entry></entry></row>
1344               <row>
1345                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE</constant>&nbsp;</entry>
1346                 <entry>integer</entry>
1347               </row><row><entry spanname="descr">Video bitrate in bits
1348 per second.</entry>
1349               </row>
1350               <row><entry></entry></row>
1351               <row>
1352                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_PEAK</constant>&nbsp;</entry>
1353                 <entry>integer</entry>
1354               </row><row><entry spanname="descr">Peak video bitrate in
1355 bits per second. Must be larger or equal to the average video bitrate.
1356 It is ignored if the video bitrate mode is set to constant
1357 bitrate.</entry>
1358               </row>
1359               <row><entry></entry></row>
1360               <row>
1361                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION</constant>&nbsp;</entry>
1362                 <entry>integer</entry>
1363               </row><row><entry spanname="descr">For every captured
1364 frame, skip this many subsequent frames (default 0).</entry>
1365               </row>
1366               <row><entry></entry></row>
1367               <row>
1368                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE</constant>&nbsp;</entry>
1369                 <entry>boolean</entry>
1370               </row>
1371               <row><entry spanname="descr">"Mutes" the video to a
1372 fixed color when capturing. This is useful for testing, to produce a
1373 fixed video bitstream. 0 = unmuted, 1 = muted.</entry>
1374               </row>
1375               <row><entry></entry></row>
1376               <row>
1377                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE_YUV</constant>&nbsp;</entry>
1378                 <entry>integer</entry>
1379               </row><row><entry spanname="descr">Sets the "mute" color
1380 of the video. The supplied 32-bit integer is interpreted as follows (bit
1381 0 = least significant bit):</entry>
1382               </row>
1383               <row>
1384                 <entrytbl spanname="descr" cols="2">
1385                   <tbody valign="top">
1386                     <row>
1387                       <entry>Bit 0:7</entry>
1388                       <entry>V chrominance information</entry>
1389                     </row>
1390                     <row>
1391                       <entry>Bit 8:15</entry>
1392                       <entry>U chrominance information</entry>
1393                     </row>
1394                     <row>
1395                       <entry>Bit 16:23</entry>
1396                       <entry>Y luminance information</entry>
1397                     </row>
1398                     <row>
1399                       <entry>Bit 24:31</entry>
1400                       <entry>Must be zero.</entry>
1401                     </row>
1402                   </tbody>
1403                 </entrytbl>
1404               </row>
1405             </tbody>
1406           </tgroup>
1407         </table>
1408       </section>
1409
1410       <section>
1411         <title>CX2341x MPEG Controls</title>
1412
1413         <para>The following MPEG class controls deal with MPEG
1414 encoding settings that are specific to the Conexant CX23415 and
1415 CX23416 MPEG encoding chips.</para>
1416
1417         <table pgwide="1" frame="none" id="cx2341x-control-id">
1418           <title>CX2341x Control IDs</title>
1419           <tgroup cols="4">
1420             <colspec colname="c1" colwidth="1*" />
1421             <colspec colname="c2" colwidth="6*" />
1422             <colspec colname="c3" colwidth="2*" />
1423             <colspec colname="c4" colwidth="6*" />
1424             <spanspec namest="c1" nameend="c2" spanname="id" />
1425             <spanspec namest="c2" nameend="c4" spanname="descr" />
1426             <thead>
1427               <row>
1428                 <entry spanname="id" align="left">ID</entry>
1429                 <entry align="left">Type</entry>
1430               </row><row><entry spanname="descr" align="left">Description</entry>
1431               </row>
1432             </thead>
1433             <tbody valign="top">
1434               <row><entry></entry></row>
1435               <row id="v4l2-mpeg-cx2341x-video-spatial-filter-mode">
1436                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE</constant>&nbsp;</entry>
1437                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_spatial_filter_mode</entry>
1438               </row><row><entry spanname="descr">Sets the Spatial
1439 Filter mode (default <constant>MANUAL</constant>). Possible values
1440 are:</entry>
1441               </row>
1442               <row>
1443                 <entrytbl spanname="descr" cols="2">
1444                   <tbody valign="top">
1445                     <row>
1446                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1447                       <entry>Choose the filter manually</entry>
