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1 <section id="control">
2 <title>User Controls</title>
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>
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>
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>
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 ⪚ 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>
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 & 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_LASTP1</constant></entry>
285 <entry></entry>
286 <entry>End of the predefined control IDs (currently
287 <constant>V4L2_CID_COLORFX</constant> + 1).</entry>
288 </row>
289 <row>
290 <entry><constant>V4L2_CID_PRIVATE_BASE</constant></entry>
291 <entry></entry>
292 <entry>ID of the first custom (driver specific) control.
293 Applications depending on particular custom controls should check the
294 driver name and version, see <xref linkend="querycap" />.</entry>
295 </row>
296 </tbody>
297 </tgroup>
298 </table>
300 <para>Applications can enumerate the available controls with the
301 &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls, get and set a
302 control value with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls.
303 Drivers must implement <constant>VIDIOC_QUERYCTRL</constant>,
304 <constant>VIDIOC_G_CTRL</constant> and
305 <constant>VIDIOC_S_CTRL</constant> when the device has one or more
306 controls, <constant>VIDIOC_QUERYMENU</constant> when it has one or
307 more menu type controls.</para>
309 <example>
310 <title>Enumerating all controls</title>
312 <programlisting>
313 &v4l2-queryctrl; queryctrl;
314 &v4l2-querymenu; querymenu;
316 static void
317 enumerate_menu (void)
318 {
319 printf (" Menu items:\n");
321 memset (&querymenu, 0, sizeof (querymenu));
322 querymenu.id = queryctrl.id;
324 for (querymenu.index = queryctrl.minimum;
325 querymenu.index <= queryctrl.maximum;
326 querymenu.index++) {
327 if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &querymenu)) {
328 printf (" %s\n", querymenu.name);
329 } else {
330 perror ("VIDIOC_QUERYMENU");
331 exit (EXIT_FAILURE);
332 }
333 }
334 }
336 memset (&queryctrl, 0, sizeof (queryctrl));
338 for (queryctrl.id = V4L2_CID_BASE;
339 queryctrl.id < V4L2_CID_LASTP1;
340 queryctrl.id++) {
341 if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) {
342 if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED)
343 continue;
345 printf ("Control %s\n", queryctrl.name);
347 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
348 enumerate_menu ();
349 } else {
350 if (errno == EINVAL)
351 continue;
353 perror ("VIDIOC_QUERYCTRL");
354 exit (EXIT_FAILURE);
355 }
356 }
358 for (queryctrl.id = V4L2_CID_PRIVATE_BASE;;
359 queryctrl.id++) {
360 if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) {
361 if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED)
362 continue;
364 printf ("Control %s\n", queryctrl.name);
366 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
367 enumerate_menu ();
368 } else {
369 if (errno == EINVAL)
370 break;
372 perror ("VIDIOC_QUERYCTRL");
373 exit (EXIT_FAILURE);
374 }
375 }
376 </programlisting>
377 </example>
379 <example>
380 <title>Changing controls</title>
382 <programlisting>
383 &v4l2-queryctrl; queryctrl;
384 &v4l2-control; control;
386 memset (&queryctrl, 0, sizeof (queryctrl));
387 queryctrl.id = V4L2_CID_BRIGHTNESS;
389 if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &queryctrl)) {
390 if (errno != EINVAL) {
391 perror ("VIDIOC_QUERYCTRL");
392 exit (EXIT_FAILURE);
393 } else {
394 printf ("V4L2_CID_BRIGHTNESS is not supported\n");
395 }
396 } else if (queryctrl.flags & V4L2_CTRL_FLAG_DISABLED) {
397 printf ("V4L2_CID_BRIGHTNESS is not supported\n");
398 } else {
399 memset (&control, 0, sizeof (control));
400 control.id = V4L2_CID_BRIGHTNESS;
401 control.value = queryctrl.default_value;
403 if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &control)) {
404 perror ("VIDIOC_S_CTRL");
405 exit (EXIT_FAILURE);
406 }
407 }
409 memset (&control, 0, sizeof (control));
410 control.id = V4L2_CID_CONTRAST;
412 if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &control)) {
413 control.value += 1;
415 /* The driver may clamp the value or return ERANGE, ignored here */
417 if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &control)
418 && errno != ERANGE) {
419 perror ("VIDIOC_S_CTRL");
420 exit (EXIT_FAILURE);
421 }
422 /* Ignore if V4L2_CID_CONTRAST is unsupported */
423 } else if (errno != EINVAL) {
424 perror ("VIDIOC_G_CTRL");
425 exit (EXIT_FAILURE);
426 }
428 control.id = V4L2_CID_AUDIO_MUTE;
429 control.value = TRUE; /* silence */
431 /* Errors ignored */
432 ioctl (fd, VIDIOC_S_CTRL, &control);
433 </programlisting>
434 </example>
435 </section>
437 <section id="extended-controls">
438 <title>Extended Controls</title>
440 <section>
441 <title>Introduction</title>
443 <para>The control mechanism as originally designed was meant
444 to be used for user settings (brightness, saturation, etc). However,
445 it turned out to be a very useful model for implementing more
446 complicated driver APIs where each driver implements only a subset of
447 a larger API.</para>
449 <para>The MPEG encoding API was the driving force behind
450 designing and implementing this extended control mechanism: the MPEG
451 standard is quite large and the currently supported hardware MPEG
452 encoders each only implement a subset of this standard. Further more,
453 many parameters relating to how the video is encoded into an MPEG
454 stream are specific to the MPEG encoding chip since the MPEG standard
455 only defines the format of the resulting MPEG stream, not how the
456 video is actually encoded into that format.</para>
458 <para>Unfortunately, the original control API lacked some
459 features needed for these new uses and so it was extended into the
460 (not terribly originally named) extended control API.</para>
462 <para>Even though the MPEG encoding API was the first effort
463 to use the Extended Control API, nowadays there are also other classes
464 of Extended Controls, such as Camera Controls and FM Transmitter Controls.
465 The Extended Controls API as well as all Extended Controls classes are
466 described in the following text.</para>
467 </section>
469 <section>
470 <title>The Extended Control API</title>
472 <para>Three new ioctls are available: &VIDIOC-G-EXT-CTRLS;,
473 &VIDIOC-S-EXT-CTRLS; and &VIDIOC-TRY-EXT-CTRLS;. These ioctls act on
474 arrays of controls (as opposed to the &VIDIOC-G-CTRL; and
475 &VIDIOC-S-CTRL; ioctls that act on a single control). This is needed
476 since it is often required to atomically change several controls at
477 once.</para>
479 <para>Each of the new ioctls expects a pointer to a
480 &v4l2-ext-controls;. This structure contains a pointer to the control
481 array, a count of the number of controls in that array and a control
482 class. Control classes are used to group similar controls into a
483 single class. For example, control class
484 <constant>V4L2_CTRL_CLASS_USER</constant> contains all user controls
485 (&ie; all controls that can also be set using the old
486 <constant>VIDIOC_S_CTRL</constant> ioctl). Control class
487 <constant>V4L2_CTRL_CLASS_MPEG</constant> contains all controls
488 relating to MPEG encoding, etc.</para>
490 <para>All controls in the control array must belong to the
491 specified control class. An error is returned if this is not the
492 case.</para>
494 <para>It is also possible to use an empty control array (count
495 == 0) to check whether the specified control class is
496 supported.</para>
498 <para>The control array is a &v4l2-ext-control; array. The
499 <structname>v4l2_ext_control</structname> structure is very similar to
500 &v4l2-control;, except for the fact that it also allows for 64-bit
501 values and pointers to be passed.</para>
503 <para>It is important to realize that due to the flexibility of
504 controls it is necessary to check whether the control you want to set
505 actually is supported in the driver and what the valid range of values
506 is. So use the &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls to
507 check this. Also note that it is possible that some of the menu
508 indices in a control of type <constant>V4L2_CTRL_TYPE_MENU</constant>
509 may not be supported (<constant>VIDIOC_QUERYMENU</constant> will
510 return an error). A good example is the list of supported MPEG audio
511 bitrates. Some drivers only support one or two bitrates, others
512 support a wider range.</para>
513 </section>
515 <section>
516 <title>Enumerating Extended Controls</title>
518 <para>The recommended way to enumerate over the extended
519 controls is by using &VIDIOC-QUERYCTRL; in combination with the
520 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag:</para>
522 <informalexample>
523 <programlisting>
524 &v4l2-queryctrl; qctrl;
526 qctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
527 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &qctrl)) {
528 /* ... */
529 qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
530 }
531 </programlisting>
532 </informalexample>
534 <para>The initial control ID is set to 0 ORed with the
535 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag. The
536 <constant>VIDIOC_QUERYCTRL</constant> ioctl will return the first
537 control with a higher ID than the specified one. When no such controls
538 are found an error is returned.</para>
540 <para>If you want to get all controls within a specific control
541 class, then you can set the initial
542 <structfield>qctrl.id</structfield> value to the control class and add
543 an extra check to break out of the loop when a control of another
544 control class is found:</para>
546 <informalexample>
547 <programlisting>
548 qctrl.id = V4L2_CTRL_CLASS_MPEG | V4L2_CTRL_FLAG_NEXT_CTRL;
549 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &qctrl)) {
550 if (V4L2_CTRL_ID2CLASS (qctrl.id) != V4L2_CTRL_CLASS_MPEG)
551 break;
552 /* ... */
553 qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
554 }
555 </programlisting>
556 </informalexample>
558 <para>The 32-bit <structfield>qctrl.id</structfield> value is
559 subdivided into three bit ranges: the top 4 bits are reserved for
560 flags (⪚ <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>) and are not
561 actually part of the ID. The remaining 28 bits form the control ID, of
562 which the most significant 12 bits define the control class and the
563 least significant 16 bits identify the control within the control
564 class. It is guaranteed that these last 16 bits are always non-zero
565 for controls. The range of 0x1000 and up are reserved for
566 driver-specific controls. The macro
567 <constant>V4L2_CTRL_ID2CLASS(id)</constant> returns the control class
568 ID based on a control ID.</para>
570 <para>If the driver does not support extended controls, then
571 <constant>VIDIOC_QUERYCTRL</constant> will fail when used in
572 combination with <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>. In
573 that case the old method of enumerating control should be used (see
574 1.8). But if it is supported, then it is guaranteed to enumerate over
575 all controls, including driver-private controls.</para>
576 </section>
578 <section>
579 <title>Creating Control Panels</title>
581 <para>It is possible to create control panels for a graphical
582 user interface where the user can select the various controls.
