3 <para>The following chapters document the evolution of the V4L2 API,
4 errata or extensions. They are also intended to help application and
5 driver writers to port or update their code.</para>
7 <section id="diff-v4l">
8 <title>Differences between V4L and V4L2</title>
10 <para>The Video For Linux API was first introduced in Linux 2.1 to
11 unify and replace various TV and radio device related interfaces,
12 developed independently by driver writers in prior years. Starting
13 with Linux 2.5 the much improved V4L2 API replaces the V4L API,
14 although existing drivers will continue to support V4L applications in
15 the future, either directly or through the V4L2 compatibility layer in
16 the <filename>videodev</filename> kernel module translating ioctls on
17 the fly. For a transition period not all drivers will support the V4L2
21 <title>Opening and Closing Devices</title>
23 <para>For compatibility reasons the character device file names
24 recommended for V4L2 video capture, overlay, radio and raw
25 vbi capture devices did not change from those used by V4L. They are
26 listed in <xref linkend="devices" /> and below in <xref
27 linkend="v4l-dev" />.</para>
29 <para>The teletext devices (minor range 192-223) have been removed in
30 V4L2 and no longer exist. There is no hardware available anymore for handling
31 pure teletext. Instead raw or sliced VBI is used.</para>
33 <para>The V4L <filename>videodev</filename> module automatically
34 assigns minor numbers to drivers in load order, depending on the
35 registered device type. We recommend that V4L2 drivers by default
36 register devices with the same numbers, but the system administrator
37 can assign arbitrary minor numbers using driver module options. The
38 major device number remains 81.</para>
41 <title>V4L Device Types, Names and Numbers</title>
45 <entry>Device Type</entry>
46 <entry>File Name</entry>
47 <entry>Minor Numbers</entry>
52 <entry>Video capture and overlay</entry>
53 <entry><para><filename>/dev/video</filename> and
54 <filename>/dev/bttv0</filename><footnote> <para>According to
55 Documentation/devices.txt these should be symbolic links to
56 <filename>/dev/video0</filename>. Note the original bttv interface is
57 not compatible with V4L or V4L2.</para> </footnote>,
58 <filename>/dev/video0</filename> to
59 <filename>/dev/video63</filename></para></entry>
63 <entry>Radio receiver</entry>
64 <entry><para><filename>/dev/radio</filename><footnote>
66 <filename>Documentation/devices.txt</filename> a symbolic link to
67 <filename>/dev/radio0</filename>.</para>
68 </footnote>, <filename>/dev/radio0</filename> to
69 <filename>/dev/radio63</filename></para></entry>
73 <entry>Raw VBI capture</entry>
74 <entry><para><filename>/dev/vbi</filename>,
75 <filename>/dev/vbi0</filename> to
76 <filename>/dev/vbi31</filename></para></entry>
77 <entry>224-255</entry>
83 <para>V4L prohibits (or used to prohibit) multiple opens of a
84 device file. V4L2 drivers <emphasis>may</emphasis> support multiple
85 opens, see <xref linkend="open" /> for details and consequences.</para>
87 <para>V4L drivers respond to V4L2 ioctls with an &EINVAL;. The
88 compatibility layer in the V4L2 <filename>videodev</filename> module
89 can translate V4L ioctl requests to their V4L2 counterpart, however a
90 V4L2 driver usually needs more preparation to become fully V4L
91 compatible. This is covered in more detail in <xref
92 linkend="driver" />.</para>
96 <title>Querying Capabilities</title>
98 <para>The V4L <constant>VIDIOCGCAP</constant> ioctl is
99 equivalent to V4L2's &VIDIOC-QUERYCAP;.</para>
101 <para>The <structfield>name</structfield> field in struct
102 <structname>video_capability</structname> became
103 <structfield>card</structfield> in &v4l2-capability;,
104 <structfield>type</structfield> was replaced by
105 <structfield>capabilities</structfield>. Note V4L2 does not
106 distinguish between device types like this, better think of basic
107 video input, video output and radio devices supporting a set of
108 related functions like video capturing, video overlay and VBI
109 capturing. See <xref linkend="open" /> for an
110 introduction.<informaltable>
115 <structname>video_capability</structname>
116 <structfield>type</structfield></entry>
117 <entry>&v4l2-capability;
118 <structfield>capabilities</structfield> flags</entry>
119 <entry>Purpose</entry>
124 <entry><constant>VID_TYPE_CAPTURE</constant></entry>
125 <entry><constant>V4L2_CAP_VIDEO_CAPTURE</constant></entry>
126 <entry>The <link linkend="capture">video
127 capture</link> interface is supported.</entry>
130 <entry><constant>VID_TYPE_TUNER</constant></entry>
131 <entry><constant>V4L2_CAP_TUNER</constant></entry>
132 <entry>The device has a <link linkend="tuner">tuner or
133 modulator</link>.</entry>
136 <entry><constant>VID_TYPE_TELETEXT</constant></entry>
137 <entry><constant>V4L2_CAP_VBI_CAPTURE</constant></entry>
138 <entry>The <link linkend="raw-vbi">raw VBI
139 capture</link> interface is supported.</entry>
142 <entry><constant>VID_TYPE_OVERLAY</constant></entry>
143 <entry><constant>V4L2_CAP_VIDEO_OVERLAY</constant></entry>
144 <entry>The <link linkend="overlay">video
145 overlay</link> interface is supported.</entry>
148 <entry><constant>VID_TYPE_CHROMAKEY</constant></entry>
149 <entry><constant>V4L2_FBUF_CAP_CHROMAKEY</constant> in
150 field <structfield>capability</structfield> of
151 &v4l2-framebuffer;</entry>
152 <entry>Whether chromakey overlay is supported. For
153 more information on overlay see
154 <xref linkend="overlay" />.</entry>
157 <entry><constant>VID_TYPE_CLIPPING</constant></entry>
158 <entry><constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant>
159 and <constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant> in field
160 <structfield>capability</structfield> of &v4l2-framebuffer;</entry>
161 <entry>Whether clipping the overlaid image is
162 supported, see <xref linkend="overlay" />.</entry>
165 <entry><constant>VID_TYPE_FRAMERAM</constant></entry>
166 <entry><constant>V4L2_FBUF_CAP_EXTERNOVERLAY</constant>
167 <emphasis>not set</emphasis> in field
168 <structfield>capability</structfield> of &v4l2-framebuffer;</entry>
169 <entry>Whether overlay overwrites frame buffer memory,
170 see <xref linkend="overlay" />.</entry>
173 <entry><constant>VID_TYPE_SCALES</constant></entry>
174 <entry><constant>-</constant></entry>
175 <entry>This flag indicates if the hardware can scale
176 images. The V4L2 API implies the scale factor by setting the cropping
177 dimensions and image size with the &VIDIOC-S-CROP; and &VIDIOC-S-FMT;
178 ioctl, respectively. The driver returns the closest sizes possible.
179 For more information on cropping and scaling see <xref
180 linkend="crop" />.</entry>
183 <entry><constant>VID_TYPE_MONOCHROME</constant></entry>
184 <entry><constant>-</constant></entry>
185 <entry>Applications can enumerate the supported image
186 formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device
187 supports grey scale capturing only. For more information on image
188 formats see <xref linkend="pixfmt" />.</entry>
191 <entry><constant>VID_TYPE_SUBCAPTURE</constant></entry>
192 <entry><constant>-</constant></entry>
193 <entry>Applications can call the &VIDIOC-G-CROP; ioctl
194 to determine if the device supports capturing a subsection of the full
195 picture ("cropping" in V4L2). If not, the ioctl returns the &EINVAL;.
196 For more information on cropping and scaling see <xref
197 linkend="crop" />.</entry>
200 <entry><constant>VID_TYPE_MPEG_DECODER</constant></entry>
201 <entry><constant>-</constant></entry>
202 <entry>Applications can enumerate the supported image
203 formats with the &VIDIOC-ENUM-FMT; ioctl to determine if the device
204 supports MPEG streams.</entry>
207 <entry><constant>VID_TYPE_MPEG_ENCODER</constant></entry>
208 <entry><constant>-</constant></entry>
209 <entry>See above.</entry>
212 <entry><constant>VID_TYPE_MJPEG_DECODER</constant></entry>
213 <entry><constant>-</constant></entry>
214 <entry>See above.</entry>
217 <entry><constant>VID_TYPE_MJPEG_ENCODER</constant></entry>
218 <entry><constant>-</constant></entry>
219 <entry>See above.</entry>
223 </informaltable></para>
225 <para>The <structfield>audios</structfield> field was replaced
226 by <structfield>capabilities</structfield> flag
227 <constant>V4L2_CAP_AUDIO</constant>, indicating
228 <emphasis>if</emphasis> the device has any audio inputs or outputs. To
229 determine their number applications can enumerate audio inputs with
230 the &VIDIOC-G-AUDIO; ioctl. The audio ioctls are described in <xref
231 linkend="audio" />.</para>
233 <para>The <structfield>maxwidth</structfield>,
234 <structfield>maxheight</structfield>,
235 <structfield>minwidth</structfield> and
236 <structfield>minheight</structfield> fields were removed. Calling the
237 &VIDIOC-S-FMT; or &VIDIOC-TRY-FMT; ioctl with the desired dimensions
238 returns the closest size possible, taking into account the current
239 video standard, cropping and scaling limitations.</para>
243 <title>Video Sources</title>
245 <para>V4L provides the <constant>VIDIOCGCHAN</constant> and
246 <constant>VIDIOCSCHAN</constant> ioctl using struct
247 <structname>video_channel</structname> to enumerate
248 the video inputs of a V4L device. The equivalent V4L2 ioctls
249 are &VIDIOC-ENUMINPUT;, &VIDIOC-G-INPUT; and &VIDIOC-S-INPUT;
250 using &v4l2-input; as discussed in <xref linkend="video" />.</para>
252 <para>The <structfield>channel</structfield> field counting
253 inputs was renamed to <structfield>index</structfield>, the video
254 input types were renamed as follows: <informaltable>
258 <entry>struct <structname>video_channel</structname>
259 <structfield>type</structfield></entry>
261 <structfield>type</structfield></entry>
266 <entry><constant>VIDEO_TYPE_TV</constant></entry>
267 <entry><constant>V4L2_INPUT_TYPE_TUNER</constant></entry>
270 <entry><constant>VIDEO_TYPE_CAMERA</constant></entry>
271 <entry><constant>V4L2_INPUT_TYPE_CAMERA</constant></entry>
275 </informaltable></para>
277 <para>Unlike the <structfield>tuners</structfield> field
278 expressing the number of tuners of this input, V4L2 assumes each video
279 input is connected to at most one tuner. However a tuner can have more
280 than one input, &ie; RF connectors, and a device can have multiple
281 tuners. The index number of the tuner associated with the input, if
282 any, is stored in field <structfield>tuner</structfield> of
283 &v4l2-input;. Enumeration of tuners is discussed in <xref
284 linkend="tuner" />.</para>
286 <para>The redundant <constant>VIDEO_VC_TUNER</constant> flag was
287 dropped. Video inputs associated with a tuner are of type
288 <constant>V4L2_INPUT_TYPE_TUNER</constant>. The
289 <constant>VIDEO_VC_AUDIO</constant> flag was replaced by the
290 <structfield>audioset</structfield> field. V4L2 considers devices with
291 up to 32 audio inputs. Each set bit in the
292 <structfield>audioset</structfield> field represents one audio input
293 this video input combines with. For information about audio inputs and
294 how to switch between them see <xref linkend="audio" />.</para>
296 <para>The <structfield>norm</structfield> field describing the
297 supported video standards was replaced by
298 <structfield>std</structfield>. The V4L specification mentions a flag
299 <constant>VIDEO_VC_NORM</constant> indicating whether the standard can
300 be changed. This flag was a later addition together with the
301 <structfield>norm</structfield> field and has been removed in the
302 meantime. V4L2 has a similar, albeit more comprehensive approach
303 to video standards, see <xref linkend="standard" /> for more
308 <title>Tuning</title>
310 <para>The V4L <constant>VIDIOCGTUNER</constant> and
311 <constant>VIDIOCSTUNER</constant> ioctl and struct
312 <structname>video_tuner</structname> can be used to enumerate the
313 tuners of a V4L TV or radio device. The equivalent V4L2 ioctls are
314 &VIDIOC-G-TUNER; and &VIDIOC-S-TUNER; using &v4l2-tuner;. Tuners are
315 covered in <xref linkend="tuner" />.</para>
317 <para>The <structfield>tuner</structfield> field counting tuners
318 was renamed to <structfield>index</structfield>. The fields
319 <structfield>name</structfield>, <structfield>rangelow</structfield>
320 and <structfield>rangehigh</structfield> remained unchanged.</para>
322 <para>The <constant>VIDEO_TUNER_PAL</constant>,
323 <constant>VIDEO_TUNER_NTSC</constant> and
324 <constant>VIDEO_TUNER_SECAM</constant> flags indicating the supported
325 video standards were dropped. This information is now contained in the
326 associated &v4l2-input;. No replacement exists for the
327 <constant>VIDEO_TUNER_NORM</constant> flag indicating whether the
328 video standard can be switched. The <structfield>mode</structfield>
329 field to select a different video standard was replaced by a whole new
330 set of ioctls and structures described in <xref linkend="standard" />.