1448                     </row>
1449                     <row>
1450                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1451                       <entry>Choose the filter automatically</entry>
1452                     </row>
1453                   </tbody>
1454                 </entrytbl>
1455               </row>
1456               <row><entry></entry></row>
1457               <row>
1458                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER</constant>&nbsp;</entry>
1459                 <entry>integer&nbsp;(0-15)</entry>
1460               </row><row><entry spanname="descr">The setting for the
1461 Spatial Filter. 0 = off, 15 = maximum. (Default is 0.)</entry>
1462               </row>
1463               <row><entry></entry></row>
1464               <row id="luma-spatial-filter-type">
1465                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1466                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_luma_spatial_filter_type</entry>
1467               </row><row><entry spanname="descr">Select the algorithm
1468 to use for the Luma Spatial Filter (default
1469 <constant>1D_HOR</constant>). Possible values:</entry>
1470               </row>
1471               <row>
1472                 <entrytbl spanname="descr" cols="2">
1473                   <tbody valign="top">
1474                     <row>
1475                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1476                       <entry>No filter</entry>
1477                     </row>
1478                     <row>
1479                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1480                       <entry>One-dimensional horizontal</entry>
1481                     </row>
1482                     <row>
1483                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_VERT</constant>&nbsp;</entry>
1484                       <entry>One-dimensional vertical</entry>
1485                     </row>
1486                     <row>
1487                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_HV_SEPARABLE</constant>&nbsp;</entry>
1488                       <entry>Two-dimensional separable</entry>
1489                     </row>
1490                     <row>
1491                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_SYM_NON_SEPARABLE</constant>&nbsp;</entry>
1492                       <entry>Two-dimensional symmetrical
1493 non-separable</entry>
1494                     </row>
1495                   </tbody>
1496                 </entrytbl>
1497               </row>
1498               <row><entry></entry></row>
1499               <row id="chroma-spatial-filter-type">
1500                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1501                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_chroma_spatial_filter_type</entry>
1502               </row><row><entry spanname="descr">Select the algorithm
1503 for the Chroma Spatial Filter (default <constant>1D_HOR</constant>).
1504 Possible values are:</entry>
1505               </row>
1506               <row>
1507                 <entrytbl spanname="descr" cols="2">
1508                   <tbody valign="top">
1509                     <row>
1510                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1511                       <entry>No filter</entry>
1512                     </row>
1513                     <row>
1514                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1515                       <entry>One-dimensional horizontal</entry>
1516                     </row>
1517                   </tbody>
1518                 </entrytbl>
1519               </row>
1520               <row><entry></entry></row>
1521               <row id="v4l2-mpeg-cx2341x-video-temporal-filter-mode">
1522                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE</constant>&nbsp;</entry>
1523                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_temporal_filter_mode</entry>
1524               </row><row><entry spanname="descr">Sets the Temporal
1525 Filter mode (default <constant>MANUAL</constant>). Possible values
1526 are:</entry>
1527               </row>
1528               <row>
1529                 <entrytbl spanname="descr" cols="2">
1530                   <tbody valign="top">
1531                     <row>
1532                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1533                       <entry>Choose the filter manually</entry>
1534                     </row>
1535                     <row>
1536                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1537                       <entry>Choose the filter automatically</entry>
1538                     </row>
1539                   </tbody>
1540                 </entrytbl>
1541               </row>
1542               <row><entry></entry></row>
1543               <row>
1544                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER</constant>&nbsp;</entry>