583 Basically you will have to iterate over all controls using the method
584 described above. Each control class starts with a control of type
585 <constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant>.
586 <constant>VIDIOC_QUERYCTRL</constant> will return the name of this
587 control class which can be used as the title of a tab page within a
588 control panel.</para>
590 <para>The flags field of &v4l2-queryctrl; also contains hints on
591 the behavior of the control. See the &VIDIOC-QUERYCTRL; documentation
592 for more details.</para>
593 </section>
595 <section id="mpeg-controls">
596 <title>MPEG Control Reference</title>
598 <para>Below all controls within the MPEG control class are
599 described. First the generic controls, then controls specific for
600 certain hardware.</para>
602 <section>
603 <title>Generic MPEG Controls</title>
605 <table pgwide="1" frame="none" id="mpeg-control-id">
606 <title>MPEG Control IDs</title>
607 <tgroup cols="4">
608 <colspec colname="c1" colwidth="1*" />
609 <colspec colname="c2" colwidth="6*" />
610 <colspec colname="c3" colwidth="2*" />
611 <colspec colname="c4" colwidth="6*" />
612 <spanspec namest="c1" nameend="c2" spanname="id" />
613 <spanspec namest="c2" nameend="c4" spanname="descr" />
614 <thead>
615 <row>
616 <entry spanname="id" align="left">ID</entry>
617 <entry align="left">Type</entry>
618 </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
619 </row>
620 </thead>
621 <tbody valign="top">
622 <row><entry></entry></row>
623 <row>
624 <entry spanname="id"><constant>V4L2_CID_MPEG_CLASS</constant> </entry>
625 <entry>class</entry>
626 </row><row><entry spanname="descr">The MPEG class
627 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
628 description of this control class. This description can be used as the
629 caption of a Tab page in a GUI, for example.</entry>
630 </row>
631 <row><entry></entry></row>
632 <row id="v4l2-mpeg-stream-type">
633 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_TYPE</constant> </entry>
634 <entry>enum v4l2_mpeg_stream_type</entry>
635 </row><row><entry spanname="descr">The MPEG-1, -2 or -4
636 output stream type. One cannot assume anything here. Each hardware
637 MPEG encoder tends to support different subsets of the available MPEG
638 stream types. The currently defined stream types are:</entry>
639 </row>
640 <row>
641 <entrytbl spanname="descr" cols="2">
642 <tbody valign="top">
643 <row>
644 <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_PS</constant> </entry>
645 <entry>MPEG-2 program stream</entry>
646 </row>
647 <row>
648 <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_TS</constant> </entry>
649 <entry>MPEG-2 transport stream</entry>
650 </row>
651 <row>
652 <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_SS</constant> </entry>
653 <entry>MPEG-1 system stream</entry>
654 </row>
655 <row>
656 <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_DVD</constant> </entry>
657 <entry>MPEG-2 DVD-compatible stream</entry>
658 </row>
659 <row>
660 <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_VCD</constant> </entry>
661 <entry>MPEG-1 VCD-compatible stream</entry>
662 </row>
663 <row>
664 <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_SVCD</constant> </entry>
665 <entry>MPEG-2 SVCD-compatible stream</entry>
666 </row>
667 </tbody>
668 </entrytbl>
669 </row>
670 <row><entry></entry></row>
671 <row>
672 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PMT</constant> </entry>
673 <entry>integer</entry>
674 </row><row><entry spanname="descr">Program Map Table
675 Packet ID for the MPEG transport stream (default 16)</entry>
676 </row>
677 <row><entry></entry></row>
678 <row>
679 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_AUDIO</constant> </entry>
680 <entry>integer</entry>
681 </row><row><entry spanname="descr">Audio Packet ID for
682 the MPEG transport stream (default 256)</entry>
683 </row>
684 <row><entry></entry></row>
685 <row>
686 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_VIDEO</constant> </entry>
687 <entry>integer</entry>
688 </row><row><entry spanname="descr">Video Packet ID for
689 the MPEG transport stream (default 260)</entry>
690 </row>
691 <row><entry></entry></row>
692 <row>
693 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PCR</constant> </entry>
694 <entry>integer</entry>
695 </row><row><entry spanname="descr">Packet ID for the
696 MPEG transport stream carrying PCR fields (default 259)</entry>
697 </row>
698 <row><entry></entry></row>
699 <row>
700 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_AUDIO</constant> </entry>
701 <entry>integer</entry>
702 </row><row><entry spanname="descr">Audio ID for MPEG
703 PES</entry>
704 </row>
705 <row><entry></entry></row>
706 <row>
707 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_VIDEO</constant> </entry>
708 <entry>integer</entry>
709 </row><row><entry spanname="descr">Video ID for MPEG
710 PES</entry>
711 </row>
712 <row><entry></entry></row>
713 <row id="v4l2-mpeg-stream-vbi-fmt">
714 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_VBI_FMT</constant> </entry>
715 <entry>enum v4l2_mpeg_stream_vbi_fmt</entry>
716 </row><row><entry spanname="descr">Some cards can embed
717 VBI data (⪚ Closed Caption, Teletext) into the MPEG stream. This
718 control selects whether VBI data should be embedded, and if so, what
719 embedding method should be used. The list of possible VBI formats
720 depends on the driver. The currently defined VBI format types
721 are:</entry>
722 </row>
723 <row>
724 <entrytbl spanname="descr" cols="2">
725 <tbody valign="top">
726 <row>
727 <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_NONE</constant> </entry>
728 <entry>No VBI in the MPEG stream</entry>
729 </row>
730 <row>
731 <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant> </entry>
732 <entry>VBI in private packets, IVTV format (documented
733 in the kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.vbi</filename>)</entry>
734 </row>
735 </tbody>
736 </entrytbl>
737 </row>
738 <row><entry></entry></row>
739 <row id="v4l2-mpeg-audio-sampling-freq">
740 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ</constant> </entry>
741 <entry>enum v4l2_mpeg_audio_sampling_freq</entry>
742 </row><row><entry spanname="descr">MPEG Audio sampling
743 frequency. Possible values are:</entry>
744 </row>
745 <row>
746 <entrytbl spanname="descr" cols="2">
747 <tbody valign="top">
748 <row>
749 <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_44100</constant> </entry>
750 <entry>44.1 kHz</entry>
751 </row>
752 <row>
753 <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_48000</constant> </entry>
754 <entry>48 kHz</entry>
755 </row>
756 <row>
757 <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_32000</constant> </entry>
758 <entry>32 kHz</entry>
759 </row>
760 </tbody>
761 </entrytbl>
762 </row>
763 <row><entry></entry></row>
764 <row id="v4l2-mpeg-audio-encoding">
765 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_ENCODING</constant> </entry>
766 <entry>enum v4l2_mpeg_audio_encoding</entry>
767 </row><row><entry spanname="descr">MPEG Audio encoding.