331 Due to its ubiquity it should be mentioned the BTTV driver supports
332 several standards in addition to the regular
333 <constant>VIDEO_MODE_PAL</constant> (0),
334 <constant>VIDEO_MODE_NTSC</constant>,
335 <constant>VIDEO_MODE_SECAM</constant> and
336 <constant>VIDEO_MODE_AUTO</constant> (3). Namely N/PAL Argentina,
337 M/PAL, N/PAL, and NTSC Japan with numbers 3-6 (sic).</para>
339 <para>The <constant>VIDEO_TUNER_STEREO_ON</constant> flag
340 indicating stereo reception became
341 <constant>V4L2_TUNER_SUB_STEREO</constant> in field
342 <structfield>rxsubchans</structfield>. This field also permits the
343 detection of monaural and bilingual audio, see the definition of
344 &v4l2-tuner; for details. Presently no replacement exists for the
345 <constant>VIDEO_TUNER_RDS_ON</constant> and
346 <constant>VIDEO_TUNER_MBS_ON</constant> flags.</para>
348 <para> The <constant>VIDEO_TUNER_LOW</constant> flag was renamed
349 to <constant>V4L2_TUNER_CAP_LOW</constant> in the &v4l2-tuner;
350 <structfield>capability</structfield> field.</para>
352 <para>The <constant>VIDIOCGFREQ</constant> and
353 <constant>VIDIOCSFREQ</constant> ioctl to change the tuner frequency
354 where renamed to &VIDIOC-G-FREQUENCY; and &VIDIOC-S-FREQUENCY;. They
355 take a pointer to a &v4l2-frequency; instead of an unsigned long
359 <section id="v4l-image-properties">
360 <title>Image Properties</title>
362 <para>V4L2 has no equivalent of the
363 <constant>VIDIOCGPICT</constant> and <constant>VIDIOCSPICT</constant>
364 ioctl and struct <structname>video_picture</structname>. The following
365 fields where replaced by V4L2 controls accessible with the
366 &VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls:<informaltable>
370 <entry>struct <structname>video_picture</structname></entry>
371 <entry>V4L2 Control ID</entry>
376 <entry><structfield>brightness</structfield></entry>
377 <entry><constant>V4L2_CID_BRIGHTNESS</constant></entry>
380 <entry><structfield>hue</structfield></entry>
381 <entry><constant>V4L2_CID_HUE</constant></entry>
384 <entry><structfield>colour</structfield></entry>
385 <entry><constant>V4L2_CID_SATURATION</constant></entry>
388 <entry><structfield>contrast</structfield></entry>
389 <entry><constant>V4L2_CID_CONTRAST</constant></entry>
392 <entry><structfield>whiteness</structfield></entry>
393 <entry><constant>V4L2_CID_WHITENESS</constant></entry>
397 </informaltable></para>
399 <para>The V4L picture controls are assumed to range from 0 to
400 65535 with no particular reset value. The V4L2 API permits arbitrary
401 limits and defaults which can be queried with the &VIDIOC-QUERYCTRL;
402 ioctl. For general information about controls see <xref
403 linkend="control" />.</para>
405 <para>The <structfield>depth</structfield> (average number of
406 bits per pixel) of a video image is implied by the selected image
407 format. V4L2 does not explicitely provide such information assuming
408 applications recognizing the format are aware of the image depth and
409 others need not know. The <structfield>palette</structfield> field
410 moved into the &v4l2-pix-format;:<informaltable>
414 <entry>struct <structname>video_picture</structname>
415 <structfield>palette</structfield></entry>
416 <entry>&v4l2-pix-format;
417 <structfield>pixfmt</structfield></entry>
422 <entry><constant>VIDEO_PALETTE_GREY</constant></entry>
424 linkend="V4L2-PIX-FMT-GREY"><constant>V4L2_PIX_FMT_GREY</constant></link></para></entry>
427 <entry><constant>VIDEO_PALETTE_HI240</constant></entry>
429 linkend="pixfmt-reserved"><constant>V4L2_PIX_FMT_HI240</constant></link><footnote>
430 <para>This is a custom format used by the BTTV
431 driver, not one of the V4L2 standard formats.</para>
432 </footnote></para></entry>
435 <entry><constant>VIDEO_PALETTE_RGB565</constant></entry>
437 linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB565</constant></link></para></entry>
440 <entry><constant>VIDEO_PALETTE_RGB555</constant></entry>
442 linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_RGB555</constant></link></para></entry>
445 <entry><constant>VIDEO_PALETTE_RGB24</constant></entry>
447 linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR24</constant></link></para></entry>
450 <entry><constant>VIDEO_PALETTE_RGB32</constant></entry>
452 linkend="pixfmt-rgb"><constant>V4L2_PIX_FMT_BGR32</constant></link><footnote>
453 <para>Presumably all V4L RGB formats are
454 little-endian, although some drivers might interpret them according to machine endianess. V4L2 defines little-endian, big-endian and red/blue
455 swapped variants. For details see <xref linkend="pixfmt-rgb" />.</para>
456 </footnote></para></entry>
459 <entry><constant>VIDEO_PALETTE_YUV422</constant></entry>
461 linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry>
464 <entry><para><constant>VIDEO_PALETTE_YUYV</constant><footnote>
465 <para><constant>VIDEO_PALETTE_YUV422</constant>
466 and <constant>VIDEO_PALETTE_YUYV</constant> are the same formats. Some
467 V4L drivers respond to one, some to the other.</para>
468 </footnote></para></entry>
470 linkend="V4L2-PIX-FMT-YUYV"><constant>V4L2_PIX_FMT_YUYV</constant></link></para></entry>
473 <entry><constant>VIDEO_PALETTE_UYVY</constant></entry>
475 linkend="V4L2-PIX-FMT-UYVY"><constant>V4L2_PIX_FMT_UYVY</constant></link></para></entry>
478 <entry><constant>VIDEO_PALETTE_YUV420</constant></entry>
482 <entry><constant>VIDEO_PALETTE_YUV411</constant></entry>
484 linkend="V4L2-PIX-FMT-Y41P"><constant>V4L2_PIX_FMT_Y41P</constant></link><footnote>
485 <para>Not to be confused with
486 <constant>V4L2_PIX_FMT_YUV411P</constant>, which is a planar
487 format.</para> </footnote></para></entry>
490 <entry><constant>VIDEO_PALETTE_RAW</constant></entry>
491 <entry><para>None<footnote> <para>V4L explains this
492 as: "RAW capture (BT848)"</para> </footnote></para></entry>
495 <entry><constant>VIDEO_PALETTE_YUV422P</constant></entry>
497 linkend="V4L2-PIX-FMT-YUV422P"><constant>V4L2_PIX_FMT_YUV422P</constant></link></para></entry>
500 <entry><constant>VIDEO_PALETTE_YUV411P</constant></entry>
502 linkend="V4L2-PIX-FMT-YUV411P"><constant>V4L2_PIX_FMT_YUV411P</constant></link><footnote>
503 <para>Not to be confused with
504 <constant>V4L2_PIX_FMT_Y41P</constant>, which is a packed
505 format.</para> </footnote></para></entry>
508 <entry><constant>VIDEO_PALETTE_YUV420P</constant></entry>
510 linkend="V4L2-PIX-FMT-YVU420"><constant>V4L2_PIX_FMT_YVU420</constant></link></para></entry>
513 <entry><constant>VIDEO_PALETTE_YUV410P</constant></entry>
515 linkend="V4L2-PIX-FMT-YVU410"><constant>V4L2_PIX_FMT_YVU410</constant></link></para></entry>
519 </informaltable></para>
521 <para>V4L2 image formats are defined in <xref
522 linkend="pixfmt" />. The image format can be selected with the
523 &VIDIOC-S-FMT; ioctl.</para>
529 <para>The <constant>VIDIOCGAUDIO</constant> and
530 <constant>VIDIOCSAUDIO</constant> ioctl and struct
531 <structname>video_audio</structname> are used to enumerate the
532 audio inputs of a V4L device. The equivalent V4L2 ioctls are
533 &VIDIOC-G-AUDIO; and &VIDIOC-S-AUDIO; using &v4l2-audio; as
534 discussed in <xref linkend="audio" />.</para>
536 <para>The <structfield>audio</structfield> "channel number"
537 field counting audio inputs was renamed to
538 <structfield>index</structfield>.</para>
540 <para>On <constant>VIDIOCSAUDIO</constant> the
541 <structfield>mode</structfield> field selects <emphasis>one</emphasis>
542 of the <constant>VIDEO_SOUND_MONO</constant>,
543 <constant>VIDEO_SOUND_STEREO</constant>,
544 <constant>VIDEO_SOUND_LANG1</constant> or
545 <constant>VIDEO_SOUND_LANG2</constant> audio demodulation modes. When
546 the current audio standard is BTSC
547 <constant>VIDEO_SOUND_LANG2</constant> refers to SAP and
548 <constant>VIDEO_SOUND_LANG1</constant> is meaningless. Also
549 undocumented in the V4L specification, there is no way to query the
550 selected mode. On <constant>VIDIOCGAUDIO</constant> the driver returns
551 the <emphasis>actually received</emphasis> audio programmes in this
552 field. In the V4L2 API this information is stored in the &v4l2-tuner;
553 <structfield>rxsubchans</structfield> and
554 <structfield>audmode</structfield> fields, respectively. See <xref
555 linkend="tuner" /> for more information on tuners. Related to audio
556 modes &v4l2-audio; also reports if this is a mono or stereo
557 input, regardless if the source is a tuner.</para>
559 <para>The following fields where replaced by V4L2 controls
560 accessible with the &VIDIOC-QUERYCTRL;, &VIDIOC-G-CTRL; and
561 &VIDIOC-S-CTRL; ioctls:<informaltable>
566 <structname>video_audio</structname></entry>
567 <entry>V4L2 Control ID</entry>
572 <entry><structfield>volume</structfield></entry>
573 <entry><constant>V4L2_CID_AUDIO_VOLUME</constant></entry>
576 <entry><structfield>bass</structfield></entry>
577 <entry><constant>V4L2_CID_AUDIO_BASS</constant></entry>
580 <entry><structfield>treble</structfield></entry>
581 <entry><constant>V4L2_CID_AUDIO_TREBLE</constant></entry>
584 <entry><structfield>balance</structfield></entry>
585 <entry><constant>V4L2_CID_AUDIO_BALANCE</constant></entry>
589 </informaltable></para>
591 <para>To determine which of these controls are supported by a
592 driver V4L provides the <structfield>flags</structfield>
593 <constant>VIDEO_AUDIO_VOLUME</constant>,
594 <constant>VIDEO_AUDIO_BASS</constant>,
595 <constant>VIDEO_AUDIO_TREBLE</constant> and
596 <constant>VIDEO_AUDIO_BALANCE</constant>. In the V4L2 API the
597 &VIDIOC-QUERYCTRL; ioctl reports if the respective control is
598 supported. Accordingly the <constant>VIDEO_AUDIO_MUTABLE</constant>
599 and <constant>VIDEO_AUDIO_MUTE</constant> flags where replaced by the
600 boolean <constant>V4L2_CID_AUDIO_MUTE</constant> control.</para>
602 <para>All V4L2 controls have a <structfield>step</structfield>
603 attribute replacing the struct <structname>video_audio</structname>
604 <structfield>step</structfield> field. The V4L audio controls are
605 assumed to range from 0 to 65535 with no particular reset value. The
606 V4L2 API permits arbitrary limits and defaults which can be queried
607 with the &VIDIOC-QUERYCTRL; ioctl. For general information about
608 controls see <xref linkend="control" />.</para>
612 <title>Frame Buffer Overlay</title>
614 <para>The V4L2 ioctls equivalent to
615 <constant>VIDIOCGFBUF</constant> and <constant>VIDIOCSFBUF</constant>
616 are &VIDIOC-G-FBUF; and &VIDIOC-S-FBUF;. The
617 <structfield>base</structfield> field of struct
618 <structname>video_buffer</structname> remained unchanged, except V4L2
619 defines a flag to indicate non-destructive overlays instead of a
620 <constant>NULL</constant> pointer. All other fields moved into the
621 &v4l2-pix-format; <structfield>fmt</structfield> substructure of
622 &v4l2-framebuffer;. The <structfield>depth</structfield> field was
623 replaced by <structfield>pixelformat</structfield>. See <xref
624 linkend="pixfmt-rgb" /> for a list of RGB formats and their
625 respective color depths.</para>
627 <para>Instead of the special ioctls
628 <constant>VIDIOCGWIN</constant> and <constant>VIDIOCSWIN</constant>
629 V4L2 uses the general-purpose data format negotiation ioctls
630 &VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a
631 &v4l2-format; as argument. Here the <structfield>win</structfield>
632 member of the <structfield>fmt</structfield> union is used, a
633 &v4l2-window;.</para>
635 <para>The <structfield>x</structfield>,
636 <structfield>y</structfield>, <structfield>width</structfield> and