1545                 <entry>integer&nbsp;(0-31)</entry>
1546               </row><row><entry spanname="descr">The setting for the
1547 Temporal Filter. 0 = off, 31 = maximum. (Default is 8 for full-scale
1548 capturing and 0 for scaled capturing.)</entry>
1549               </row>
1550               <row><entry></entry></row>
1551               <row id="v4l2-mpeg-cx2341x-video-median-filter-type">
1552                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE</constant>&nbsp;</entry>
1553                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_median_filter_type</entry>
1554               </row><row><entry spanname="descr">Median Filter Type
1555 (default <constant>OFF</constant>). Possible values are:</entry>
1556               </row>
1557               <row>
1558                 <entrytbl spanname="descr" cols="2">
1559                   <tbody valign="top">
1560                     <row>
1561                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1562                       <entry>No filter</entry>
1563                     </row>
1564                     <row>
1565                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR</constant>&nbsp;</entry>
1566                       <entry>Horizontal filter</entry>
1567                     </row>
1568                     <row>
1569                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_VERT</constant>&nbsp;</entry>
1570                       <entry>Vertical filter</entry>
1571                     </row>
1572                     <row>
1573                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR_VERT</constant>&nbsp;</entry>
1574                       <entry>Horizontal and vertical filter</entry>
1575                     </row>
1576                     <row>
1577                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_DIAG</constant>&nbsp;</entry>
1578                       <entry>Diagonal filter</entry>
1579                     </row>
1580                   </tbody>
1581                 </entrytbl>
1582               </row>
1583               <row><entry></entry></row>
1584               <row>
1585                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1586                 <entry>integer&nbsp;(0-255)</entry>
1587               </row><row><entry spanname="descr">Threshold above which
1588 the luminance median filter is enabled (default 0)</entry>
1589               </row>
1590               <row><entry></entry></row>
1591               <row>
1592                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1593                 <entry>integer&nbsp;(0-255)</entry>
1594               </row><row><entry spanname="descr">Threshold below which
1595 the luminance median filter is enabled (default 255)</entry>
1596               </row>
1597               <row><entry></entry></row>
1598               <row>
1599                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1600                 <entry>integer&nbsp;(0-255)</entry>
1601               </row><row><entry spanname="descr">Threshold above which
1602 the chroma median filter is enabled (default 0)</entry>
1603               </row>
1604               <row><entry></entry></row>
1605               <row>
1606                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1607                 <entry>integer&nbsp;(0-255)</entry>
1608               </row><row><entry spanname="descr">Threshold below which
1609 the chroma median filter is enabled (default 255)</entry>
1610               </row>
1611               <row><entry></entry></row>
1612               <row>
1613                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_STREAM_INSERT_NAV_PACKETS</constant>&nbsp;</entry>
1614                 <entry>boolean</entry>
1615               </row>
1616               <row><entry spanname="descr">The CX2341X MPEG encoder
1617 can insert one empty MPEG-2 PES packet into the stream between every
1618 four video frames. The packet size is 2048 bytes, including the
1619 packet_start_code_prefix and stream_id fields. The stream_id is 0xBF
1620 (private stream 2). The payload consists of 0x00 bytes, to be filled
1621 in by the application. 0 = do not insert, 1 = insert packets.</entry>
1622               </row>
1623             </tbody>
1624           </tgroup>
1625         </table>
1626       </section>
1627     </section>
1628
1629     <section id="camera-controls">
1630       <title>Camera Control Reference</title>
1631
1632       <para>The Camera class includes controls for mechanical (or
1633 equivalent digital) features of a device such as controllable lenses
1634 or sensors.</para>
1635
1636     <table pgwide="1" frame="none" id="camera-control-id">
1637       <title>Camera Control IDs</title>
1638       <tgroup cols="4">
1639         <colspec colname="c1" colwidth="1*" />
1640         <colspec colname="c2" colwidth="6*" />
1641         <colspec colname="c3" colwidth="2*" />
1642         <colspec colname="c4" colwidth="6*" />
1643         <spanspec namest="c1" nameend="c2" spanname="id" />