768 Possible values are:</entry>
769 </row>
770 <row>
771 <entrytbl spanname="descr" cols="2">
772 <tbody valign="top">
773 <row>
774 <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_1</constant> </entry>
775 <entry>MPEG-1/2 Layer I encoding</entry>
776 </row>
777 <row>
778 <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_2</constant> </entry>
779 <entry>MPEG-1/2 Layer II encoding</entry>
780 </row>
781 <row>
782 <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_3</constant> </entry>
783 <entry>MPEG-1/2 Layer III encoding</entry>
784 </row>
785 <row>
786 <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant> </entry>
787 <entry>MPEG-2/4 AAC (Advanced Audio Coding)</entry>
788 </row>
789 <row>
790 <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant> </entry>
791 <entry>AC-3 aka ATSC A/52 encoding</entry>
792 </row>
793 </tbody>
794 </entrytbl>
795 </row>
796 <row><entry></entry></row>
797 <row id="v4l2-mpeg-audio-l1-bitrate">
798 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L1_BITRATE</constant> </entry>
799 <entry>enum v4l2_mpeg_audio_l1_bitrate</entry>
800 </row><row><entry spanname="descr">MPEG-1/2 Layer I bitrate.
801 Possible values are:</entry>
802 </row>
803 <row>
804 <entrytbl spanname="descr" cols="2">
805 <tbody valign="top">
806 <row>
807 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_32K</constant> </entry>
808 <entry>32 kbit/s</entry></row>
809 <row>
810 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_64K</constant> </entry>
811 <entry>64 kbit/s</entry>
812 </row>
813 <row>
814 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_96K</constant> </entry>
815 <entry>96 kbit/s</entry>
816 </row>
817 <row>
818 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_128K</constant> </entry>
819 <entry>128 kbit/s</entry>
820 </row>
821 <row>
822 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_160K</constant> </entry>
823 <entry>160 kbit/s</entry>
824 </row>
825 <row>
826 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_192K</constant> </entry>
827 <entry>192 kbit/s</entry>
828 </row>
829 <row>
830 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_224K</constant> </entry>
831 <entry>224 kbit/s</entry>
832 </row>
833 <row>
834 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_256K</constant> </entry>
835 <entry>256 kbit/s</entry>
836 </row>
837 <row>
838 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_288K</constant> </entry>
839 <entry>288 kbit/s</entry>
840 </row>
841 <row>
842 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_320K</constant> </entry>
843 <entry>320 kbit/s</entry>
844 </row>
845 <row>
846 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_352K</constant> </entry>
847 <entry>352 kbit/s</entry>
848 </row>
849 <row>
850 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_384K</constant> </entry>
851 <entry>384 kbit/s</entry>
852 </row>
853 <row>
854 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_416K</constant> </entry>
855 <entry>416 kbit/s</entry>
856 </row>
857 <row>
858 <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_448K</constant> </entry>
859 <entry>448 kbit/s</entry>
860 </row>
861 </tbody>
862 </entrytbl>
863 </row>
864 <row><entry></entry></row>
865 <row id="v4l2-mpeg-audio-l2-bitrate">
866 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L2_BITRATE</constant> </entry>
867 <entry>enum v4l2_mpeg_audio_l2_bitrate</entry>
868 </row><row><entry spanname="descr">MPEG-1/2 Layer II bitrate.
869 Possible values are:</entry>
870 </row>
871 <row>
872 <entrytbl spanname="descr" cols="2">
873 <tbody valign="top">
874 <row>
875 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_32K</constant> </entry>
876 <entry>32 kbit/s</entry>
877 </row>
878 <row>
879 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_48K</constant> </entry>
880 <entry>48 kbit/s</entry>
881 </row>
882 <row>
883 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_56K</constant> </entry>
884 <entry>56 kbit/s</entry>
885 </row>
886 <row>
887 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_64K</constant> </entry>
888 <entry>64 kbit/s</entry>
889 </row>
890 <row>
891 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_80K</constant> </entry>
892 <entry>80 kbit/s</entry>
893 </row>
894 <row>
895 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_96K</constant> </entry>
896 <entry>96 kbit/s</entry>
897 </row>
898 <row>
899 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_112K</constant> </entry>
900 <entry>112 kbit/s</entry>
901 </row>
902 <row>
903 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_128K</constant> </entry>
904 <entry>128 kbit/s</entry>
905 </row>
906 <row>
907 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_160K</constant> </entry>
908 <entry>160 kbit/s</entry>
909 </row>
910 <row>
911 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_192K</constant> </entry>
912 <entry>192 kbit/s</entry>
913 </row>
914 <row>
915 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_224K</constant> </entry>
916 <entry>224 kbit/s</entry>
917 </row>
918 <row>
919 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_256K</constant> </entry>
920 <entry>256 kbit/s</entry>
921 </row>
922 <row>
923 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_320K</constant> </entry>
924 <entry>320 kbit/s</entry>
925 </row>
926 <row>
927 <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_384K</constant> </entry>
928 <entry>384 kbit/s</entry>
929 </row>
930 </tbody>
931 </entrytbl>
932 </row>
933 <row><entry></entry></row>
934 <row id="v4l2-mpeg-audio-l3-bitrate">
935 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L3_BITRATE</constant> </entry>
936 <entry>enum v4l2_mpeg_audio_l3_bitrate</entry>
937 </row><row><entry spanname="descr">MPEG-1/2 Layer III bitrate.
938 Possible values are:</entry>
939 </row>
940 <row>
941 <entrytbl spanname="descr" cols="2">
942 <tbody valign="top">
943 <row>
944 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_32K</constant> </entry>
945 <entry>32 kbit/s</entry>
946 </row>
947 <row>
948 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_40K</constant> </entry>
949 <entry>40 kbit/s</entry>
950 </row>
951 <row>
952 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_48K</constant> </entry>
953 <entry>48 kbit/s</entry>
954 </row>
955 <row>
956 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_56K</constant> </entry>
957 <entry>56 kbit/s</entry>
958 </row>
959 <row>
960 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_64K</constant> </entry>
961 <entry>64 kbit/s</entry>
962 </row>
963 <row>
964 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_80K</constant> </entry>
965 <entry>80 kbit/s</entry>
966 </row>
967 <row>
968 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_96K</constant> </entry>
969 <entry>96 kbit/s</entry>
970 </row>
971 <row>
972 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_112K</constant> </entry>
973 <entry>112 kbit/s</entry>
974 </row>
975 <row>
976 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_128K</constant> </entry>
977 <entry>128 kbit/s</entry>
978 </row>
979 <row>
980 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_160K</constant> </entry>
981 <entry>160 kbit/s</entry>
982 </row>
983 <row>
984 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_192K</constant> </entry>
985 <entry>192 kbit/s</entry>
986 </row>
987 <row>
988 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_224K</constant> </entry>
989 <entry>224 kbit/s</entry>
990 </row>
991 <row>
992 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_256K</constant> </entry>
993 <entry>256 kbit/s</entry>
994 </row>
995 <row>
996 <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_320K</constant> </entry>
997 <entry>320 kbit/s</entry>
998 </row>
999 </tbody>
1000 </entrytbl>
1001 </row>
1002 <row><entry></entry></row>
1003 <row>
1004 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AAC_BITRATE</constant> </entry>
1005 <entry>integer</entry>
1006 </row><row><entry spanname="descr">AAC bitrate in bits per second.</entry>
1007 </row>
1008 <row><entry></entry></row>
1009 <row id="v4l2-mpeg-audio-ac3-bitrate">
1010 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AC3_BITRATE</constant> </entry>
1011 <entry>enum v4l2_mpeg_audio_ac3_bitrate</entry>
1012 </row><row><entry spanname="descr">AC-3 bitrate.