637 <structfield>height</structfield> fields of struct
638 <structname>video_window</structname> moved into &v4l2-rect;
639 substructure <structfield>w</structfield> of struct
640 <structname>v4l2_window</structname>. The
641 <structfield>chromakey</structfield>,
642 <structfield>clips</structfield>, and
643 <structfield>clipcount</structfield> fields remained unchanged. Struct
644 <structname>video_clip</structname> was renamed to &v4l2-clip;, also
645 containing a struct <structname>v4l2_rect</structname>, but the
646 semantics are still the same.</para>
648 <para>The <constant>VIDEO_WINDOW_INTERLACE</constant> flag was
649 dropped. Instead applications must set the
650 <structfield>field</structfield> field to
651 <constant>V4L2_FIELD_ANY</constant> or
652 <constant>V4L2_FIELD_INTERLACED</constant>. The
653 <constant>VIDEO_WINDOW_CHROMAKEY</constant> flag moved into
654 &v4l2-framebuffer;, under the new name
655 <constant>V4L2_FBUF_FLAG_CHROMAKEY</constant>.</para>
657 <para>In V4L, storing a bitmap pointer in
658 <structfield>clips</structfield> and setting
659 <structfield>clipcount</structfield> to
660 <constant>VIDEO_CLIP_BITMAP</constant> (-1) requests bitmap
661 clipping, using a fixed size bitmap of 1024 × 625 bits. Struct
662 <structname>v4l2_window</structname> has a separate
663 <structfield>bitmap</structfield> pointer field for this purpose and
664 the bitmap size is determined by <structfield>w.width</structfield> and
665 <structfield>w.height</structfield>.</para>
667 <para>The <constant>VIDIOCCAPTURE</constant> ioctl to enable or
668 disable overlay was renamed to &VIDIOC-OVERLAY;.</para>
672 <title>Cropping</title>
674 <para>To capture only a subsection of the full picture V4L
675 defines the <constant>VIDIOCGCAPTURE</constant> and
676 <constant>VIDIOCSCAPTURE</constant> ioctls using struct
677 <structname>video_capture</structname>. The equivalent V4L2 ioctls are
678 &VIDIOC-G-CROP; and &VIDIOC-S-CROP; using &v4l2-crop;, and the related
679 &VIDIOC-CROPCAP; ioctl. This is a rather complex matter, see
680 <xref linkend="crop" /> for details.</para>
682 <para>The <structfield>x</structfield>,
683 <structfield>y</structfield>, <structfield>width</structfield> and
684 <structfield>height</structfield> fields moved into &v4l2-rect;
685 substructure <structfield>c</structfield> of struct
686 <structname>v4l2_crop</structname>. The
687 <structfield>decimation</structfield> field was dropped. In the V4L2
688 API the scaling factor is implied by the size of the cropping
689 rectangle and the size of the captured or overlaid image.</para>
691 <para>The <constant>VIDEO_CAPTURE_ODD</constant>
692 and <constant>VIDEO_CAPTURE_EVEN</constant> flags to capture only the
693 odd or even field, respectively, were replaced by
694 <constant>V4L2_FIELD_TOP</constant> and
695 <constant>V4L2_FIELD_BOTTOM</constant> in the field named
696 <structfield>field</structfield> of &v4l2-pix-format; and
697 &v4l2-window;. These structures are used to select a capture or
698 overlay format with the &VIDIOC-S-FMT; ioctl.</para>
702 <title>Reading Images, Memory Mapping</title>
705 <title>Capturing using the read method</title>
707 <para>There is no essential difference between reading images
708 from a V4L or V4L2 device using the &func-read; function, however V4L2
709 drivers are not required to support this I/O method. Applications can
710 determine if the function is available with the &VIDIOC-QUERYCAP;
711 ioctl. All V4L2 devices exchanging data with applications must support
712 the &func-select; and &func-poll; functions.</para>
714 <para>To select an image format and size, V4L provides the
715 <constant>VIDIOCSPICT</constant> and <constant>VIDIOCSWIN</constant>
716 ioctls. V4L2 uses the general-purpose data format negotiation ioctls
717 &VIDIOC-G-FMT; and &VIDIOC-S-FMT;. They take a pointer to a
718 &v4l2-format; as argument, here the &v4l2-pix-format; named
719 <structfield>pix</structfield> of its <structfield>fmt</structfield>
720 union is used.</para>
722 <para>For more information about the V4L2 read interface see
723 <xref linkend="rw" />.</para>
726 <title>Capturing using memory mapping</title>
728 <para>Applications can read from V4L devices by mapping
729 buffers in device memory, or more often just buffers allocated in
730 DMA-able system memory, into their address space. This avoids the data
731 copying overhead of the read method. V4L2 supports memory mapping as
732 well, with a few differences.</para>
745 <entry>The image format must be selected before
746 buffers are allocated, with the &VIDIOC-S-FMT; ioctl. When no format
747 is selected the driver may use the last, possibly by another
748 application requested format.</entry>
751 <entry><para>Applications cannot change the number of
752 buffers. The it is built into the driver, unless it has a module
753 option to change the number when the driver module is
754 loaded.</para></entry>
755 <entry><para>The &VIDIOC-REQBUFS; ioctl allocates the
756 desired number of buffers, this is a required step in the initialization
757 sequence.</para></entry>
760 <entry><para>Drivers map all buffers as one contiguous
761 range of memory. The <constant>VIDIOCGMBUF</constant> ioctl is
762 available to query the number of buffers, the offset of each buffer
763 from the start of the virtual file, and the overall amount of memory
764 used, which can be used as arguments for the &func-mmap;
765 function.</para></entry>
766 <entry><para>Buffers are individually mapped. The
767 offset and size of each buffer can be determined with the
768 &VIDIOC-QUERYBUF; ioctl.</para></entry>
771 <entry><para>The <constant>VIDIOCMCAPTURE</constant>
772 ioctl prepares a buffer for capturing. It also determines the image
773 format for this buffer. The ioctl returns immediately, eventually with
774 an &EAGAIN; if no video signal had been detected. When the driver
775 supports more than one buffer applications can call the ioctl multiple
776 times and thus have multiple outstanding capture
777 requests.</para><para>The <constant>VIDIOCSYNC</constant> ioctl
778 suspends execution until a particular buffer has been
779 filled.</para></entry>
780 <entry><para>Drivers maintain an incoming and outgoing
781 queue. &VIDIOC-QBUF; enqueues any empty buffer into the incoming
782 queue. Filled buffers are dequeued from the outgoing queue with the
783 &VIDIOC-DQBUF; ioctl. To wait until filled buffers become available this
784 function, &func-select; or &func-poll; can be used. The
785 &VIDIOC-STREAMON; ioctl must be called once after enqueuing one or
786 more buffers to start capturing. Its counterpart
787 &VIDIOC-STREAMOFF; stops capturing and dequeues all buffers from both
788 queues. Applications can query the signal status, if known, with the
789 &VIDIOC-ENUMINPUT; ioctl.</para></entry>
795 <para>For a more in-depth discussion of memory mapping and
796 examples, see <xref linkend="mmap" />.</para>
801 <title>Reading Raw VBI Data</title>
803 <para>Originally the V4L API did not specify a raw VBI capture
804 interface, only the device file <filename>/dev/vbi</filename> was
805 reserved for this purpose. The only driver supporting this interface
806 was the BTTV driver, de-facto defining the V4L VBI interface. Reading
807 from the device yields a raw VBI image with the following
808 parameters:<informaltable>
812 <entry>&v4l2-vbi-format;</entry>
813 <entry>V4L, BTTV driver</entry>
818 <entry>sampling_rate</entry>
819 <entry>28636363 Hz NTSC (or any other 525-line
820 standard); 35468950 Hz PAL and SECAM (625-line standards)</entry>
823 <entry>offset</entry>
827 <entry>samples_per_line</entry>
831 <entry>sample_format</entry>
832 <entry>V4L2_PIX_FMT_GREY. The last four bytes (a
833 machine endianess integer) contain a frame counter.</entry>
836 <entry>start[]</entry>
837 <entry>10, 273 NTSC; 22, 335 PAL and SECAM</entry>
840 <entry>count[]</entry>
841 <entry><para>16, 16<footnote><para>Old driver
842 versions used different values, eventually the custom
843 <constant>BTTV_VBISIZE</constant> ioctl was added to query the
844 correct values.</para></footnote></para></entry>
852 </informaltable></para>
854 <para>Undocumented in the V4L specification, in Linux 2.3 the
855 <constant>VIDIOCGVBIFMT</constant> and
856 <constant>VIDIOCSVBIFMT</constant> ioctls using struct
857 <structname>vbi_format</structname> were added to determine the VBI
858 image parameters. These ioctls are only partially compatible with the
859 V4L2 VBI interface specified in <xref linkend="raw-vbi" />.</para>
861 <para>An <structfield>offset</structfield> field does not
862 exist, <structfield>sample_format</structfield> is supposed to be
863 <constant>VIDEO_PALETTE_RAW</constant>, equivalent to
864 <constant>V4L2_PIX_FMT_GREY</constant>. The remaining fields are
865 probably equivalent to &v4l2-vbi-format;.</para>
867 <para>Apparently only the Zoran (ZR 36120) driver implements
868 these ioctls. The semantics differ from those specified for V4L2 in two
869 ways. The parameters are reset on &func-open; and
870 <constant>VIDIOCSVBIFMT</constant> always returns an &EINVAL; if the
871 parameters are invalid.</para>
875 <title>Miscellaneous</title>
877 <para>V4L2 has no equivalent of the
878 <constant>VIDIOCGUNIT</constant> ioctl. Applications can find the VBI
879 device associated with a video capture device (or vice versa) by
880 reopening the device and requesting VBI data. For details see
881 <xref linkend="open" />.</para>
883 <para>No replacement exists for <constant>VIDIOCKEY</constant>,
884 and the V4L functions for microcode programming. A new interface for
885 MPEG compression and playback devices is documented in <xref
886 linkend="extended-controls" />.</para>
891 <section id="hist-v4l2">
892 <title>Changes of the V4L2 API</title>
894 <para>Soon after the V4L API was added to the kernel it was
895 criticised as too inflexible. In August 1998 Bill Dirks proposed a
896 number of improvements and began to work on documentation, example
897 drivers and applications. With the help of other volunteers this
898 eventually became the V4L2 API, not just an extension but a
899 replacement for the V4L API. However it took another four years and
900 two stable kernel releases until the new API was finally accepted for
901 inclusion into the kernel in its present form.</para>
904 <title>Early Versions</title>
905 <para>1998-08-20: First version.</para>
907 <para>1998-08-27: The &func-select; function was introduced.</para>
909 <para>1998-09-10: New video standard interface.</para>
911 <para>1998-09-18: The <constant>VIDIOC_NONCAP</constant> ioctl
912 was replaced by the otherwise meaningless <constant>O_TRUNC</constant>
913 &func-open; flag, and the aliases <constant>O_NONCAP</constant> and
914 <constant>O_NOIO</constant> were defined. Applications can set this
915 flag if they intend to access controls only, as opposed to capture
916 applications which need exclusive access. The
917 <constant>VIDEO_STD_XXX</constant> identifiers are now ordinals
918 instead of flags, and the <function>video_std_construct()</function>
919 helper function takes id and transmission arguments.</para>
921 <para>1998-09-28: Revamped video standard. Made video controls
922 individually enumerable.</para>
924 <para>1998-10-02: The <structfield>id</structfield> field was
925 removed from struct <structname>video_standard</structname> and the
926 color subcarrier fields were renamed. The &VIDIOC-QUERYSTD; ioctl was
927 renamed to &VIDIOC-ENUMSTD;, &VIDIOC-G-INPUT; to &VIDIOC-ENUMINPUT;. A