1644         <spanspec namest="c2" nameend="c4" spanname="descr" />
1645         <thead>
1646           <row>
1647             <entry spanname="id" align="left">ID</entry>
1648             <entry align="left">Type</entry>
1649           </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1650           </row>
1651         </thead>
1652         <tbody valign="top">
1653           <row><entry></entry></row>
1654           <row>
1655             <entry spanname="id"><constant>V4L2_CID_CAMERA_CLASS</constant>&nbsp;</entry>
1656             <entry>class</entry>
1657           </row><row><entry spanname="descr">The Camera class
1658 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1659 description of this control class.</entry>
1660           </row>
1661           <row><entry></entry></row>
1662
1663           <row id="v4l2-exposure-auto-type">
1664             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO</constant>&nbsp;</entry>
1665             <entry>enum&nbsp;v4l2_exposure_auto_type</entry>
1666           </row><row><entry spanname="descr">Enables automatic
1667 adjustments of the exposure time and/or iris aperture. The effect of
1668 manual changes of the exposure time or iris aperture while these
1669 features are enabled is undefined, drivers should ignore such
1670 requests. Possible values are:</entry>
1671           </row>
1672           <row>
1673             <entrytbl spanname="descr" cols="2">
1674               <tbody valign="top">
1675                 <row>
1676                   <entry><constant>V4L2_EXPOSURE_AUTO</constant>&nbsp;</entry>
1677                       <entry>Automatic exposure time, automatic iris
1678 aperture.</entry>
1679                 </row>
1680                 <row>
1681                   <entry><constant>V4L2_EXPOSURE_MANUAL</constant>&nbsp;</entry>
1682                   <entry>Manual exposure time, manual iris.</entry>
1683                 </row>
1684                 <row>
1685                   <entry><constant>V4L2_EXPOSURE_SHUTTER_PRIORITY</constant>&nbsp;</entry>
1686                   <entry>Manual exposure time, auto iris.</entry>
1687                 </row>
1688                 <row>
1689                   <entry><constant>V4L2_EXPOSURE_APERTURE_PRIORITY</constant>&nbsp;</entry>
1690                   <entry>Auto exposure time, manual iris.</entry>
1691                 </row>
1692               </tbody>
1693             </entrytbl>
1694           </row>
1695           <row><entry></entry></row>
1696
1697           <row>
1698             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>&nbsp;</entry>
1699             <entry>integer</entry>
1700           </row><row><entry spanname="descr">Determines the exposure
1701 time of the camera sensor. The exposure time is limited by the frame
1702 interval. Drivers should interpret the values as 100 &micro;s units,
1703 where the value 1 stands for 1/10000th of a second, 10000 for 1 second
1704 and 100000 for 10 seconds.</entry>
1705           </row>
1706           <row><entry></entry></row>
1707
1708           <row>
1709             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>&nbsp;</entry>
1710             <entry>boolean</entry>
1711           </row><row><entry spanname="descr">When
1712 <constant>V4L2_CID_EXPOSURE_AUTO</constant> is set to
1713 <constant>AUTO</constant> or <constant>APERTURE_PRIORITY</constant>,
1714 this control determines if the device may dynamically vary the frame
1715 rate. By default this feature is disabled (0) and the frame rate must
1716 remain constant.</entry>
1717           </row>
1718           <row><entry></entry></row>
1719
1720           <row>
1721             <entry spanname="id"><constant>V4L2_CID_PAN_RELATIVE</constant>&nbsp;</entry>
1722             <entry>integer</entry>
1723           </row><row><entry spanname="descr">This control turns the
1724 camera horizontally by the specified amount. The unit is undefined. A
1725 positive value moves the camera to the right (clockwise when viewed
1726 from above), a negative value to the left. A value of zero does not
1727 cause motion. This is a write-only control.</entry>
1728           </row>
1729           <row><entry></entry></row>
1730
1731           <row>
1732             <entry spanname="id"><constant>V4L2_CID_TILT_RELATIVE</constant>&nbsp;</entry>
1733             <entry>integer</entry>
1734           </row><row><entry spanname="descr">This control turns the
1735 camera vertically by the specified amount. The unit is undefined. A
1736 positive value moves the camera up, a negative value down. A value of
1737 zero does not cause motion. This is a write-only control.</entry>
1738           </row>
1739           <row><entry></entry></row>
1740
1741           <row>
1742             <entry spanname="id"><constant>V4L2_CID_PAN_RESET</constant>&nbsp;</entry>
1743             <entry>button</entry>
1744           </row><row><entry spanname="descr">When this control is set,
1745 the camera moves horizontally to the default position.</entry>