1013 Possible values are:</entry>
1014 </row>
1015 <row>
1016 <entrytbl spanname="descr" cols="2">
1017 <tbody valign="top">
1018 <row>
1019 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_32K</constant> </entry>
1020 <entry>32 kbit/s</entry>
1021 </row>
1022 <row>
1023 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_40K</constant> </entry>
1024 <entry>40 kbit/s</entry>
1025 </row>
1026 <row>
1027 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_48K</constant> </entry>
1028 <entry>48 kbit/s</entry>
1029 </row>
1030 <row>
1031 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_56K</constant> </entry>
1032 <entry>56 kbit/s</entry>
1033 </row>
1034 <row>
1035 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_64K</constant> </entry>
1036 <entry>64 kbit/s</entry>
1037 </row>
1038 <row>
1039 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_80K</constant> </entry>
1040 <entry>80 kbit/s</entry>
1041 </row>
1042 <row>
1043 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_96K</constant> </entry>
1044 <entry>96 kbit/s</entry>
1045 </row>
1046 <row>
1047 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_112K</constant> </entry>
1048 <entry>112 kbit/s</entry>
1049 </row>
1050 <row>
1051 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_128K</constant> </entry>
1052 <entry>128 kbit/s</entry>
1053 </row>
1054 <row>
1055 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_160K</constant> </entry>
1056 <entry>160 kbit/s</entry>
1057 </row>
1058 <row>
1059 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_192K</constant> </entry>
1060 <entry>192 kbit/s</entry>
1061 </row>
1062 <row>
1063 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_224K</constant> </entry>
1064 <entry>224 kbit/s</entry>
1065 </row>
1066 <row>
1067 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_256K</constant> </entry>
1068 <entry>256 kbit/s</entry>
1069 </row>
1070 <row>
1071 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_320K</constant> </entry>
1072 <entry>320 kbit/s</entry>
1073 </row>
1074 <row>
1075 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_384K</constant> </entry>
1076 <entry>384 kbit/s</entry>
1077 </row>
1078 <row>
1079 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_448K</constant> </entry>
1080 <entry>448 kbit/s</entry>
1081 </row>
1082 <row>
1083 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_512K</constant> </entry>
1084 <entry>512 kbit/s</entry>
1085 </row>
1086 <row>
1087 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_576K</constant> </entry>
1088 <entry>576 kbit/s</entry>
1089 </row>
1090 <row>
1091 <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_640K</constant> </entry>
1092 <entry>640 kbit/s</entry>
1093 </row>
1094 </tbody>
1095 </entrytbl>
1096 </row>
1097 <row><entry></entry></row>
1098 <row id="v4l2-mpeg-audio-mode">
1099 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE</constant> </entry>
1100 <entry>enum v4l2_mpeg_audio_mode</entry>
1101 </row><row><entry spanname="descr">MPEG Audio mode.
1102 Possible values are:</entry>
1103 </row>
1104 <row>
1105 <entrytbl spanname="descr" cols="2">
1106 <tbody valign="top">
1107 <row>
1108 <entry><constant>V4L2_MPEG_AUDIO_MODE_STEREO</constant> </entry>
1109 <entry>Stereo</entry>
1110 </row>
1111 <row>
1112 <entry><constant>V4L2_MPEG_AUDIO_MODE_JOINT_STEREO</constant> </entry>
1113 <entry>Joint Stereo</entry>
1114 </row>
1115 <row>
1116 <entry><constant>V4L2_MPEG_AUDIO_MODE_DUAL</constant> </entry>
1117 <entry>Bilingual</entry>
1118 </row>
1119 <row>
1120 <entry><constant>V4L2_MPEG_AUDIO_MODE_MONO</constant> </entry>
1121 <entry>Mono</entry>
1122 </row>
1123 </tbody>
1124 </entrytbl>
1125 </row>
1126 <row><entry></entry></row>
1127 <row id="v4l2-mpeg-audio-mode-extension">
1128 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE_EXTENSION</constant> </entry>
1129 <entry>enum v4l2_mpeg_audio_mode_extension</entry>
1130 </row><row><entry spanname="descr">Joint Stereo
1131 audio mode extension. In Layer I and II they indicate which subbands
1132 are in intensity stereo. All other subbands are coded in stereo. Layer
1133 III is not (yet) supported. Possible values
1134 are:</entry>
1135 </row>
1136 <row>
1137 <entrytbl spanname="descr" cols="2">
1138 <tbody valign="top">
1139 <row>
1140 <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_4</constant> </entry>
1141 <entry>Subbands 4-31 in intensity stereo</entry>
1142 </row>
1143 <row>
1144 <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_8</constant> </entry>
1145 <entry>Subbands 8-31 in intensity stereo</entry>
1146 </row>
1147 <row>
1148 <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_12</constant> </entry>
1149 <entry>Subbands 12-31 in intensity stereo</entry>
1150 </row>
1151 <row>
1152 <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_16</constant> </entry>
1153 <entry>Subbands 16-31 in intensity stereo</entry>
1154 </row>
1155 </tbody>
1156 </entrytbl>
1157 </row>
1158 <row><entry></entry></row>
1159 <row id="v4l2-mpeg-audio-emphasis">
1160 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_EMPHASIS</constant> </entry>
1161 <entry>enum v4l2_mpeg_audio_emphasis</entry>
1162 </row><row><entry spanname="descr">Audio Emphasis.
1163 Possible values are:</entry>
1164 </row>
1165 <row>
1166 <entrytbl spanname="descr" cols="2">
1167 <tbody valign="top">
1168 <row>
1169 <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_NONE</constant> </entry>
1170 <entry>None</entry>
1171 </row>
1172 <row>
1173 <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_50_DIV_15_uS</constant> </entry>
1174 <entry>50/15 microsecond emphasis</entry>
1175 </row>
1176 <row>
1177 <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_CCITT_J17</constant> </entry>
1178 <entry>CCITT J.17</entry>
1179 </row>
1180 </tbody>
1181 </entrytbl>
1182 </row>
1183 <row><entry></entry></row>
1184 <row id="v4l2-mpeg-audio-crc">
1185 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_CRC</constant> </entry>
1186 <entry>enum v4l2_mpeg_audio_crc</entry>
1187 </row><row><entry spanname="descr">CRC method. Possible
1188 values are:</entry>
1189 </row>
1190 <row>
1191 <entrytbl spanname="descr" cols="2">
1192 <tbody valign="top">
1193 <row>
1194 <entry><constant>V4L2_MPEG_AUDIO_CRC_NONE</constant> </entry>
1195 <entry>None</entry>
1196 </row>
1197 <row>
1198 <entry><constant>V4L2_MPEG_AUDIO_CRC_CRC16</constant> </entry>
1199 <entry>16 bit parity check</entry>
1200 </row>
1201 </tbody>
1202 </entrytbl>
1203 </row>
1204 <row><entry></entry></row>
1205 <row>
1206 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MUTE</constant> </entry>
1207 <entry>boolean</entry>
1208 </row><row><entry spanname="descr">Mutes the audio when
1209 capturing. This is not done by muting audio hardware, which can still
1210 produce a slight hiss, but in the encoder itself, guaranteeing a fixed
1211 and reproducable audio bitstream. 0 = unmuted, 1 = muted.</entry>
1212 </row>
1213 <row><entry></entry></row>
1214 <row id="v4l2-mpeg-video-encoding">
1215 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ENCODING</constant> </entry>
1216 <entry>enum v4l2_mpeg_video_encoding</entry>
1217 </row><row><entry spanname="descr">MPEG Video encoding
1218 method. Possible values are:</entry>
1219 </row>
1220 <row>
1221 <entrytbl spanname="descr" cols="2">
1222 <tbody valign="top">
1223 <row>
1224 <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_1</constant> </entry>
1225 <entry>MPEG-1 Video encoding</entry>
1226 </row>
1227 <row>
1228 <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_2</constant> </entry>
1229 <entry>MPEG-2 Video encoding</entry>
1230 </row>
1231 <row>
1232 <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant> </entry>
1233 <entry>MPEG-4 AVC (H.264) Video encoding</entry>
1234 </row>
1235 </tbody>
1236 </entrytbl>
1237 </row>
1238 <row><entry></entry></row>
1239 <row id="v4l2-mpeg-video-aspect">
1240 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ASPECT</constant> </entry>
1241 <entry>enum v4l2_mpeg_video_aspect</entry>
1242 </row><row><entry spanname="descr">Video aspect.