928 first draft of the Codec API was released.</para>
930 <para>1998-11-08: Many minor changes. Most symbols have been
931 renamed. Some material changes to &v4l2-capability;.</para>
933 <para>1998-11-12: The read/write directon of some ioctls was misdefined.</para>
935 <para>1998-11-14: <constant>V4L2_PIX_FMT_RGB24</constant>
936 changed to <constant>V4L2_PIX_FMT_BGR24</constant>, and
937 <constant>V4L2_PIX_FMT_RGB32</constant> changed to
938 <constant>V4L2_PIX_FMT_BGR32</constant>. Audio controls are now
939 accessible with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls under
940 names starting with <constant>V4L2_CID_AUDIO</constant>. The
941 <constant>V4L2_MAJOR</constant> define was removed from
942 <filename>videodev.h</filename> since it was only used once in the
943 <filename>videodev</filename> kernel module. The
944 <constant>YUV422</constant> and <constant>YUV411</constant> planar
945 image formats were added.</para>
947 <para>1998-11-28: A few ioctl symbols changed. Interfaces for codecs and
948 video output devices were added.</para>
950 <para>1999-01-14: A raw VBI capture interface was added.</para>
952 <para>1999-01-19: The <constant>VIDIOC_NEXTBUF</constant> ioctl
957 <title>V4L2 Version 0.16 1999-01-31</title>
958 <para>1999-01-27: There is now one QBUF ioctl, VIDIOC_QWBUF and VIDIOC_QRBUF
959 are gone. VIDIOC_QBUF takes a v4l2_buffer as a parameter. Added
960 digital zoom (cropping) controls.</para>
963 <!-- Where's 0.17? mhs couldn't find that videodev.h, perhaps Bill
964 forgot to bump the version number or never released it. -->
967 <title>V4L2 Version 0.18 1999-03-16</title>
968 <para>Added a v4l to V4L2 ioctl compatibility layer to
969 videodev.c. Driver writers, this changes how you implement your ioctl
970 handler. See the Driver Writer's Guide. Added some more control id
975 <title>V4L2 Version 0.19 1999-06-05</title>
976 <para>1999-03-18: Fill in the category and catname fields of
977 v4l2_queryctrl objects before passing them to the driver. Required a
978 minor change to the VIDIOC_QUERYCTRL handlers in the sample
980 <para>1999-03-31: Better compatibility for v4l memory capture
981 ioctls. Requires changes to drivers to fully support new compatibility
982 features, see Driver Writer's Guide and v4l2cap.c. Added new control
983 IDs: V4L2_CID_HFLIP, _VFLIP. Changed V4L2_PIX_FMT_YUV422P to _YUV422P,
984 and _YUV411P to _YUV411P.</para>
985 <para>1999-04-04: Added a few more control IDs.</para>
986 <para>1999-04-07: Added the button control type.</para>
987 <para>1999-05-02: Fixed a typo in videodev.h, and added the
988 V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag.</para>
989 <para>1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing
990 a malfunction of this ioctl.</para>
991 <para>1999-06-05: Changed the value of
992 V4L2_CID_WHITENESS.</para>
996 <title>V4L2 Version 0.20 (1999-09-10)</title>
998 <para>Version 0.20 introduced a number of changes which were
999 <emphasis>not backward compatible</emphasis> with 0.19 and earlier
1000 versions. Purpose of these changes was to simplify the API, while
1001 making it more extensible and following common Linux driver API
1006 <para>Some typos in <constant>V4L2_FMT_FLAG</constant>
1007 symbols were fixed. &v4l2-clip; was changed for compatibility with
1008 v4l. (1999-08-30)</para>
1012 <para><constant>V4L2_TUNER_SUB_LANG1</constant> was added.
1017 <para>All ioctl() commands that used an integer argument now
1018 take a pointer to an integer. Where it makes sense, ioctls will return
1019 the actual new value in the integer pointed to by the argument, a
1020 common convention in the V4L2 API. The affected ioctls are:
1021 VIDIOC_PREVIEW, VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ,
1022 VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example
1024 err = ioctl (fd, VIDIOC_XXX, V4L2_XXX);
1025 </programlisting> becomes <programlisting>
1026 int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a);
1032 <para>All the different get- and set-format commands were
1033 swept into one &VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctl taking a union
1034 and a type field selecting the union member as parameter. Purpose is to
1035 simplify the API by eliminating several ioctls and to allow new and
1036 driver private data streams without adding new ioctls.</para>
1038 <para>This change obsoletes the following ioctls:
1039 <constant>VIDIOC_S_INFMT</constant>,
1040 <constant>VIDIOC_G_INFMT</constant>,
1041 <constant>VIDIOC_S_OUTFMT</constant>,
1042 <constant>VIDIOC_G_OUTFMT</constant>,
1043 <constant>VIDIOC_S_VBIFMT</constant> and
1044 <constant>VIDIOC_G_VBIFMT</constant>. The image format structure
1045 <structname>v4l2_format</structname> was renamed to &v4l2-pix-format;,
1046 while &v4l2-format; is now the envelopping structure for all format
1047 negotiations.</para>
1051 <para>Similar to the changes above, the
1052 <constant>VIDIOC_G_PARM</constant> and
1053 <constant>VIDIOC_S_PARM</constant> ioctls were merged with
1054 <constant>VIDIOC_G_OUTPARM</constant> and
1055 <constant>VIDIOC_S_OUTPARM</constant>. A
1056 <structfield>type</structfield> field in the new &v4l2-streamparm;
1057 selects the respective union member.</para>
1059 <para>This change obsoletes the
1060 <constant>VIDIOC_G_OUTPARM</constant> and
1061 <constant>VIDIOC_S_OUTPARM</constant> ioctls.</para>
1065 <para>Control enumeration was simplified, and two new
1066 control flags were introduced and one dropped. The
1067 <structfield>catname</structfield> field was replaced by a
1068 <structfield>group</structfield> field.</para>
1070 <para>Drivers can now flag unsupported and temporarily
1071 unavailable controls with <constant>V4L2_CTRL_FLAG_DISABLED</constant>
1072 and <constant>V4L2_CTRL_FLAG_GRABBED</constant> respectively. The
1073 <structfield>group</structfield> name indicates a possibly narrower
1074 classification than the <structfield>category</structfield>. In other
1075 words, there may be multiple groups within a category. Controls within
1076 a group would typically be drawn within a group box. Controls in
1077 different categories might have a greater separation, or may even
1078 appear in separate windows.</para>
1082 <para>The &v4l2-buffer; <structfield>timestamp</structfield>
1083 was changed to a 64 bit integer, containing the sampling or output
1084 time of the frame in nanoseconds. Additionally timestamps will be in
1085 absolute system time, not starting from zero at the beginning of a
1086 stream. The data type name for timestamps is stamp_t, defined as a
1087 signed 64-bit integer. Output devices should not send a buffer out
1088 until the time in the timestamp field has arrived. I would like to
1089 follow SGI's lead, and adopt a multimedia timestamping system like
1090 their UST (Unadjusted System Time). See
1091 http://web.archive.org/web/*/http://reality.sgi.com
1092 /cpirazzi_engr/lg/time/intro.html.
1093 UST uses timestamps that are 64-bit signed integers
1094 (not struct timeval's) and given in nanosecond units. The UST clock
1095 starts at zero when the system is booted and runs continuously and
1096 uniformly. It takes a little over 292 years for UST to overflow. There
1097 is no way to set the UST clock. The regular Linux time-of-day clock
1098 can be changed periodically, which would cause errors if it were being
1099 used for timestamping a multimedia stream. A real UST style clock will
1100 require some support in the kernel that is not there yet. But in
1101 anticipation, I will change the timestamp field to a 64-bit integer,
1102 and I will change the v4l2_masterclock_gettime() function (used only
1103 by drivers) to return a 64-bit integer.</para>
1107 <para>A <structfield>sequence</structfield> field was added
1108 to &v4l2-buffer;. The <structfield>sequence</structfield> field counts
1109 captured frames, it is ignored by output devices. When a capture
1110 driver drops a frame, the sequence number of that frame is
1117 <title>V4L2 Version 0.20 incremental changes</title>
1118 <!-- Version number didn't change anymore, reason unknown. -->
1120 <para>1999-12-23: In &v4l2-vbi-format; the
1121 <structfield>reserved1</structfield> field became
1122 <structfield>offset</structfield>. Previously drivers were required to
1123 clear the <structfield>reserved1</structfield> field.</para>
1125 <para>2000-01-13: The
1126 <constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant> flag was added.</para>
1128 <para>2000-07-31: The <filename>linux/poll.h</filename> header
1129 is now included by <filename>videodev.h</filename> for compatibility
1130 with the original <filename>videodev.h</filename> file.</para>
1132 <para>2000-11-20: <constant>V4L2_TYPE_VBI_OUTPUT</constant> and
1133 <constant>V4L2_PIX_FMT_Y41P</constant> were added.</para>
1135 <para>2000-11-25: <constant>V4L2_TYPE_VBI_INPUT</constant> was
1138 <para>2000-12-04: A couple typos in symbol names were fixed.</para>
1140 <para>2001-01-18: To avoid namespace conflicts the
1141 <constant>fourcc</constant> macro defined in the
1142 <filename>videodev.h</filename> header file was renamed to
1143 <constant>v4l2_fourcc</constant>.</para>
1145 <para>2001-01-25: A possible driver-level compatibility problem
1146 between the <filename>videodev.h</filename> file in Linux 2.4.0 and
1147 the <filename>videodev.h</filename> file included in the
1148 <filename>videodevX</filename> patch was fixed. Users of an earlier
1149 version of <filename>videodevX</filename> on Linux 2.4.0 should
1150 recompile their V4L and V4L2 drivers.</para>
1152 <para>2001-01-26: A possible kernel-level incompatibility
1153 between the <filename>videodev.h</filename> file in the
1154 <filename>videodevX</filename> patch and the
1155 <filename>videodev.h</filename> file in Linux 2.2.x with devfs patches
1156 applied was fixed.</para>
1158 <para>2001-03-02: Certain V4L ioctls which pass data in both
1159 direction although they are defined with read-only parameter, did not
1160 work correctly through the backward compatibility layer.
1163 <para>2001-04-13: Big endian 16-bit RGB formats were added.</para>
1165 <para>2001-09-17: New YUV formats and the &VIDIOC-G-FREQUENCY; and
1166 &VIDIOC-S-FREQUENCY; ioctls were added. (The old
1167 <constant>VIDIOC_G_FREQ</constant> and
1168 <constant>VIDIOC_S_FREQ</constant> ioctls did not take multiple tuners
1169 into account.)</para>
1171 <para>2000-09-18: <constant>V4L2_BUF_TYPE_VBI</constant> was
1172 added. This may <emphasis>break compatibility</emphasis> as the
1173 &VIDIOC-G-FMT; and &VIDIOC-S-FMT; ioctls may fail now if the struct
1174 <structname>v4l2_fmt</structname> <structfield>type</structfield>
1175 field does not contain <constant>V4L2_BUF_TYPE_VBI</constant>. In the
1176 documentation of the &v4l2-vbi-format;
1177 <structfield>offset</structfield> field the ambiguous phrase "rising
1178 edge" was changed to "leading edge".</para>
1182 <title>V4L2 Version 0.20 2000-11-23</title>
1184 <para>A number of changes were made to the raw VBI
1189 <para>Figures clarifying the line numbering scheme were
1190 added to the V4L2 API specification. The
1191 <structfield>start</structfield>[0] and
1192 <structfield>start</structfield>[1] fields no longer count line
1193 numbers beginning at zero. Rationale: a) The previous definition was
1194 unclear. b) The <structfield>start</structfield>[] values are ordinal
1195 numbers. c) There is no point in inventing a new line numbering
1196 scheme. We now use line number as defined by ITU-R, period.
