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