1243 Possible values are:</entry>
1244 </row>
1245 <row>
1246 <entrytbl spanname="descr" cols="2">
1247 <tbody valign="top">
1248 <row>
1249 <entry><constant>V4L2_MPEG_VIDEO_ASPECT_1x1</constant> </entry>
1250 </row>
1251 <row>
1252 <entry><constant>V4L2_MPEG_VIDEO_ASPECT_4x3</constant> </entry>
1253 </row>
1254 <row>
1255 <entry><constant>V4L2_MPEG_VIDEO_ASPECT_16x9</constant> </entry>
1256 </row>
1257 <row>
1258 <entry><constant>V4L2_MPEG_VIDEO_ASPECT_221x100</constant> </entry>
1259 </row>
1260 </tbody>
1261 </entrytbl>
1262 </row>
1263 <row><entry></entry></row>
1264 <row>
1265 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_B_FRAMES</constant> </entry>
1266 <entry>integer</entry>
1267 </row><row><entry spanname="descr">Number of B-Frames
1268 (default 2)</entry>
1269 </row>
1270 <row><entry></entry></row>
1271 <row>
1272 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_SIZE</constant> </entry>
1273 <entry>integer</entry>
1274 </row><row><entry spanname="descr">GOP size (default
1275 12)</entry>
1276 </row>
1277 <row><entry></entry></row>
1278 <row>
1279 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_CLOSURE</constant> </entry>
1280 <entry>boolean</entry>
1281 </row><row><entry spanname="descr">GOP closure (default
1282 1)</entry>
1283 </row>
1284 <row><entry></entry></row>
1285 <row>
1286 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_PULLDOWN</constant> </entry>
1287 <entry>boolean</entry>
1288 </row><row><entry spanname="descr">Enable 3:2 pulldown
1289 (default 0)</entry>
1290 </row>
1291 <row><entry></entry></row>
1292 <row id="v4l2-mpeg-video-bitrate-mode">
1293 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_MODE</constant> </entry>
1294 <entry>enum v4l2_mpeg_video_bitrate_mode</entry>
1295 </row><row><entry spanname="descr">Video bitrate mode.
1296 Possible values are:</entry>
1297 </row>
1298 <row>
1299 <entrytbl spanname="descr" cols="2">
1300 <tbody valign="top">
1301 <row>
1302 <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_VBR</constant> </entry>
1303 <entry>Variable bitrate</entry>
1304 </row>
1305 <row>
1306 <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_CBR</constant> </entry>
1307 <entry>Constant bitrate</entry>
1308 </row>
1309 </tbody>
1310 </entrytbl>
1311 </row>
1312 <row><entry></entry></row>
1313 <row>
1314 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE</constant> </entry>
1315 <entry>integer</entry>
1316 </row><row><entry spanname="descr">Video bitrate in bits
1317 per second.</entry>
1318 </row>
1319 <row><entry></entry></row>
1320 <row>
1321 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_PEAK</constant> </entry>
1322 <entry>integer</entry>
1323 </row><row><entry spanname="descr">Peak video bitrate in
1324 bits per second. Must be larger or equal to the average video bitrate.
1325 It is ignored if the video bitrate mode is set to constant
1326 bitrate.</entry>
1327 </row>
1328 <row><entry></entry></row>
1329 <row>
1330 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION</constant> </entry>
1331 <entry>integer</entry>
1332 </row><row><entry spanname="descr">For every captured
1333 frame, skip this many subsequent frames (default 0).</entry>
1334 </row>
1335 <row><entry></entry></row>
1336 <row>
1337 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE</constant> </entry>
1338 <entry>boolean</entry>
1339 </row>
1340 <row><entry spanname="descr">"Mutes" the video to a
1341 fixed color when capturing. This is useful for testing, to produce a
1342 fixed video bitstream. 0 = unmuted, 1 = muted.</entry>
1343 </row>
1344 <row><entry></entry></row>
1345 <row>
1346 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE_YUV</constant> </entry>
1347 <entry>integer</entry>
1348 </row><row><entry spanname="descr">Sets the "mute" color
1349 of the video. The supplied 32-bit integer is interpreted as follows (bit
1350 0 = least significant bit):</entry>
1351 </row>
1352 <row>
1353 <entrytbl spanname="descr" cols="2">
1354 <tbody valign="top">
1355 <row>
1356 <entry>Bit 0:7</entry>
1357 <entry>V chrominance information</entry>
1358 </row>
1359 <row>
1360 <entry>Bit 8:15</entry>
1361 <entry>U chrominance information</entry>
1362 </row>
1363 <row>
1364 <entry>Bit 16:23</entry>
1365 <entry>Y luminance information</entry>
1366 </row>
1367 <row>
1368 <entry>Bit 24:31</entry>
1369 <entry>Must be zero.</entry>
1370 </row>
1371 </tbody>
1372 </entrytbl>
1373 </row>
1374 </tbody>
1375 </tgroup>
1376 </table>
1377 </section>
1379 <section>
1380 <title>CX2341x MPEG Controls</title>
1382 <para>The following MPEG class controls deal with MPEG
1383 encoding settings that are specific to the Conexant CX23415 and
1384 CX23416 MPEG encoding chips.</para>
1386 <table pgwide="1" frame="none" id="cx2341x-control-id">
1387 <title>CX2341x Control IDs</title>
1388 <tgroup cols="4">
1389 <colspec colname="c1" colwidth="1*" />
1390 <colspec colname="c2" colwidth="6*" />
1391 <colspec colname="c3" colwidth="2*" />
1392 <colspec colname="c4" colwidth="6*" />
1393 <spanspec namest="c1" nameend="c2" spanname="id" />
1394 <spanspec namest="c2" nameend="c4" spanname="descr" />
1395 <thead>
1396 <row>
1397 <entry spanname="id" align="left">ID</entry>
1398 <entry align="left">Type</entry>
1399 </row><row><entry spanname="descr" align="left">Description</entry>
1400 </row>
1401 </thead>
1402 <tbody valign="top">
1403 <row><entry></entry></row>
1404 <row id="v4l2-mpeg-cx2341x-video-spatial-filter-mode">
1405 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE</constant> </entry>
1406 <entry>enum v4l2_mpeg_cx2341x_video_spatial_filter_mode</entry>
1407 </row><row><entry spanname="descr">Sets the Spatial
1408 Filter mode (default <constant>MANUAL</constant>). Possible values
1409 are:</entry>
1410 </row>
1411 <row>
1412 <entrytbl spanname="descr" cols="2">
1413 <tbody valign="top">
1414 <row>
1415 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_MANUAL</constant> </entry>
1416 <entry>Choose the filter manually</entry>
1417 </row>
1418 <row>
1419 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_AUTO</constant> </entry>
1420 <entry>Choose the filter automatically</entry>
1421 </row>
1422 </tbody>
1423 </entrytbl>
1424 </row>
1425 <row><entry></entry></row>
1426 <row>
1427 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER</constant> </entry>
1428 <entry>integer (0-15)</entry>
1429 </row><row><entry spanname="descr">The setting for the
1430 Spatial Filter. 0 = off, 15 = maximum. (Default is 0.)</entry>
1431 </row>
1432 <row><entry></entry></row>
1433 <row id="luma-spatial-filter-type">
1434 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE</constant> </entry>
1435 <entry>enum v4l2_mpeg_cx2341x_video_luma_spatial_filter_type</entry>
1436 </row><row><entry spanname="descr">Select the algorithm
1437 to use for the Luma Spatial Filter (default
1438 <constant>1D_HOR</constant>). Possible values:</entry>
1439 </row>
1440 <row>
1441 <entrytbl spanname="descr" cols="2">
1442 <tbody valign="top">
1443 <row>
1444 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_OFF</constant> </entry>
1445 <entry>No filter</entry>
1446 </row>
1447 <row>
1448 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_HOR</constant> </entry>
1449 <entry>One-dimensional horizontal</entry>
1450 </row>
1451 <row>
1452 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_VERT</constant> </entry>
1453 <entry>One-dimensional vertical</entry>
1454 </row>
1455 <row>
1456 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_HV_SEPARABLE</constant> </entry>
1457 <entry>Two-dimensional separable</entry>
1458 </row>
1459 <row>
1460 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_SYM_NON_SEPARABLE</constant> </entry>
1461 <entry>Two-dimensional symmetrical
1462 non-separable</entry>
1463 </row>
1464 </tbody>
1465 </entrytbl>
1466 </row>
1467 <row><entry></entry></row>
1468 <row id="chroma-spatial-filter-type">
1469 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE</constant> </entry>
1470 <entry>enum v4l2_mpeg_cx2341x_video_chroma_spatial_filter_type</entry>
1471 </row><row><entry spanname="descr">Select the algorithm
1472 for the Chroma Spatial Filter (default <constant>1D_HOR</constant>).