1197 Compatibility: Add one to the start values. Applications depending on
1198 the previous semantics may not function correctly.</para>
1202 <para>The restriction "count[0] > 0 and count[1] > 0"
1203 has been relaxed to "(count[0] + count[1]) > 0". Rationale:
1204 Drivers may allocate resources at scan line granularity and some data
1205 services are transmitted only on the first field. The comment that
1206 both <structfield>count</structfield> values will usually be equal is
1207 misleading and pointless and has been removed. This change
1208 <emphasis>breaks compatibility</emphasis> with earlier versions:
1209 Drivers may return EINVAL, applications may not function
1214 <para>Drivers are again permitted to return negative
1215 (unknown) start values as proposed earlier. Why this feature was
1216 dropped is unclear. This change may <emphasis>break
1217 compatibility</emphasis> with applications depending on the start
1218 values being positive. The use of <constant>EBUSY</constant> and
1219 <constant>EINVAL</constant> error codes with the &VIDIOC-S-FMT; ioctl
1220 was clarified. The &EBUSY; was finally documented, and the
1221 <structfield>reserved2</structfield> field which was previously
1222 mentioned only in the <filename>videodev.h</filename> header
1227 <para>New buffer types
1228 <constant>V4L2_TYPE_VBI_INPUT</constant> and
1229 <constant>V4L2_TYPE_VBI_OUTPUT</constant> were added. The former is an
1230 alias for the old <constant>V4L2_TYPE_VBI</constant>, the latter was
1231 missing in the <filename>videodev.h</filename> file.</para>
1237 <title>V4L2 Version 0.20 2002-07-25</title>
1238 <para>Added sliced VBI interface proposal.</para>
1242 <title>V4L2 in Linux 2.5.46, 2002-10</title>
1244 <para>Around October-November 2002, prior to an announced
1245 feature freeze of Linux 2.5, the API was revised, drawing from
1246 experience with V4L2 0.20. This unnamed version was finally merged
1247 into Linux 2.5.46.</para>
1251 <para>As specified in <xref linkend="related" />, drivers
1252 must make related device functions available under all minor device
1257 <para>The &func-open; function requires access mode
1258 <constant>O_RDWR</constant> regardless of the device type. All V4L2
1259 drivers exchanging data with applications must support the
1260 <constant>O_NONBLOCK</constant> flag. The <constant>O_NOIO</constant>
1261 flag, a V4L2 symbol which aliased the meaningless
1262 <constant>O_TRUNC</constant> to indicate accesses without data
1263 exchange (panel applications) was dropped. Drivers must stay in "panel
1264 mode" until the application attempts to initiate a data exchange, see
1265 <xref linkend="open" />.</para>
1269 <para>The &v4l2-capability; changed dramatically. Note that
1270 also the size of the structure changed, which is encoded in the ioctl
1271 request code, thus older V4L2 devices will respond with an &EINVAL; to
1272 the new &VIDIOC-QUERYCAP; ioctl.</para>
1274 <para>There are new fields to identify the driver, a new RDS
1275 device function <constant>V4L2_CAP_RDS_CAPTURE</constant>, the
1276 <constant>V4L2_CAP_AUDIO</constant> flag indicates if the device has
1277 any audio connectors, another I/O capability
1278 <constant>V4L2_CAP_ASYNCIO</constant> can be flagged. In response to
1279 these changes the <structfield>type</structfield> field became a bit
1280 set and was merged into the <structfield>flags</structfield> field.
1281 <constant>V4L2_FLAG_TUNER</constant> was renamed to
1282 <constant>V4L2_CAP_TUNER</constant>,
1283 <constant>V4L2_CAP_VIDEO_OVERLAY</constant> replaced
1284 <constant>V4L2_FLAG_PREVIEW</constant> and
1285 <constant>V4L2_CAP_VBI_CAPTURE</constant> and
1286 <constant>V4L2_CAP_VBI_OUTPUT</constant> replaced
1287 <constant>V4L2_FLAG_DATA_SERVICE</constant>.
1288 <constant>V4L2_FLAG_READ</constant> and
1289 <constant>V4L2_FLAG_WRITE</constant> were merged into
1290 <constant>V4L2_CAP_READWRITE</constant>.</para>
1292 <para>The redundant fields
1293 <structfield>inputs</structfield>, <structfield>outputs</structfield>
1294 and <structfield>audios</structfield> were removed. These properties
1295 can be determined as described in <xref linkend="video" /> and <xref
1296 linkend="audio" />.</para>
1298 <para>The somewhat volatile and therefore barely useful
1299 fields <structfield>maxwidth</structfield>,
1300 <structfield>maxheight</structfield>,
1301 <structfield>minwidth</structfield>,
1302 <structfield>minheight</structfield>,
1303 <structfield>maxframerate</structfield> were removed. This information
1304 is available as described in <xref linkend="format" /> and
1305 <xref linkend="standard" />.</para>
1307 <para><constant>V4L2_FLAG_SELECT</constant> was removed. We
1308 believe the select() function is important enough to require support
1309 of it in all V4L2 drivers exchanging data with applications. The
1310 redundant <constant>V4L2_FLAG_MONOCHROME</constant> flag was removed,
1311 this information is available as described in <xref
1312 linkend="format" />.</para>
1316 <para>In &v4l2-input; the
1317 <structfield>assoc_audio</structfield> field and the
1318 <structfield>capability</structfield> field and its only flag
1319 <constant>V4L2_INPUT_CAP_AUDIO</constant> was replaced by the new
1320 <structfield>audioset</structfield> field. Instead of linking one
1321 video input to one audio input this field reports all audio inputs
1322 this video input combines with.</para>
1324 <para>New fields are <structfield>tuner</structfield>
1325 (reversing the former link from tuners to video inputs),
1326 <structfield>std</structfield> and
1327 <structfield>status</structfield>.</para>
1329 <para>Accordingly &v4l2-output; lost its
1330 <structfield>capability</structfield> and
1331 <structfield>assoc_audio</structfield> fields.
1332 <structfield>audioset</structfield>,
1333 <structfield>modulator</structfield> and
1334 <structfield>std</structfield> where added instead.</para>
1338 <para>The &v4l2-audio; field
1339 <structfield>audio</structfield> was renamed to
1340 <structfield>index</structfield>, for consistency with other
1341 structures. A new capability flag
1342 <constant>V4L2_AUDCAP_STEREO</constant> was added to indicated if the
1343 audio input in question supports stereo sound.
1344 <constant>V4L2_AUDCAP_EFFECTS</constant> and the corresponding
1345 <constant>V4L2_AUDMODE</constant> flags where removed. This can be
1346 easily implemented using controls. (However the same applies to AVL
1347 which is still there.)</para>
1349 <para>Again for consistency the &v4l2-audioout; field
1350 <structfield>audio</structfield> was renamed to
1351 <structfield>index</structfield>.</para>
1355 <para>The &v4l2-tuner;
1356 <structfield>input</structfield> field was replaced by an
1357 <structfield>index</structfield> field, permitting devices with
1358 multiple tuners. The link between video inputs and tuners is now
1359 reversed, inputs point to their tuner. The
1360 <structfield>std</structfield> substructure became a
1361 simple set (more about this below) and moved into &v4l2-input;. A
1362 <structfield>type</structfield> field was added.</para>
1364 <para>Accordingly in &v4l2-modulator; the
1365 <structfield>output</structfield> was replaced by an
1366 <structfield>index</structfield> field.</para>
1368 <para>In &v4l2-frequency; the
1369 <structfield>port</structfield> field was replaced by a
1370 <structfield>tuner</structfield> field containing the respective tuner
1371 or modulator index number. A tuner <structfield>type</structfield>
1372 field was added and the <structfield>reserved</structfield> field
1373 became larger for future extensions (satellite tuners in
1378 <para>The idea of completely transparent video standards was
1379 dropped. Experience showed that applications must be able to work with
1380 video standards beyond presenting the user a menu. Instead of
1381 enumerating supported standards with an ioctl applications can now
1382 refer to standards by &v4l2-std-id; and symbols defined in the
1383 <filename>videodev2.h</filename> header file. For details see <xref
1384 linkend="standard" />. The &VIDIOC-G-STD; and
1385 &VIDIOC-S-STD; now take a pointer to this type as argument.
1386 &VIDIOC-QUERYSTD; was added to autodetect the received standard, if
1387 the hardware has this capability. In &v4l2-standard; an
1388 <structfield>index</structfield> field was added for &VIDIOC-ENUMSTD;.
1389 A &v4l2-std-id; field named <structfield>id</structfield> was added as
1390 machine readable identifier, also replacing the
1391 <structfield>transmission</structfield> field. The misleading
1392 <structfield>framerate</structfield> field was renamed
1393 to <structfield>frameperiod</structfield>. The now obsolete
1394 <structfield>colorstandard</structfield> information, originally
1395 needed to distguish between variations of standards, were
1398 <para>Struct <structname>v4l2_enumstd</structname> ceased to
1399 be. &VIDIOC-ENUMSTD; now takes a pointer to a &v4l2-standard;
1400 directly. The information which standards are supported by a
1401 particular video input or output moved into &v4l2-input; and
1402 &v4l2-output; fields named <structfield>std</structfield>,
1403 respectively.</para>
1407 <para>The &v4l2-queryctrl; fields
1408 <structfield>category</structfield> and
1409 <structfield>group</structfield> did not catch on and/or were not
1410 implemented as expected and therefore removed.</para>
1414 <para>The &VIDIOC-TRY-FMT; ioctl was added to negotiate data
1415 formats as with &VIDIOC-S-FMT;, but without the overhead of
1416 programming the hardware and regardless of I/O in progress.</para>
1418 <para>In &v4l2-format; the <structfield>fmt</structfield>
1419 union was extended to contain &v4l2-window;. All image format
1420 negotiations are now possible with <constant>VIDIOC_G_FMT</constant>,
1421 <constant>VIDIOC_S_FMT</constant> and
1422 <constant>VIDIOC_TRY_FMT</constant>; ioctl. The
1423 <constant>VIDIOC_G_WIN</constant> and
1424 <constant>VIDIOC_S_WIN</constant> ioctls to prepare for a video
1425 overlay were removed. The <structfield>type</structfield> field
1426 changed to type &v4l2-buf-type; and the buffer type names changed as
1427 follows.<informaltable>
1431 <entry>Old defines</entry>
1432 <entry>&v4l2-buf-type;</entry>
1435 <tbody valign="top">
1437 <entry><constant>V4L2_BUF_TYPE_CAPTURE</constant></entry>
1438 <entry><constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant></entry>
1441 <entry><constant>V4L2_BUF_TYPE_CODECIN</constant></entry>
1442 <entry>Omitted for now</entry>
1445 <entry><constant>V4L2_BUF_TYPE_CODECOUT</constant></entry>
1446 <entry>Omitted for now</entry>
1449 <entry><constant>V4L2_BUF_TYPE_EFFECTSIN</constant></entry>
1450 <entry>Omitted for now</entry>
1453 <entry><constant>V4L2_BUF_TYPE_EFFECTSIN2</constant></entry>
1454 <entry>Omitted for now</entry>
1457 <entry><constant>V4L2_BUF_TYPE_EFFECTSOUT</constant></entry>
1458 <entry>Omitted for now</entry>
1461 <entry><constant>V4L2_BUF_TYPE_VIDEOOUT</constant></entry>
1462 <entry><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT</constant></entry>
1465 <entry><constant>-</constant></entry>
1466 <entry><constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant></entry>
1469 <entry><constant>-</constant></entry>
1470 <entry><constant>V4L2_BUF_TYPE_VBI_CAPTURE</constant></entry>
1473 <entry><constant>-</constant></entry>
1474 <entry><constant>V4L2_BUF_TYPE_VBI_OUTPUT</constant></entry>
1477 <entry><constant>-</constant></entry>
1478 <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant></entry>
1481 <entry><constant>-</constant></entry>
1482 <entry><constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant></entry>
1485 <entry><constant>V4L2_BUF_TYPE_PRIVATE_BASE</constant></entry>
1486 <entry><constant>V4L2_BUF_TYPE_PRIVATE</constant></entry>
1490 </informaltable></para>
1494 <para>In &v4l2-fmtdesc; a &v4l2-buf-type; field named
1495 <structfield>type</structfield> was added as in &v4l2-format;. The
1496 <constant>VIDIOC_ENUM_FBUFFMT</constant> ioctl is no longer needed and
1497 was removed. These calls can be replaced by &VIDIOC-ENUM-FMT; with
1498 type <constant>V4L2_BUF_TYPE_VIDEO_OVERLAY</constant>.</para>
1502 <para>In &v4l2-pix-format; the
1503 <structfield>depth</structfield> field was removed, assuming
1504 applications which recognize the format by its four-character-code
1505 already know the color depth, and others do not care about it. The
1506 same rationale lead to the removal of the
1507 <constant>V4L2_FMT_FLAG_COMPRESSED</constant> flag. The
1508 <constant>V4L2_FMT_FLAG_SWCONVECOMPRESSED</constant> flag was removed
1509 because drivers are not supposed to convert images in kernel space. A
1510 user library of conversion functions should be provided instead. The
1511 <constant>V4L2_FMT_FLAG_BYTESPERLINE</constant> flag was redundant.