1746           </row>
1747           <row><entry></entry></row>
1748
1749           <row>
1750             <entry spanname="id"><constant>V4L2_CID_TILT_RESET</constant>&nbsp;</entry>
1751             <entry>button</entry>
1752           </row><row><entry spanname="descr">When this control is set,
1753 the camera moves vertically to the default position.</entry>
1754           </row>
1755           <row><entry></entry></row>
1756
1757           <row>
1758             <entry spanname="id"><constant>V4L2_CID_PAN_ABSOLUTE</constant>&nbsp;</entry>
1759             <entry>integer</entry>
1760           </row><row><entry spanname="descr">This control
1761 turns the camera horizontally to the specified position. Positive
1762 values move the camera to the right (clockwise when viewed from above),
1763 negative values to the left. Drivers should interpret the values as arc
1764 seconds, with valid values between -180 * 3600 and +180 * 3600
1765 inclusive.</entry>
1766           </row>
1767           <row><entry></entry></row>
1768
1769           <row>
1770             <entry spanname="id"><constant>V4L2_CID_TILT_ABSOLUTE</constant>&nbsp;</entry>
1771             <entry>integer</entry>
1772           </row><row><entry spanname="descr">This control
1773 turns the camera vertically to the specified position. Positive values
1774 move the camera up, negative values down. Drivers should interpret the
1775 values as arc seconds, with valid values between -180 * 3600 and +180
1776 * 3600 inclusive.</entry>
1777           </row>
1778           <row><entry></entry></row>
1779
1780           <row>
1781             <entry spanname="id"><constant>V4L2_CID_FOCUS_ABSOLUTE</constant>&nbsp;</entry>
1782             <entry>integer</entry>
1783           </row><row><entry spanname="descr">This control sets the
1784 focal point of the camera to the specified position. The unit is
1785 undefined. Positive values set the focus closer to the camera,
1786 negative values towards infinity.</entry>
1787           </row>
1788           <row><entry></entry></row>
1789
1790           <row>
1791             <entry spanname="id"><constant>V4L2_CID_FOCUS_RELATIVE</constant>&nbsp;</entry>
1792             <entry>integer</entry>
1793           </row><row><entry spanname="descr">This control moves the
1794 focal point of the camera by the specified amount. The unit is
1795 undefined. Positive values move the focus closer to the camera,
1796 negative values towards infinity. This is a write-only control.</entry>
1797           </row>
1798           <row><entry></entry></row>
1799
1800           <row>
1801             <entry spanname="id"><constant>V4L2_CID_FOCUS_AUTO</constant>&nbsp;</entry>
1802             <entry>boolean</entry>
1803           </row><row><entry spanname="descr">Enables automatic focus
1804 adjustments. The effect of manual focus adjustments while this feature
1805 is enabled is undefined, drivers should ignore such requests.</entry>
1806           </row>
1807           <row><entry></entry></row>
1808
1809           <row>
1810             <entry spanname="id"><constant>V4L2_CID_ZOOM_ABSOLUTE</constant>&nbsp;</entry>
1811             <entry>integer</entry>
1812           </row><row><entry spanname="descr">Specify the objective lens
1813 focal length as an absolute value. The zoom unit is driver-specific and its
1814 value should be a positive integer.</entry>
1815           </row>
1816           <row><entry></entry></row>
1817
1818           <row>
1819             <entry spanname="id"><constant>V4L2_CID_ZOOM_RELATIVE</constant>&nbsp;</entry>
1820             <entry>integer</entry>
1821           </row><row><entry spanname="descr">Specify the objective lens
1822 focal length relatively to the current value. Positive values move the zoom
1823 lens group towards the telephoto direction, negative values towards the
1824 wide-angle direction. The zoom unit is driver-specific. This is a write-only control.</entry>
1825           </row>
1826           <row><entry></entry></row>
1827
1828           <row>
1829             <entry spanname="id"><constant>V4L2_CID_ZOOM_CONTINUOUS</constant>&nbsp;</entry>
1830             <entry>integer</entry>
1831           </row><row><entry spanname="descr">Move the objective lens group
1832 at the specified speed until it reaches physical device limits or until an
1833 explicit request to stop the movement. A positive value moves the zoom lens
1834 group towards the telephoto direction. A value of zero stops the zoom lens
1835 group movement. A negative value moves the zoom lens group towards the
1836 wide-angle direction. The zoom speed unit is driver-specific.</entry>
1837           </row>
1838           <row><entry></entry></row>
1839
1840           <row>
1841             <entry spanname="id"><constant>V4L2_CID_IRIS_ABSOLUTE</constant>&nbsp;</entry>
1842             <entry>integer</entry>
1843           </row><row><entry spanname="descr">This control sets the
1844 camera's aperture to the specified value. The unit is undefined.