1473 Possible values are:</entry>
1474 </row>
1475 <row>
1476 <entrytbl spanname="descr" cols="2">
1477 <tbody valign="top">
1478 <row>
1479 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_OFF</constant> </entry>
1480 <entry>No filter</entry>
1481 </row>
1482 <row>
1483 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_1D_HOR</constant> </entry>
1484 <entry>One-dimensional horizontal</entry>
1485 </row>
1486 </tbody>
1487 </entrytbl>
1488 </row>
1489 <row><entry></entry></row>
1490 <row id="v4l2-mpeg-cx2341x-video-temporal-filter-mode">
1491 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE</constant> </entry>
1492 <entry>enum v4l2_mpeg_cx2341x_video_temporal_filter_mode</entry>
1493 </row><row><entry spanname="descr">Sets the Temporal
1494 Filter mode (default <constant>MANUAL</constant>). Possible values
1495 are:</entry>
1496 </row>
1497 <row>
1498 <entrytbl spanname="descr" cols="2">
1499 <tbody valign="top">
1500 <row>
1501 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_MANUAL</constant> </entry>
1502 <entry>Choose the filter manually</entry>
1503 </row>
1504 <row>
1505 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_AUTO</constant> </entry>
1506 <entry>Choose the filter automatically</entry>
1507 </row>
1508 </tbody>
1509 </entrytbl>
1510 </row>
1511 <row><entry></entry></row>
1512 <row>
1513 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER</constant> </entry>
1514 <entry>integer (0-31)</entry>
1515 </row><row><entry spanname="descr">The setting for the
1516 Temporal Filter. 0 = off, 31 = maximum. (Default is 8 for full-scale
1517 capturing and 0 for scaled capturing.)</entry>
1518 </row>
1519 <row><entry></entry></row>
1520 <row id="v4l2-mpeg-cx2341x-video-median-filter-type">
1521 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE</constant> </entry>
1522 <entry>enum v4l2_mpeg_cx2341x_video_median_filter_type</entry>
1523 </row><row><entry spanname="descr">Median Filter Type
1524 (default <constant>OFF</constant>). Possible values are:</entry>
1525 </row>
1526 <row>
1527 <entrytbl spanname="descr" cols="2">
1528 <tbody valign="top">
1529 <row>
1530 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_OFF</constant> </entry>
1531 <entry>No filter</entry>
1532 </row>
1533 <row>
1534 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR</constant> </entry>
1535 <entry>Horizontal filter</entry>
1536 </row>
1537 <row>
1538 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_VERT</constant> </entry>
1539 <entry>Vertical filter</entry>
1540 </row>
1541 <row>
1542 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR_VERT</constant> </entry>
1543 <entry>Horizontal and vertical filter</entry>
1544 </row>
1545 <row>
1546 <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_DIAG</constant> </entry>
1547 <entry>Diagonal filter</entry>
1548 </row>
1549 </tbody>
1550 </entrytbl>
1551 </row>
1552 <row><entry></entry></row>
1553 <row>
1554 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_BOTTOM</constant> </entry>
1555 <entry>integer (0-255)</entry>
1556 </row><row><entry spanname="descr">Threshold above which
1557 the luminance median filter is enabled (default 0)</entry>
1558 </row>
1559 <row><entry></entry></row>
1560 <row>
1561 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_TOP</constant> </entry>
1562 <entry>integer (0-255)</entry>
1563 </row><row><entry spanname="descr">Threshold below which
1564 the luminance median filter is enabled (default 255)</entry>
1565 </row>
1566 <row><entry></entry></row>
1567 <row>
1568 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_BOTTOM</constant> </entry>
1569 <entry>integer (0-255)</entry>
1570 </row><row><entry spanname="descr">Threshold above which
1571 the chroma median filter is enabled (default 0)</entry>
1572 </row>
1573 <row><entry></entry></row>
1574 <row>
1575 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_TOP</constant> </entry>
1576 <entry>integer (0-255)</entry>
1577 </row><row><entry spanname="descr">Threshold below which
1578 the chroma median filter is enabled (default 255)</entry>
1579 </row>
1580 <row><entry></entry></row>
1581 <row>
1582 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_STREAM_INSERT_NAV_PACKETS</constant> </entry>
1583 <entry>boolean</entry>
1584 </row>
1585 <row><entry spanname="descr">The CX2341X MPEG encoder
1586 can insert one empty MPEG-2 PES packet into the stream between every
1587 four video frames. The packet size is 2048 bytes, including the
1588 packet_start_code_prefix and stream_id fields. The stream_id is 0xBF
1589 (private stream 2). The payload consists of 0x00 bytes, to be filled
1590 in by the application. 0 = do not insert, 1 = insert packets.</entry>
1591 </row>
1592 </tbody>
1593 </tgroup>
1594 </table>
1595 </section>
1596 </section>
1598 <section id="camera-controls">
1599 <title>Camera Control Reference</title>
1601 <para>The Camera class includes controls for mechanical (or
1602 equivalent digital) features of a device such as controllable lenses
1603 or sensors.</para>
1605 <table pgwide="1" frame="none" id="camera-control-id">
1606 <title>Camera Control IDs</title>
1607 <tgroup cols="4">
1608 <colspec colname="c1" colwidth="1*" />
1609 <colspec colname="c2" colwidth="6*" />
1610 <colspec colname="c3" colwidth="2*" />
1611 <colspec colname="c4" colwidth="6*" />
1612 <spanspec namest="c1" nameend="c2" spanname="id" />
1613 <spanspec namest="c2" nameend="c4" spanname="descr" />
1614 <thead>
1615 <row>
1616 <entry spanname="id" align="left">ID</entry>
1617 <entry align="left">Type</entry>
1618 </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1619 </row>
1620 </thead>
1621 <tbody valign="top">
1622 <row><entry></entry></row>
1623 <row>
1624 <entry spanname="id"><constant>V4L2_CID_CAMERA_CLASS</constant> </entry>
1625 <entry>class</entry>
1626 </row><row><entry spanname="descr">The Camera class
1627 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1628 description of this control class.</entry>
1629 </row>
1630 <row><entry></entry></row>
1632 <row id="v4l2-exposure-auto-type">
1633 <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO</constant> </entry>
1634 <entry>enum v4l2_exposure_auto_type</entry>
1635 </row><row><entry spanname="descr">Enables automatic
1636 adjustments of the exposure time and/or iris aperture. The effect of
1637 manual changes of the exposure time or iris aperture while these
1638 features are enabled is undefined, drivers should ignore such
1639 requests. Possible values are:</entry>
1640 </row>
1641 <row>
1642 <entrytbl spanname="descr" cols="2">
1643 <tbody valign="top">
1644 <row>
1645 <entry><constant>V4L2_EXPOSURE_AUTO</constant> </entry>
1646 <entry>Automatic exposure time, automatic iris
1647 aperture.</entry>
1648 </row>
1649 <row>
1650 <entry><constant>V4L2_EXPOSURE_MANUAL</constant> </entry>
1651 <entry>Manual exposure time, manual iris.</entry>
1652 </row>
1653 <row>
1654 <entry><constant>V4L2_EXPOSURE_SHUTTER_PRIORITY</constant> </entry>
1655 <entry>Manual exposure time, auto iris.</entry>
1656 </row>
1657 <row>
1658 <entry><constant>V4L2_EXPOSURE_APERTURE_PRIORITY</constant> </entry>
1659 <entry>Auto exposure time, manual iris.</entry>
1660 </row>
1661 </tbody>
1662 </entrytbl>
1663 </row>
1664 <row><entry></entry></row>
1666 <row>
1667 <entry spanname="id"><constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant> </entry>
1668 <entry>integer</entry>
1669 </row><row><entry spanname="descr">Determines the exposure
1670 time of the camera sensor. The exposure time is limited by the frame
1671 interval. Drivers should interpret the values as 100 µs units,
1672 where the value 1 stands for 1/10000th of a second, 10000 for 1 second
1673 and 100000 for 10 seconds.</entry>
1674 </row>
1675 <row><entry></entry></row>
1677 <row>
1678 <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant> </entry>
1679 <entry>boolean</entry>
1680 </row><row><entry spanname="descr">When
1681 <constant>V4L2_CID_EXPOSURE_AUTO</constant> is set to
1682 <constant>AUTO</constant> or <constant>APERTURE_PRIORITY</constant>,