1512 Applications can set the <structfield>bytesperline</structfield> field
1513 to zero to get a reasonable default. Since the remaining flags were
1514 replaced as well, the <structfield>flags</structfield> field itself
1516 <para>The interlace flags were replaced by a &v4l2-field;
1517 value in a newly added <structfield>field</structfield>
1518 field.<informaltable>
1522 <entry>Old flag</entry>
1523 <entry>&v4l2-field;</entry>
1526 <tbody valign="top">
1528 <entry><constant>V4L2_FMT_FLAG_NOT_INTERLACED</constant></entry>
1532 <entry><constant>V4L2_FMT_FLAG_INTERLACED</constant>
1533 = <constant>V4L2_FMT_FLAG_COMBINED</constant></entry>
1534 <entry><constant>V4L2_FIELD_INTERLACED</constant></entry>
1537 <entry><constant>V4L2_FMT_FLAG_TOPFIELD</constant>
1538 = <constant>V4L2_FMT_FLAG_ODDFIELD</constant></entry>
1539 <entry><constant>V4L2_FIELD_TOP</constant></entry>
1542 <entry><constant>V4L2_FMT_FLAG_BOTFIELD</constant>
1543 = <constant>V4L2_FMT_FLAG_EVENFIELD</constant></entry>
1544 <entry><constant>V4L2_FIELD_BOTTOM</constant></entry>
1547 <entry><constant>-</constant></entry>
1548 <entry><constant>V4L2_FIELD_SEQ_TB</constant></entry>
1551 <entry><constant>-</constant></entry>
1552 <entry><constant>V4L2_FIELD_SEQ_BT</constant></entry>
1555 <entry><constant>-</constant></entry>
1556 <entry><constant>V4L2_FIELD_ALTERNATE</constant></entry>
1560 </informaltable></para>
1562 <para>The color space flags were replaced by a
1563 &v4l2-colorspace; value in a newly added
1564 <structfield>colorspace</structfield> field, where one of
1565 <constant>V4L2_COLORSPACE_SMPTE170M</constant>,
1566 <constant>V4L2_COLORSPACE_BT878</constant>,
1567 <constant>V4L2_COLORSPACE_470_SYSTEM_M</constant> or
1568 <constant>V4L2_COLORSPACE_470_SYSTEM_BG</constant> replaces
1569 <constant>V4L2_FMT_CS_601YUV</constant>.</para>
1573 <para>In &v4l2-requestbuffers; the
1574 <structfield>type</structfield> field was properly defined as
1575 &v4l2-buf-type;. Buffer types changed as mentioned above. A new
1576 <structfield>memory</structfield> field of type &v4l2-memory; was
1577 added to distinguish between I/O methods using buffers allocated
1578 by the driver or the application. See <xref linkend="io" /> for
1583 <para>In &v4l2-buffer; the <structfield>type</structfield>
1584 field was properly defined as &v4l2-buf-type;. Buffer types changed as
1585 mentioned above. A <structfield>field</structfield> field of type
1586 &v4l2-field; was added to indicate if a buffer contains a top or
1587 bottom field. The old field flags were removed. Since no unadjusted
1588 system time clock was added to the kernel as planned, the
1589 <structfield>timestamp</structfield> field changed back from type
1590 stamp_t, an unsigned 64 bit integer expressing the sample time in
1591 nanoseconds, to struct <structname>timeval</structname>. With the
1592 addition of a second memory mapping method the
1593 <structfield>offset</structfield> field moved into union
1594 <structfield>m</structfield>, and a new
1595 <structfield>memory</structfield> field of type &v4l2-memory; was
1596 added to distinguish between I/O methods. See <xref linkend="io" />
1599 <para>The <constant>V4L2_BUF_REQ_CONTIG</constant>
1600 flag was used by the V4L compatibility layer, after changes to this
1601 code it was no longer needed. The
1602 <constant>V4L2_BUF_ATTR_DEVICEMEM</constant> flag would indicate if
1603 the buffer was indeed allocated in device memory rather than DMA-able
1604 system memory. It was barely useful and so was removed.</para>
1608 <para>In &v4l2-framebuffer; the
1609 <structfield>base[3]</structfield> array anticipating double- and
1610 triple-buffering in off-screen video memory, however without defining
1611 a synchronization mechanism, was replaced by a single pointer. The
1612 <constant>V4L2_FBUF_CAP_SCALEUP</constant> and
1613 <constant>V4L2_FBUF_CAP_SCALEDOWN</constant> flags were removed.
1614 Applications can determine this capability more accurately using the
1615 new cropping and scaling interface. The
1616 <constant>V4L2_FBUF_CAP_CLIPPING</constant> flag was replaced by
1617 <constant>V4L2_FBUF_CAP_LIST_CLIPPING</constant> and
1618 <constant>V4L2_FBUF_CAP_BITMAP_CLIPPING</constant>.</para>
1622 <para>In &v4l2-clip; the <structfield>x</structfield>,
1623 <structfield>y</structfield>, <structfield>width</structfield> and
1624 <structfield>height</structfield> field moved into a
1625 <structfield>c</structfield> substructure of type &v4l2-rect;. The
1626 <structfield>x</structfield> and <structfield>y</structfield> fields
1627 were renamed to <structfield>left</structfield> and
1628 <structfield>top</structfield>, &ie; offsets to a context dependent
1633 <para>In &v4l2-window; the <structfield>x</structfield>,
1634 <structfield>y</structfield>, <structfield>width</structfield> and
1635 <structfield>height</structfield> field moved into a
1636 <structfield>w</structfield> substructure as above. A
1637 <structfield>field</structfield> field of type %v4l2-field; was added
1638 to distinguish between field and frame (interlaced) overlay.</para>
1642 <para>The digital zoom interface, including struct
1643 <structname>v4l2_zoomcap</structname>, struct
1644 <structname>v4l2_zoom</structname>,
1645 <constant>V4L2_ZOOM_NONCAP</constant> and
1646 <constant>V4L2_ZOOM_WHILESTREAMING</constant> was replaced by a new
1647 cropping and scaling interface. The previously unused struct
1648 <structname>v4l2_cropcap</structname> and
1649 <structname>v4l2_crop</structname> where redefined for this purpose.
1650 See <xref linkend="crop" /> for details.</para>
1654 <para>In &v4l2-vbi-format; the
1655 <structfield>SAMPLE_FORMAT</structfield> field now contains a
1656 four-character-code as used to identify video image formats and
1657 <constant>V4L2_PIX_FMT_GREY</constant> replaces the
1658 <constant>V4L2_VBI_SF_UBYTE</constant> define. The
1659 <structfield>reserved</structfield> field was extended.</para>
1663 <para>In &v4l2-captureparm; the type of the
1664 <structfield>timeperframe</structfield> field changed from unsigned
1665 long to &v4l2-fract;. This allows the accurate expression of multiples
1666 of the NTSC-M frame rate 30000 / 1001. A new field
1667 <structfield>readbuffers</structfield> was added to control the driver
1668 behaviour in read I/O mode.</para>
1670 <para>Similar changes were made to &v4l2-outputparm;.</para>
1674 <para>The struct <structname>v4l2_performance</structname>
1675 and <constant>VIDIOC_G_PERF</constant> ioctl were dropped. Except when
1676 using the <link linkend="rw">read/write I/O method</link>, which is
1677 limited anyway, this information is already available to
1678 applications.</para>
1682 <para>The example transformation from RGB to YCbCr color
1683 space in the old V4L2 documentation was inaccurate, this has been
1684 corrected in <xref linkend="pixfmt" />.<!-- 0.5670G should be
1685 0.587, and 127/112 != 255/224 --></para>
1691 <title>V4L2 2003-06-19</title>
1695 <para>A new capability flag
1696 <constant>V4L2_CAP_RADIO</constant> was added for radio devices. Prior
1697 to this change radio devices would identify solely by having exactly one
1698 tuner whose type field reads <constant>V4L2_TUNER_RADIO</constant>.</para>
1702 <para>An optional driver access priority mechanism was
1703 added, see <xref linkend="app-pri" /> for details.</para>
1707 <para>The audio input and output interface was found to be
1709 <para>Previously the &VIDIOC-G-AUDIO;
1710 ioctl would enumerate the available audio inputs. An ioctl to
1711 determine the current audio input, if more than one combines with the
1712 current video input, did not exist. So
1713 <constant>VIDIOC_G_AUDIO</constant> was renamed to
1714 <constant>VIDIOC_G_AUDIO_OLD</constant>, this ioctl was removed on
1715 Kernel 2.6.39. The &VIDIOC-ENUMAUDIO; ioctl was added to enumerate
1716 audio inputs, while &VIDIOC-G-AUDIO; now reports the current audio
1718 <para>The same changes were made to &VIDIOC-G-AUDOUT; and
1719 &VIDIOC-ENUMAUDOUT;.</para>
1720 <para>Until further the "videodev" module will automatically
1721 translate between the old and new ioctls, but drivers and applications
1722 must be updated to successfully compile again.</para>
1726 <para>The &VIDIOC-OVERLAY; ioctl was incorrectly defined with
1727 write-read parameter. It was changed to write-only, while the write-read
1728 version was renamed to <constant>VIDIOC_OVERLAY_OLD</constant>. The old
1729 ioctl was removed on Kernel 2.6.39. Until further the "videodev"
1730 kernel module will automatically translate to the new version, so drivers
1731 must be recompiled, but not applications.</para>
1735 <para><xref linkend="overlay" /> incorrectly stated that
1736 clipping rectangles define regions where the video can be seen.
1737 Correct is that clipping rectangles define regions where
1738 <emphasis>no</emphasis> video shall be displayed and so the graphics
1739 surface can be seen.</para>
1743 <para>The &VIDIOC-S-PARM; and &VIDIOC-S-CTRL; ioctls were
1744 defined with write-only parameter, inconsistent with other ioctls
1745 modifying their argument. They were changed to write-read, while a
1746 <constant>_OLD</constant> suffix was added to the write-only versions.