1845 Larger values open the iris wider, smaller values close it.</entry>
1846           </row>
1847           <row><entry></entry></row>
1848
1849           <row>
1850             <entry spanname="id"><constant>V4L2_CID_IRIS_RELATIVE</constant>&nbsp;</entry>
1851             <entry>integer</entry>
1852           </row><row><entry spanname="descr">This control modifies the
1853 camera's aperture by the specified amount. The unit is undefined.
1854 Positive values open the iris one step further, negative values close
1855 it one step further. This is a write-only control.</entry>
1856           </row>
1857           <row><entry></entry></row>
1858
1859           <row>
1860             <entry spanname="id"><constant>V4L2_CID_PRIVACY</constant>&nbsp;</entry>
1861             <entry>boolean</entry>
1862           </row><row><entry spanname="descr">Prevent video from being acquired
1863 by the camera. When this control is set to <constant>TRUE</constant> (1), no
1864 image can be captured by the camera. Common means to enforce privacy are
1865 mechanical obturation of the sensor and firmware image processing, but the
1866 device is not restricted to these methods. Devices that implement the privacy
1867 control must support read access and may support write access.</entry>
1868           </row>
1869
1870           <row>
1871             <entry spanname="id"><constant>V4L2_CID_BAND_STOP_FILTER</constant>&nbsp;</entry>
1872             <entry>integer</entry>
1873           </row><row><entry spanname="descr">Switch the band-stop filter of a
1874 camera sensor on or off, or specify its strength. Such band-stop filters can
1875 be used, for example, to filter out the fluorescent light component.</entry>
1876           </row>
1877           <row><entry></entry></row>
1878         </tbody>
1879       </tgroup>
1880     </table>
1881   </section>
1882
1883     <section id="fm-tx-controls">
1884       <title>FM Transmitter Control Reference</title>
1885
1886       <para>The FM Transmitter (FM_TX) class includes controls for common features of
1887 FM transmissions capable devices. Currently this class includes parameters for audio
1888 compression, pilot tone generation, audio deviation limiter, RDS transmission and
1889 tuning power features.</para>
1890
1891       <table pgwide="1" frame="none" id="fm-tx-control-id">
1892       <title>FM_TX Control IDs</title>
1893
1894       <tgroup cols="4">
1895         <colspec colname="c1" colwidth="1*" />
1896         <colspec colname="c2" colwidth="6*" />
1897         <colspec colname="c3" colwidth="2*" />
1898         <colspec colname="c4" colwidth="6*" />
1899         <spanspec namest="c1" nameend="c2" spanname="id" />
1900         <spanspec namest="c2" nameend="c4" spanname="descr" />
1901         <thead>
1902           <row>
1903             <entry spanname="id" align="left">ID</entry>
1904             <entry align="left">Type</entry>
1905           </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1906           </row>
1907         </thead>
1908         <tbody valign="top">
1909           <row><entry></entry></row>
1910           <row>
1911             <entry spanname="id"><constant>V4L2_CID_FM_TX_CLASS</constant>&nbsp;</entry>
1912             <entry>class</entry>
1913           </row><row><entry spanname="descr">The FM_TX class
1914 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1915 description of this control class.</entry>
1916           </row>
1917           <row>
1918             <entry spanname="id"><constant>V4L2_CID_RDS_TX_DEVIATION</constant>&nbsp;</entry>
1919             <entry>integer</entry>
1920           </row>
1921           <row><entry spanname="descr">Configures RDS signal frequency deviation level in Hz.