1683 this control determines if the device may dynamically vary the frame
1684 rate. By default this feature is disabled (0) and the frame rate must
1685 remain constant.</entry>
1686 </row>
1687 <row><entry></entry></row>
1689 <row>
1690 <entry spanname="id"><constant>V4L2_CID_PAN_RELATIVE</constant> </entry>
1691 <entry>integer</entry>
1692 </row><row><entry spanname="descr">This control turns the
1693 camera horizontally by the specified amount. The unit is undefined. A
1694 positive value moves the camera to the right (clockwise when viewed
1695 from above), a negative value to the left. A value of zero does not
1696 cause motion. This is a write-only control.</entry>
1697 </row>
1698 <row><entry></entry></row>
1700 <row>
1701 <entry spanname="id"><constant>V4L2_CID_TILT_RELATIVE</constant> </entry>
1702 <entry>integer</entry>
1703 </row><row><entry spanname="descr">This control turns the
1704 camera vertically by the specified amount. The unit is undefined. A
1705 positive value moves the camera up, a negative value down. A value of
1706 zero does not cause motion. This is a write-only control.</entry>
1707 </row>
1708 <row><entry></entry></row>
1710 <row>
1711 <entry spanname="id"><constant>V4L2_CID_PAN_RESET</constant> </entry>
1712 <entry>button</entry>
1713 </row><row><entry spanname="descr">When this control is set,
1714 the camera moves horizontally to the default position.</entry>
1715 </row>
1716 <row><entry></entry></row>
1718 <row>
1719 <entry spanname="id"><constant>V4L2_CID_TILT_RESET</constant> </entry>
1720 <entry>button</entry>
1721 </row><row><entry spanname="descr">When this control is set,
1722 the camera moves vertically to the default position.</entry>
1723 </row>
1724 <row><entry></entry></row>
1726 <row>
1727 <entry spanname="id"><constant>V4L2_CID_PAN_ABSOLUTE</constant> </entry>
1728 <entry>integer</entry>
1729 </row><row><entry spanname="descr">This control
1730 turns the camera horizontally to the specified position. Positive
1731 values move the camera to the right (clockwise when viewed from above),
1732 negative values to the left. Drivers should interpret the values as arc
1733 seconds, with valid values between -180 * 3600 and +180 * 3600
1734 inclusive.</entry>
1735 </row>
1736 <row><entry></entry></row>
1738 <row>
1739 <entry spanname="id"><constant>V4L2_CID_TILT_ABSOLUTE</constant> </entry>
1740 <entry>integer</entry>
1741 </row><row><entry spanname="descr">This control
1742 turns the camera vertically to the specified position. Positive values
1743 move the camera up, negative values down. Drivers should interpret the
1744 values as arc seconds, with valid values between -180 * 3600 and +180
1745 * 3600 inclusive.</entry>
1746 </row>
1747 <row><entry></entry></row>
1749 <row>
1750 <entry spanname="id"><constant>V4L2_CID_FOCUS_ABSOLUTE</constant> </entry>
1751 <entry>integer</entry>
1752 </row><row><entry spanname="descr">This control sets the
1753 focal point of the camera to the specified position. The unit is
1754 undefined. Positive values set the focus closer to the camera,
1755 negative values towards infinity.</entry>
1756 </row>
1757 <row><entry></entry></row>
1759 <row>
1760 <entry spanname="id"><constant>V4L2_CID_FOCUS_RELATIVE</constant> </entry>
1761 <entry>integer</entry>
1762 </row><row><entry spanname="descr">This control moves the
1763 focal point of the camera by the specified amount. The unit is
1764 undefined. Positive values move the focus closer to the camera,
1765 negative values towards infinity. This is a write-only control.</entry>
1766 </row>
1767 <row><entry></entry></row>
1769 <row>
1770 <entry spanname="id"><constant>V4L2_CID_FOCUS_AUTO</constant> </entry>
1771 <entry>boolean</entry>
1772 </row><row><entry spanname="descr">Enables automatic focus
1773 adjustments. The effect of manual focus adjustments while this feature
1774 is enabled is undefined, drivers should ignore such requests.</entry>
1775 </row>
1776 <row><entry></entry></row>
1778 <row>
1779 <entry spanname="id"><constant>V4L2_CID_ZOOM_ABSOLUTE</constant> </entry>
1780 <entry>integer</entry>
1781 </row><row><entry spanname="descr">Specify the objective lens
1782 focal length as an absolute value. The zoom unit is driver-specific and its
1783 value should be a positive integer.</entry>
1784 </row>
1785 <row><entry></entry></row>
1787 <row>
1788 <entry spanname="id"><constant>V4L2_CID_ZOOM_RELATIVE</constant> </entry>
1789 <entry>integer</entry>
1790 </row><row><entry spanname="descr">Specify the objective lens
1791 focal length relatively to the current value. Positive values move the zoom
1792 lens group towards the telephoto direction, negative values towards the
1793 wide-angle direction. The zoom unit is driver-specific. This is a write-only control.</entry>
1794 </row>
1795 <row><entry></entry></row>
1797 <row>
1798 <entry spanname="id"><constant>V4L2_CID_ZOOM_CONTINUOUS</constant> </entry>
1799 <entry>integer</entry>
1800 </row><row><entry spanname="descr">Move the objective lens group
1801 at the specified speed until it reaches physical device limits or until an
1802 explicit request to stop the movement. A positive value moves the zoom lens
1803 group towards the telephoto direction. A value of zero stops the zoom lens
1804 group movement. A negative value moves the zoom lens group towards the
1805 wide-angle direction. The zoom speed unit is driver-specific.</entry>
1806 </row>
1807 <row><entry></entry></row>
1809 <row>
1810 <entry spanname="id"><constant>V4L2_CID_PRIVACY</constant> </entry>
1811 <entry>boolean</entry>
1812 </row><row><entry spanname="descr">Prevent video from being acquired
1813 by the camera. When this control is set to <constant>TRUE</constant> (1), no
1814 image can be captured by the camera. Common means to enforce privacy are
1815 mechanical obturation of the sensor and firmware image processing, but the
1816 device is not restricted to these methods. Devices that implement the privacy
1817 control must support read access and may support write access.</entry>
1818 </row>
1820 <row>
1821 <entry spanname="id"><constant>V4L2_CID_BAND_STOP_FILTER</constant> </entry>
1822 <entry>integer</entry>
1823 </row><row><entry spanname="descr">Switch the band-stop filter of a
1824 camera sensor on or off, or specify its strength. Such band-stop filters can
1825 be used, for example, to filter out the fluorescent light component.</entry>
1826 </row>
1827 <row><entry></entry></row>
1828 </tbody>
1829 </tgroup>
1830 </table>
1831 </section>
1833 <section id="fm-tx-controls">
1834 <title>FM Transmitter Control Reference</title>
1836 <para>The FM Transmitter (FM_TX) class includes controls for common features of
1837 FM transmissions capable devices. Currently this class includes parameters for audio
1838 compression, pilot tone generation, audio deviation limiter, RDS transmission and
1839 tuning power features.</para>
1841 <table pgwide="1" frame="none" id="fm-tx-control-id">
1842 <title>FM_TX Control IDs</title>
1844 <tgroup cols="4">
1845 <colspec colname="c1" colwidth="1*" />
1846 <colspec colname="c2" colwidth="6*" />
1847 <colspec colname="c3" colwidth="2*" />
1848 <colspec colname="c4" colwidth="6*" />
1849 <spanspec namest="c1" nameend="c2" spanname="id" />
1850 <spanspec namest="c2" nameend="c4" spanname="descr" />
1851 <thead>
1852 <row>
1853 <entry spanname="id" align="left">ID</entry>
1854 <entry align="left">Type</entry>
1855 </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1856 </row>
1857 </thead>
1858 <tbody valign="top">
1859 <row><entry></entry></row>
1860 <row>
1861 <entry spanname="id"><constant>V4L2_CID_FM_TX_CLASS</constant> </entry>
1862 <entry>class</entry>
1863 </row><row><entry spanname="descr">The FM_TX class
1864 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1865 description of this control class.</entry>
1866 </row>
1867 <row>
1868 <entry spanname="id"><constant>V4L2_CID_RDS_TX_DEVIATION</constant> </entry>
1869 <entry>integer</entry>
1870 </row>
1871 <row><entry spanname="descr">Configures RDS signal frequency deviation level in Hz.