1747 The old ioctls were removed on Kernel 2.6.39. Drivers and
1748 applications assuming a constant parameter need an update.</para>
1754 <title>V4L2 2003-11-05</title>
1757 <para>In <xref linkend="pixfmt-rgb" /> the following pixel
1758 formats were incorrectly transferred from Bill Dirks' V4L2
1759 specification. Descriptions below refer to bytes in memory, in
1760 ascending address order.<informaltable>
1764 <entry>Symbol</entry>
1765 <entry>In this document prior to revision
1767 <entry>Corrected</entry>
1770 <tbody valign="top">
1772 <entry><constant>V4L2_PIX_FMT_RGB24</constant></entry>
1773 <entry>B, G, R</entry>
1774 <entry>R, G, B</entry>
1777 <entry><constant>V4L2_PIX_FMT_BGR24</constant></entry>
1778 <entry>R, G, B</entry>
1779 <entry>B, G, R</entry>
1782 <entry><constant>V4L2_PIX_FMT_RGB32</constant></entry>
1783 <entry>B, G, R, X</entry>
1784 <entry>R, G, B, X</entry>
1787 <entry><constant>V4L2_PIX_FMT_BGR32</constant></entry>
1788 <entry>R, G, B, X</entry>
1789 <entry>B, G, R, X</entry>
1793 </informaltable> The
1794 <constant>V4L2_PIX_FMT_BGR24</constant> example was always
1796 <para>In <xref linkend="v4l-image-properties" /> the mapping
1797 of the V4L <constant>VIDEO_PALETTE_RGB24</constant> and
1798 <constant>VIDEO_PALETTE_RGB32</constant> formats to V4L2 pixel formats
1799 was accordingly corrected.</para>
1803 <para>Unrelated to the fixes above, drivers may still
1804 interpret some V4L2 RGB pixel formats differently. These issues have
1805 yet to be addressed, for details see <xref
1806 linkend="pixfmt-rgb" />.</para>
1812 <title>V4L2 in Linux 2.6.6, 2004-05-09</title>
1815 <para>The &VIDIOC-CROPCAP; ioctl was incorrectly defined
1816 with read-only parameter. It is now defined as write-read ioctl, while
1817 the read-only version was renamed to
1818 <constant>VIDIOC_CROPCAP_OLD</constant>. The old ioctl was removed
1819 on Kernel 2.6.39.</para>
1825 <title>V4L2 in Linux 2.6.8</title>
1828 <para>A new field <structfield>input</structfield> (former
1829 <structfield>reserved[0]</structfield>) was added to the &v4l2-buffer;
1830 structure. Purpose of this field is to alternate between video inputs
1831 (⪚ cameras) in step with the video capturing process. This function
1832 must be enabled with the new <constant>V4L2_BUF_FLAG_INPUT</constant>
1833 flag. The <structfield>flags</structfield> field is no longer
1840 <title>V4L2 spec erratum 2004-08-01</title>
1844 <para>The return value of the
1845 <xref linkend="func-open" /> function was incorrectly documented.</para>
1849 <para>Audio output ioctls end in -AUDOUT, not -AUDIOOUT.</para>
1853 <para>In the Current Audio Input example the
1854 <constant>VIDIOC_G_AUDIO</constant> ioctl took the wrong
1859 <para>The documentation of the &VIDIOC-QBUF; and
1860 &VIDIOC-DQBUF; ioctls did not mention the &v4l2-buffer;
1861 <structfield>memory</structfield> field. It was also missing from
1862 examples. Also on the <constant>VIDIOC_DQBUF</constant> page the &EIO;
1863 was not documented.</para>
1869 <title>V4L2 in Linux 2.6.14</title>
1872 <para>A new sliced VBI interface was added. It is documented
1873 in <xref linkend="sliced" /> and replaces the interface first
1874 proposed in V4L2 specification 0.8.</para>
1880 <title>V4L2 in Linux 2.6.15</title>
1883 <para>The &VIDIOC-LOG-STATUS; ioctl was added.</para>
1887 <para>New video standards
1888 <constant>V4L2_STD_NTSC_443</constant>,
1889 <constant>V4L2_STD_SECAM_LC</constant>,
1890 <constant>V4L2_STD_SECAM_DK</constant> (a set of SECAM D, K and K1),
1891 and <constant>V4L2_STD_ATSC</constant> (a set of
1892 <constant>V4L2_STD_ATSC_8_VSB</constant> and
1893 <constant>V4L2_STD_ATSC_16_VSB</constant>) were defined. Note the
1894 <constant>V4L2_STD_525_60</constant> set now includes
1895 <constant>V4L2_STD_NTSC_443</constant>. See also <xref
1896 linkend="v4l2-std-id" />.</para>
1900 <para>The <constant>VIDIOC_G_COMP</constant> and
1901 <constant>VIDIOC_S_COMP</constant> ioctl were renamed to
1902 <constant>VIDIOC_G_MPEGCOMP</constant> and
1903 <constant>VIDIOC_S_MPEGCOMP</constant> respectively. Their argument
1904 was replaced by a struct
1905 <structname>v4l2_mpeg_compression</structname> pointer. (The
1906 <constant>VIDIOC_G_MPEGCOMP</constant> and
1907 <constant>VIDIOC_S_MPEGCOMP</constant> ioctls where removed in Linux
1914 <title>V4L2 spec erratum 2005-11-27</title>
1915 <para>The capture example in <xref linkend="capture-example" />
1916 called the &VIDIOC-S-CROP; ioctl without checking if cropping is
1917 supported. In the video standard selection example in
1918 <xref linkend="standard" /> the &VIDIOC-S-STD; call used the wrong
1919 argument type.</para>
1923 <title>V4L2 spec erratum 2006-01-10</title>
1926 <para>The <constant>V4L2_IN_ST_COLOR_KILL</constant> flag in
1927 &v4l2-input; not only indicates if the color killer is enabled, but
1928 also if it is active. (The color killer disables color decoding when
1929 it detects no color in the video signal to improve the image
1934 <para>&VIDIOC-S-PARM; is a write-read ioctl, not write-only as
1935 stated on its reference page. The ioctl changed in 2003 as noted above.</para>
1941 <title>V4L2 spec erratum 2006-02-03</title>
1944 <para>In &v4l2-captureparm; and &v4l2-outputparm; the
1945 <structfield>timeperframe</structfield> field gives the time in
1946 seconds, not microseconds.</para>
1952 <title>V4L2 spec erratum 2006-02-04</title>
1955 <para>The <structfield>clips</structfield> field in
1956 &v4l2-window; must point to an array of &v4l2-clip;, not a linked
1957 list, because drivers ignore the struct
1958 <structname>v4l2_clip</structname>.<structfield>next</structfield>
1965 <title>V4L2 in Linux 2.6.17</title>
1968 <para>New video standard macros were added:
1969 <constant>V4L2_STD_NTSC_M_KR</constant> (NTSC M South Korea), and the
1970 sets <constant>V4L2_STD_MN</constant>,
1971 <constant>V4L2_STD_B</constant>, <constant>V4L2_STD_GH</constant> and
1972 <constant>V4L2_STD_DK</constant>. The
1973 <constant>V4L2_STD_NTSC</constant> and
1974 <constant>V4L2_STD_SECAM</constant> sets now include
1975 <constant>V4L2_STD_NTSC_M_KR</constant> and
1976 <constant>V4L2_STD_SECAM_LC</constant> respectively.</para>
1980 <para>A new <constant>V4L2_TUNER_MODE_LANG1_LANG2</constant>
1981 was defined to record both languages of a bilingual program. The
1982 use of <constant>V4L2_TUNER_MODE_STEREO</constant> for this purpose
1983 is deprecated now. See the &VIDIOC-G-TUNER; section for
1990 <title>V4L2 spec erratum 2006-09-23 (Draft 0.15)</title>
1993 <para>In various places
1994 <constant>V4L2_BUF_TYPE_SLICED_VBI_CAPTURE</constant> and
1995 <constant>V4L2_BUF_TYPE_SLICED_VBI_OUTPUT</constant> of the sliced VBI
1996 interface were not mentioned along with other buffer types.</para>
2000 <para>In <xref linkend="vidioc-g-audio" /> it was clarified
2001 that the &v4l2-audio; <structfield>mode</structfield> field is a flags
2006 <para><xref linkend="vidioc-querycap" /> did not mention the
2007 sliced VBI and radio capability flags.</para>
2011 <para>In <xref linkend="vidioc-g-frequency" /> it was
2012 clarified that applications must initialize the tuner
2013 <structfield>type</structfield> field of &v4l2-frequency; before
2014 calling &VIDIOC-S-FREQUENCY;.</para>
2018 <para>The <structfield>reserved</structfield> array
2019 in &v4l2-requestbuffers; has 2 elements, not 32.</para>
2023 <para>In <xref linkend="output" /> and <xref
2024 linkend="raw-vbi" /> the device file names
2025 <filename>/dev/vout</filename> which never caught on were replaced
2026 by <filename>/dev/video</filename>.</para>
2030 <para>With Linux 2.6.15 the possible range for VBI device minor
2031 numbers was extended from 224-239 to 224-255. Accordingly device file names
2032 <filename>/dev/vbi0</filename> to <filename>/dev/vbi31</filename> are
2033 possible now.</para>
2039 <title>V4L2 in Linux 2.6.18</title>
2042 <para>New ioctls &VIDIOC-G-EXT-CTRLS;, &VIDIOC-S-EXT-CTRLS;
2043 and &VIDIOC-TRY-EXT-CTRLS; were added, a flag to skip unsupported
2044 controls with &VIDIOC-QUERYCTRL;, new control types
2045 <constant>V4L2_CTRL_TYPE_INTEGER64</constant> and
2046 <constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant> (<xref
2047 linkend="v4l2-ctrl-type" />), and new control flags
2048 <constant>V4L2_CTRL_FLAG_READ_ONLY</constant>,
2049 <constant>V4L2_CTRL_FLAG_UPDATE</constant>,
2050 <constant>V4L2_CTRL_FLAG_INACTIVE</constant> and
2051 <constant>V4L2_CTRL_FLAG_SLIDER</constant> (<xref
2052 linkend="control-flags" />). See <xref
2053 linkend="extended-controls" /> for details.</para>
2059 <title>V4L2 in Linux 2.6.19</title>
2062 <para>In &v4l2-sliced-vbi-cap; a buffer type field was added
2063 replacing a reserved field. Note on architectures where the size of
2064 enum types differs from int types the size of the structure changed.
2065 The &VIDIOC-G-SLICED-VBI-CAP; ioctl was redefined from being read-only
2066 to write-read. Applications must initialize the type field and clear
2067 the reserved fields now. These changes may <emphasis>break the
2068 compatibility</emphasis> with older drivers and applications.</para>
2072 <para>The ioctls &VIDIOC-ENUM-FRAMESIZES; and
2073 &VIDIOC-ENUM-FRAMEINTERVALS; were added.</para>
2077 <para>A new pixel format <constant>V4L2_PIX_FMT_RGB444</constant> (<xref
2078 linkend="rgb-formats" />) was added.</para>
2084 <title>V4L2 spec erratum 2006-10-12 (Draft 0.17)</title>
2087 <para><constant>V4L2_PIX_FMT_HM12</constant> (<xref
2088 linkend="reserved-formats" />) is a YUV 4:2:0, not 4:2:2 format.</para>
2094 <title>V4L2 in Linux 2.6.21</title>
2097 <para>The <filename>videodev2.h</filename> header file is
2098 now dual licensed under GNU General Public License version two or
2099 later, and under a 3-clause BSD-style license.</para>
2105 <title>V4L2 in Linux 2.6.22</title>
2108 <para>Two new field orders
2109 <constant>V4L2_FIELD_INTERLACED_TB</constant> and
2110 <constant>V4L2_FIELD_INTERLACED_BT</constant> were
2111 added. See <xref linkend="v4l2-field" /> for details.</para>
2115 <para>Three new clipping/blending methods with a global or
2116 straight or inverted local alpha value were added to the video overlay
2117 interface. See the description of the &VIDIOC-G-FBUF; and
2118 &VIDIOC-S-FBUF; ioctls for details.</para>
2119 <para>A new <structfield>global_alpha</structfield> field
2121 linkend="v4l2-window"><structname>v4l2_window</structname></link>,
2122 extending the structure. This may <emphasis>break
2123 compatibility</emphasis> with applications using a struct
2124 <structname>v4l2_window</structname> directly. However the <link
2125 linkend="vidioc-g-fmt">VIDIOC_G/S/TRY_FMT</link> ioctls, which take a
2126 pointer to a <link linkend="v4l2-format">v4l2_format</link> parent
2127 structure with padding bytes at the end, are not affected.</para>
2131 <para>The format of the <structfield>chromakey</structfield>
2132 field in &v4l2-window; changed from "host order RGB32" to a pixel
2133 value in the same format as the framebuffer. This may <emphasis>break
2134 compatibility</emphasis> with existing applications. Drivers
2135 supporting the "host order RGB32" format are not known.</para>
2142 <title>V4L2 in Linux 2.6.24</title>
2145 <para>The pixel formats
2146 <constant>V4L2_PIX_FMT_PAL8</constant>,
2147 <constant>V4L2_PIX_FMT_YUV444</constant>,
2148 <constant>V4L2_PIX_FMT_YUV555</constant>,
2149 <constant>V4L2_PIX_FMT_YUV565</constant> and
2150 <constant>V4L2_PIX_FMT_YUV32</constant> were added.</para>
2156 <title>V4L2 in Linux 2.6.25</title>
2159 <para>The pixel formats <link linkend="V4L2-PIX-FMT-Y16">
2160 <constant>V4L2_PIX_FMT_Y16</constant></link> and <link
2161 linkend="V4L2-PIX-FMT-SBGGR16">
2162 <constant>V4L2_PIX_FMT_SBGGR16</constant></link> were added.</para>
2165 <para>New <link linkend="control">controls</link>
2166 <constant>V4L2_CID_POWER_LINE_FREQUENCY</constant>,
2167 <constant>V4L2_CID_HUE_AUTO</constant>,
2168 <constant>V4L2_CID_WHITE_BALANCE_TEMPERATURE</constant>,
2169 <constant>V4L2_CID_SHARPNESS</constant> and
2170 <constant>V4L2_CID_BACKLIGHT_COMPENSATION</constant> were added. The
2171 controls <constant>V4L2_CID_BLACK_LEVEL</constant>,
2172 <constant>V4L2_CID_WHITENESS</constant>,
2173 <constant>V4L2_CID_HCENTER</constant> and
2174 <constant>V4L2_CID_VCENTER</constant> were deprecated.