1922 The range and step are driver-specific.</entry>
1923           </row>
1924           <row>
1925             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PI</constant>&nbsp;</entry>
1926             <entry>integer</entry>
1927           </row>
1928           <row><entry spanname="descr">Sets the RDS Programme Identification field
1929 for transmission.</entry>
1930           </row>
1931           <row>
1932             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PTY</constant>&nbsp;</entry>
1933             <entry>integer</entry>
1934           </row>
1935           <row><entry spanname="descr">Sets the RDS Programme Type field for transmission.
1936 This encodes up to 31 pre-defined programme types.</entry>
1937           </row>
1938           <row>
1939             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PS_NAME</constant>&nbsp;</entry>
1940             <entry>string</entry>
1941           </row>
1942           <row><entry spanname="descr">Sets the Programme Service name (PS_NAME) for transmission.
1943 It is intended for static display on a receiver. It is the primary aid to listeners in programme service
1944 identification and selection.  In Annex E of <xref linkend="en50067" />, the RDS specification,
1945 there is a full description of the correct character encoding for Programme Service name strings.
1946 Also from RDS specification, PS is usually a single eight character text. However, it is also possible
1947 to find receivers which can scroll strings sized as 8 x N characters. So, this control must be configured
1948 with steps of 8 characters. The result is it must always contain a string with size multiple of 8.</entry>
1949           </row>
1950           <row>
1951             <entry spanname="id"><constant>V4L2_CID_RDS_TX_RADIO_TEXT</constant>&nbsp;</entry>
1952             <entry>string</entry>
1953           </row>
1954           <row><entry spanname="descr">Sets the Radio Text info for transmission. It is a textual description of
1955 what is being broadcasted. RDS Radio Text can be applied when broadcaster wishes to transmit longer PS names,
1956 programme-related information or any other text. In these cases, RadioText should be used in addition to
1957 <constant>V4L2_CID_RDS_TX_PS_NAME</constant>. The encoding for Radio Text strings is also fully described
1958 in Annex E of <xref linkend="en50067" />. The length of Radio Text strings depends on which RDS Block is being
1959 used to transmit it, either 32 (2A block) or 64 (2B block).  However, it is also possible
1960 to find receivers which can scroll strings sized as 32 x N or 64 x N characters. So, this control must be configured
1961 with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. </entry>
1962           </row>
1963           <row>
1964             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_ENABLED</constant>&nbsp;</entry>
1965             <entry>boolean</entry>
1966           </row>
1967           <row><entry spanname="descr">Enables or disables the audio deviation limiter feature.
1968 The limiter is useful when trying to maximize the audio volume, minimize receiver-generated
1969 distortion and prevent overmodulation.
1970 </entry>
1971           </row>
1972           <row>
1973             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_RELEASE_TIME</constant>&nbsp;</entry>
1974             <entry>integer</entry>
1975           </row>
1976           <row><entry spanname="descr">Sets the audio deviation limiter feature release time.
1977 Unit is in useconds. Step and range are driver-specific.</entry>
1978           </row>
1979           <row>
1980             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_DEVIATION</constant>&nbsp;</entry>
1981             <entry>integer</entry>
1982           </row>
1983           <row><entry spanname="descr">Configures audio frequency deviation level in Hz.
1984 The range and step are driver-specific.</entry>
1985           </row>
1986           <row>
1987             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ENABLED</constant>&nbsp;</entry>
1988             <entry>boolean</entry>
1989           </row>
1990           <row><entry spanname="descr">Enables or disables the audio compression feature.
1991 This feature amplifies signals below the threshold by a fixed gain and compresses audio
1992 signals above the threshold by the ratio of Threshold/(Gain + Threshold).</entry>
1993           </row>
1994           <row>
1995             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_GAIN</constant>&nbsp;</entry>
1996             <entry>integer</entry>
1997           </row>
1998           <row><entry spanname="descr">Sets the gain for audio compression feature. It is
1999 a dB value. The range and step are driver-specific.</entry>
2000           </row>
2001           <row>
2002             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_THRESHOLD</constant>&nbsp;</entry>
2003             <entry>integer</entry>
2004           </row>
2005           <row><entry spanname="descr">Sets the threshold level for audio compression freature.