1872 The range and step are driver-specific.</entry>
1873 </row>
1874 <row>
1875 <entry spanname="id"><constant>V4L2_CID_RDS_TX_PI</constant> </entry>
1876 <entry>integer</entry>
1877 </row>
1878 <row><entry spanname="descr">Sets the RDS Programme Identification field
1879 for transmission.</entry>
1880 </row>
1881 <row>
1882 <entry spanname="id"><constant>V4L2_CID_RDS_TX_PTY</constant> </entry>
1883 <entry>integer</entry>
1884 </row>
1885 <row><entry spanname="descr">Sets the RDS Programme Type field for transmission.
1886 This encodes up to 31 pre-defined programme types.</entry>
1887 </row>
1888 <row>
1889 <entry spanname="id"><constant>V4L2_CID_RDS_TX_PS_NAME</constant> </entry>
1890 <entry>string</entry>
1891 </row>
1892 <row><entry spanname="descr">Sets the Programme Service name (PS_NAME) for transmission.
1893 It is intended for static display on a receiver. It is the primary aid to listeners in programme service
1894 identification and selection. In Annex E of <xref linkend="en50067" />, the RDS specification,
1895 there is a full description of the correct character encoding for Programme Service name strings.
1896 Also from RDS specification, PS is usually a single eight character text. However, it is also possible
1897 to find receivers which can scroll strings sized as 8 x N characters. So, this control must be configured
1898 with steps of 8 characters. The result is it must always contain a string with size multiple of 8.</entry>
1899 </row>
1900 <row>
1901 <entry spanname="id"><constant>V4L2_CID_RDS_TX_RADIO_TEXT</constant> </entry>
1902 <entry>string</entry>
1903 </row>
1904 <row><entry spanname="descr">Sets the Radio Text info for transmission. It is a textual description of
1905 what is being broadcasted. RDS Radio Text can be applied when broadcaster wishes to transmit longer PS names,
1906 programme-related information or any other text. In these cases, RadioText should be used in addition to
1907 <constant>V4L2_CID_RDS_TX_PS_NAME</constant>. The encoding for Radio Text strings is also fully described
1908 in Annex E of <xref linkend="en50067" />. The length of Radio Text strings depends on which RDS Block is being
1909 used to transmit it, either 32 (2A block) or 64 (2B block). However, it is also possible
1910 to find receivers which can scroll strings sized as 32 x N or 64 x N characters. So, this control must be configured
1911 with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. </entry>
1912 </row>
1913 <row>
1914 <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_ENABLED</constant> </entry>
1915 <entry>boolean</entry>
1916 </row>
1917 <row><entry spanname="descr">Enables or disables the audio deviation limiter feature.
1918 The limiter is useful when trying to maximize the audio volume, minimize receiver-generated
1919 distortion and prevent overmodulation.
1920 </entry>
1921 </row>
1922 <row>
1923 <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_RELEASE_TIME</constant> </entry>
1924 <entry>integer</entry>
1925 </row>
1926 <row><entry spanname="descr">Sets the audio deviation limiter feature release time.
1927 Unit is in useconds. Step and range are driver-specific.</entry>
1928 </row>
1929 <row>
1930 <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_DEVIATION</constant> </entry>
1931 <entry>integer</entry>
1932 </row>
1933 <row><entry spanname="descr">Configures audio frequency deviation level in Hz.
1934 The range and step are driver-specific.</entry>
1935 </row>
1936 <row>
1937 <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ENABLED</constant> </entry>
1938 <entry>boolean</entry>
1939 </row>
1940 <row><entry spanname="descr">Enables or disables the audio compression feature.
1941 This feature amplifies signals below the threshold by a fixed gain and compresses audio
1942 signals above the threshold by the ratio of Threshold/(Gain + Threshold).</entry>
1943 </row>
1944 <row>
1945 <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_GAIN</constant> </entry>
1946 <entry>integer</entry>
1947 </row>
1948 <row><entry spanname="descr">Sets the gain for audio compression feature. It is
1949 a dB value. The range and step are driver-specific.</entry>
1950 </row>
1951 <row>
1952 <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_THRESHOLD</constant> </entry>
1953 <entry>integer</entry>
1954 </row>
1955 <row><entry spanname="descr">Sets the threshold level for audio compression freature.
1956 It is a dB value. The range and step are driver-specific.</entry>
1957 </row>
1958 <row>
1959 <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME</constant> </entry>
1960 <entry>integer</entry>
1961 </row>
1962 <row><entry spanname="descr">Sets the attack time for audio compression feature.
1963 It is a useconds value. The range and step are driver-specific.</entry>
1964 </row>
1965 <row>
1966 <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME</constant> </entry>
1967 <entry>integer</entry>
1968 </row>
1969 <row><entry spanname="descr">Sets the release time for audio compression feature.
1970 It is a useconds value. The range and step are driver-specific.</entry>
1971 </row>
1972 <row>
1973 <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_ENABLED</constant> </entry>
1974 <entry>boolean</entry>
1975 </row>
1976 <row><entry spanname="descr">Enables or disables the pilot tone generation feature.</entry>
1977 </row>
1978 <row>
1979 <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_DEVIATION</constant> </entry>
1980 <entry>integer</entry>
1981 </row>
1982 <row><entry spanname="descr">Configures pilot tone frequency deviation level. Unit is
1983 in Hz. The range and step are driver-specific.</entry>
1984 </row>
1985 <row>
1986 <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_FREQUENCY</constant> </entry>
1987 <entry>integer</entry>
1988 </row>
1989 <row><entry spanname="descr">Configures pilot tone frequency value. Unit is
1990 in Hz. The range and step are driver-specific.</entry>
1991 </row>
1992 <row>
1993 <entry spanname="id"><constant>V4L2_CID_TUNE_PREEMPHASIS</constant> </entry>
1994 <entry>integer</entry>
1995 </row>
1996 <row id="v4l2-preemphasis"><entry spanname="descr">Configures the pre-emphasis value for broadcasting.
1997 A pre-emphasis filter is applied to the broadcast to accentuate the high audio frequencies.
1998 Depending on the region, a time constant of either 50 or 75 useconds is used. The enum v4l2_preemphasis
1999 defines possible values for pre-emphasis. Here they are:</entry>
2000 </row><row>
2001 <entrytbl spanname="descr" cols="2">
2002 <tbody valign="top">
2003 <row>
2004 <entry><constant>V4L2_PREEMPHASIS_DISABLED</constant> </entry>
2005 <entry>No pre-emphasis is applied.</entry>
2006 </row>
2007 <row>
2008 <entry><constant>V4L2_PREEMPHASIS_50_uS</constant> </entry>
2009 <entry>A pre-emphasis of 50 uS is used.</entry>
2010 </row>
2011 <row>
2012 <entry><constant>V4L2_PREEMPHASIS_75_uS</constant> </entry>
2013 <entry>A pre-emphasis of 75 uS is used.</entry>
2014 </row>
2015 </tbody>
2016 </entrytbl>
2018 </row>
2019 <row>
2020 <entry spanname="id"><constant>V4L2_CID_TUNE_POWER_LEVEL</constant> </entry>
2021 <entry>integer</entry>
2022 </row>
2023 <row><entry spanname="descr">Sets the output power level for signal transmission.
2024 Unit is in dBuV. Range and step are driver-specific.</entry>
2025 </row>
2026 <row>
2027 <entry spanname="id"><constant>V4L2_CID_TUNE_ANTENNA_CAPACITOR</constant> </entry>
2028 <entry>integer</entry>
2029 </row>
2030 <row><entry spanname="descr">This selects the value of antenna tuning capacitor
2031 manually or automatically if set to zero. Unit, range and step are driver-specific.</entry>
2032 </row>
2033 <row><entry></entry></row>
2034 </tbody>
2035 </tgroup>
2036 </table>
2038 <para>For more details about RDS specification, refer to
2039 <xref linkend="en50067" /> document, from CENELEC.</para>
2040 </section>
2041 </section>
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