2178 <para>A <link linkend="camera-controls">Camera controls
2179 class</link> was added, with the new controls
2180 <constant>V4L2_CID_EXPOSURE_AUTO</constant>,
2181 <constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>,
2182 <constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>,
2183 <constant>V4L2_CID_PAN_RELATIVE</constant>,
2184 <constant>V4L2_CID_TILT_RELATIVE</constant>,
2185 <constant>V4L2_CID_PAN_RESET</constant>,
2186 <constant>V4L2_CID_TILT_RESET</constant>,
2187 <constant>V4L2_CID_PAN_ABSOLUTE</constant>,
2188 <constant>V4L2_CID_TILT_ABSOLUTE</constant>,
2189 <constant>V4L2_CID_FOCUS_ABSOLUTE</constant>,
2190 <constant>V4L2_CID_FOCUS_RELATIVE</constant> and
2191 <constant>V4L2_CID_FOCUS_AUTO</constant>.</para>
2194 <para>The <constant>VIDIOC_G_MPEGCOMP</constant> and
2195 <constant>VIDIOC_S_MPEGCOMP</constant> ioctls, which were superseded
2196 by the <link linkend="extended-controls">extended controls</link>
2197 interface in Linux 2.6.18, where finally removed from the
2198 <filename>videodev2.h</filename> header file.</para>
2204 <title>V4L2 in Linux 2.6.26</title>
2207 <para>The pixel formats
2208 <constant>V4L2_PIX_FMT_Y16</constant> and
2209 <constant>V4L2_PIX_FMT_SBGGR16</constant> were added.</para>
2212 <para>Added user controls
2213 <constant>V4L2_CID_CHROMA_AGC</constant> and
2214 <constant>V4L2_CID_COLOR_KILLER</constant>.</para>
2220 <title>V4L2 in Linux 2.6.27</title>
2223 <para>The &VIDIOC-S-HW-FREQ-SEEK; ioctl and the
2224 <constant>V4L2_CAP_HW_FREQ_SEEK</constant> capability were added.</para>
2227 <para>The pixel formats
2228 <constant>V4L2_PIX_FMT_YVYU</constant>,
2229 <constant>V4L2_PIX_FMT_PCA501</constant>,
2230 <constant>V4L2_PIX_FMT_PCA505</constant>,
2231 <constant>V4L2_PIX_FMT_PCA508</constant>,
2232 <constant>V4L2_PIX_FMT_PCA561</constant>,
2233 <constant>V4L2_PIX_FMT_SGBRG8</constant>,
2234 <constant>V4L2_PIX_FMT_PAC207</constant> and
2235 <constant>V4L2_PIX_FMT_PJPG</constant> were added.</para>
2241 <title>V4L2 in Linux 2.6.28</title>
2244 <para>Added <constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant> and
2245 <constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant> MPEG audio encodings.</para>
2248 <para>Added <constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant> MPEG
2249 video encoding.</para>
2252 <para>The pixel formats
2253 <constant>V4L2_PIX_FMT_SGRBG10</constant> and
2254 <constant>V4L2_PIX_FMT_SGRBG10DPCM8</constant> were added.</para>
2260 <title>V4L2 in Linux 2.6.29</title>
2263 <para>The <constant>VIDIOC_G_CHIP_IDENT</constant> ioctl was renamed
2264 to <constant>VIDIOC_G_CHIP_IDENT_OLD</constant> and &VIDIOC-DBG-G-CHIP-IDENT;
2265 was introduced in its place. The old struct <structname>v4l2_chip_ident</structname>
2266 was renamed to <structname id="v4l2-chip-ident-old">v4l2_chip_ident_old</structname>.</para>
2269 <para>The pixel formats
2270 <constant>V4L2_PIX_FMT_VYUY</constant>,
2271 <constant>V4L2_PIX_FMT_NV16</constant> and
2272 <constant>V4L2_PIX_FMT_NV61</constant> were added.</para>
2275 <para>Added camera controls
2276 <constant>V4L2_CID_ZOOM_ABSOLUTE</constant>,
2277 <constant>V4L2_CID_ZOOM_RELATIVE</constant>,
2278 <constant>V4L2_CID_ZOOM_CONTINUOUS</constant> and
2279 <constant>V4L2_CID_PRIVACY</constant>.</para>
2284 <title>V4L2 in Linux 2.6.30</title>
2287 <para>New control flag <constant>V4L2_CTRL_FLAG_WRITE_ONLY</constant> was added.</para>
2290 <para>New control <constant>V4L2_CID_COLORFX</constant> was added.</para>
2295 <title>V4L2 in Linux 2.6.32</title>
2298 <para>In order to be easier to compare a V4L2 API and a kernel
2299 version, now V4L2 API is numbered using the Linux Kernel version numeration.</para>
2302 <para>Finalized the RDS capture API. See <xref linkend="rds" /> for
2303 more information.</para>
2306 <para>Added new capabilities for modulators and RDS encoders.</para>
2309 <para>Add description for libv4l API.</para>
2312 <para>Added support for string controls via new type <constant>V4L2_CTRL_TYPE_STRING</constant>.</para>
2315 <para>Added <constant>V4L2_CID_BAND_STOP_FILTER</constant> documentation.</para>
2318 <para>Added FM Modulator (FM TX) Extended Control Class: <constant>V4L2_CTRL_CLASS_FM_TX</constant> and their Control IDs.</para>
2321 <para>Added Remote Controller chapter, describing the default Remote Controller mapping for media devices.</para>
2326 <title>V4L2 in Linux 2.6.33</title>
2329 <para>Added support for Digital Video timings in order to support HDTV receivers and transmitters.</para>
2334 <title>V4L2 in Linux 2.6.34</title>
2338 <constant>V4L2_CID_IRIS_ABSOLUTE</constant> and
2339 <constant>V4L2_CID_IRIS_RELATIVE</constant> controls to the
2340 <link linkend="camera-controls">Camera controls class</link>.
2346 <title>V4L2 in Linux 2.6.37</title>
2349 <para>Remove the vtx (videotext/teletext) API. This API was no longer
2350 used and no hardware exists to verify the API. Nor were any userspace applications found
2351 that used it. It was originally scheduled for removal in 2.6.35.
2357 <title>V4L2 in Linux 2.6.39</title>
2360 <para>The old VIDIOC_*_OLD symbols and V4L1 support were removed.</para>
2363 <para>Multi-planar API added. Does not affect the compatibility of
2364 current drivers and applications. See
2365 <link linkend="planar-apis">multi-planar API</link>
2371 <section id="other">
2372 <title>Relation of V4L2 to other Linux multimedia APIs</title>
2374 <section id="xvideo">
2375 <title>X Video Extension</title>
2377 <para>The X Video Extension (abbreviated XVideo or just Xv) is
2378 an extension of the X Window system, implemented for example by the
2379 XFree86 project. Its scope is similar to V4L2, an API to video capture
2380 and output devices for X clients. Xv allows applications to display
2381 live video in a window, send window contents to a TV output, and
2382 capture or output still images in XPixmaps<footnote>
2383 <para>This is not implemented in XFree86.</para>
2384 </footnote>. With their implementation XFree86 makes the
2385 extension available across many operating systems and
2386 architectures.</para>
2388 <para>Because the driver is embedded into the X server Xv has a
2389 number of advantages over the V4L2 <link linkend="overlay">video
2390 overlay interface</link>. The driver can easily determine the overlay
2391 target, &ie; visible graphics memory or off-screen buffers for a
2392 destructive overlay. It can program the RAMDAC for a non-destructive
2393 overlay, scaling or color-keying, or the clipping functions of the
2394 video capture hardware, always in sync with drawing operations or
2395 windows moving or changing their stacking order.</para>
2397 <para>To combine the advantages of Xv and V4L a special Xv
2398 driver exists in XFree86 and XOrg, just programming any overlay capable
2399 Video4Linux device it finds. To enable it
2400 <filename>/etc/X11/XF86Config</filename> must contain these lines:</para>
2404 EndSection</screen></para>
2406 <para>As of XFree86 4.2 this driver still supports only V4L
2407 ioctls, however it should work just fine with all V4L2 devices through
2408 the V4L2 backward-compatibility layer. Since V4L2 permits multiple
2409 opens it is possible (if supported by the V4L2 driver) to capture
2410 video while an X client requested video overlay. Restrictions of
2411 simultaneous capturing and overlay are discussed in <xref
2412 linkend="overlay" /> apply.</para>
2414 <para>Only marginally related to V4L2, XFree86 extended Xv to
2415 support hardware YUV to RGB conversion and scaling for faster video
2416 playback, and added an interface to MPEG-2 decoding hardware. This API
2417 is useful to display images captured with V4L2 devices.</para>
2421 <title>Digital Video</title>
2423 <para>V4L2 does not support digital terrestrial, cable or
2424 satellite broadcast. A separate project aiming at digital receivers
2425 exists. You can find its homepage at <ulink
2426 url="http://linuxtv.org">http://linuxtv.org</ulink>. The Linux DVB API
2427 has no connection to the V4L2 API except that drivers for hybrid
2428 hardware may support both.</para>
2432 <title>Audio Interfaces</title>
2434 <para>[to do - OSS/ALSA]</para>
2438 <section id="experimental">
2439 <title>Experimental API Elements</title>
2441 <para>The following V4L2 API elements are currently experimental
2442 and may change in the future.</para>
2446 <para>Video Output Overlay (OSD) Interface, <xref
2447 linkend="osd" />.</para>
2450 <para><constant>V4L2_BUF_TYPE_VIDEO_OUTPUT_OVERLAY</constant>,
2451 &v4l2-buf-type;, <xref linkend="v4l2-buf-type" />.</para>
2454 <para><constant>V4L2_CAP_VIDEO_OUTPUT_OVERLAY</constant>,
2455 &VIDIOC-QUERYCAP; ioctl, <xref linkend="device-capabilities" />.</para>
2458 <para>&VIDIOC-ENUM-FRAMESIZES; and
2459 &VIDIOC-ENUM-FRAMEINTERVALS; ioctls.</para>
2462 <para>&VIDIOC-G-ENC-INDEX; ioctl.</para>
2465 <para>&VIDIOC-ENCODER-CMD; and &VIDIOC-TRY-ENCODER-CMD;
2469 <para>&VIDIOC-DBG-G-REGISTER; and &VIDIOC-DBG-S-REGISTER;
2473 <para>&VIDIOC-DBG-G-CHIP-IDENT; ioctl.</para>
2478 <section id="obsolete">
2479 <title>Obsolete API Elements</title>
2481 <para>The following V4L2 API elements were superseded by new
2482 interfaces and should not be implemented in new drivers.</para>
2486 <para><constant>VIDIOC_G_MPEGCOMP</constant> and
2487 <constant>VIDIOC_S_MPEGCOMP</constant> ioctls. Use Extended Controls,
2488 <xref linkend="extended-controls" />.</para>
2497 sgml-parent-document: "v4l2.sgml"
2498 indent-tabs-mode: nil
git.openpandora.org / pandora-kernel.git / blob