2006 It is a dB value. The range and step are driver-specific.</entry>
2007           </row>
2008           <row>
2009             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME</constant>&nbsp;</entry>
2010             <entry>integer</entry>
2011           </row>
2012           <row><entry spanname="descr">Sets the attack time for audio compression feature.
2013 It is a useconds value. The range and step are driver-specific.</entry>
2014           </row>
2015           <row>
2016             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME</constant>&nbsp;</entry>
2017             <entry>integer</entry>
2018           </row>
2019           <row><entry spanname="descr">Sets the release time for audio compression feature.
2020 It is a useconds value. The range and step are driver-specific.</entry>
2021           </row>
2022           <row>
2023             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_ENABLED</constant>&nbsp;</entry>
2024             <entry>boolean</entry>
2025           </row>
2026           <row><entry spanname="descr">Enables or disables the pilot tone generation feature.</entry>
2027           </row>
2028           <row>
2029             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_DEVIATION</constant>&nbsp;</entry>
2030             <entry>integer</entry>
2031           </row>
2032           <row><entry spanname="descr">Configures pilot tone frequency deviation level. Unit is
2033 in Hz. The range and step are driver-specific.</entry>
2034           </row>
2035           <row>
2036             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_FREQUENCY</constant>&nbsp;</entry>
2037             <entry>integer</entry>
2038           </row>
2039           <row><entry spanname="descr">Configures pilot tone frequency value. Unit is
2040 in Hz. The range and step are driver-specific.</entry>
2041           </row>
2042           <row>
2043             <entry spanname="id"><constant>V4L2_CID_TUNE_PREEMPHASIS</constant>&nbsp;</entry>
2044             <entry>integer</entry>
2045           </row>
2046           <row id="v4l2-preemphasis"><entry spanname="descr">Configures the pre-emphasis value for broadcasting.
2047 A pre-emphasis filter is applied to the broadcast to accentuate the high audio frequencies.
2048 Depending on the region, a time constant of either 50 or 75 useconds is used. The enum&nbsp;v4l2_preemphasis
2049 defines possible values for pre-emphasis. Here they are:</entry>
2050         </row><row>
2051         <entrytbl spanname="descr" cols="2">
2052                   <tbody valign="top">
2053                     <row>
2054                       <entry><constant>V4L2_PREEMPHASIS_DISABLED</constant>&nbsp;</entry>
2055                       <entry>No pre-emphasis is applied.</entry>
2056                     </row>
2057                     <row>
2058                       <entry><constant>V4L2_PREEMPHASIS_50_uS</constant>&nbsp;</entry>
2059                       <entry>A pre-emphasis of 50 uS is used.</entry>
2060                     </row>
2061                     <row>
2062                       <entry><constant>V4L2_PREEMPHASIS_75_uS</constant>&nbsp;</entry>
2063                       <entry>A pre-emphasis of 75 uS is used.</entry>
2064                     </row>
2065                   </tbody>
2066                 </entrytbl>
2067
2068           </row>
2069           <row>
2070             <entry spanname="id"><constant>V4L2_CID_TUNE_POWER_LEVEL</constant>&nbsp;</entry>
2071             <entry>integer</entry>
2072           </row>
2073           <row><entry spanname="descr">Sets the output power level for signal transmission.
2074 Unit is in dBuV. Range and step are driver-specific.</entry>
2075           </row>
2076           <row>
2077             <entry spanname="id"><constant>V4L2_CID_TUNE_ANTENNA_CAPACITOR</constant>&nbsp;</entry>
2078             <entry>integer</entry>
2079           </row>
2080           <row><entry spanname="descr">This selects the value of antenna tuning capacitor
2081 manually or automatically if set to zero. Unit, range and step are driver-specific.</entry>
2082           </row>
2083           <row><entry></entry></row>
2084         </tbody>
2085       </tgroup>
2086       </table>
2087
2088 <para>For more details about RDS specification, refer to
2089 <xref linkend="en50067" /> document, from CENELEC.</para>
2090     </section>
2091 </section>
2092
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