1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
5 ***********************
6 Changes of the V4L2 API
7 ***********************
9 Soon after the V4L API was added to the kernel it was criticised as too
10 inflexible. In August 1998 Bill Dirks proposed a number of improvements
11 and began to work on documentation, example drivers and applications.
12 With the help of other volunteers this eventually became the V4L2 API,
13 not just an extension but a replacement for the V4L API. However it took
14 another four years and two stable kernel releases until the new API was
15 finally accepted for inclusion into the kernel in its present form.
21 1998-08-20: First version.
23 1998-08-27: The :ref:`select() <func-select>` function was introduced.
25 1998-09-10: New video standard interface.
27 1998-09-18: The ``VIDIOC_NONCAP`` ioctl was replaced by the otherwise
28 meaningless ``O_TRUNC`` :ref:`open() <func-open>` flag, and the
29 aliases ``O_NONCAP`` and ``O_NOIO`` were defined. Applications can set
30 this flag if they intend to access controls only, as opposed to capture
31 applications which need exclusive access. The ``VIDEO_STD_XXX``
32 identifiers are now ordinals instead of flags, and the
33 ``video_std_construct()`` helper function takes id and
34 transmission arguments.
36 1998-09-28: Revamped video standard. Made video controls individually
39 1998-10-02: The ``id`` field was removed from
40 struct ``video_standard`` and the color subcarrier fields were
41 renamed. The :ref:`VIDIOC_QUERYSTD` ioctl was
42 renamed to :ref:`VIDIOC_ENUMSTD`,
43 :ref:`VIDIOC_G_INPUT <VIDIOC_G_INPUT>` to
44 :ref:`VIDIOC_ENUMINPUT`. A first draft of the
45 Codec API was released.
47 1998-11-08: Many minor changes. Most symbols have been renamed. Some
48 material changes to struct v4l2_capability.
50 1998-11-12: The read/write directon of some ioctls was misdefined.
52 1998-11-14: ``V4L2_PIX_FMT_RGB24`` changed to ``V4L2_PIX_FMT_BGR24``,
53 and ``V4L2_PIX_FMT_RGB32`` changed to ``V4L2_PIX_FMT_BGR32``. Audio
54 controls are now accessible with the
55 :ref:`VIDIOC_G_CTRL <VIDIOC_G_CTRL>` and
56 :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls under names starting
57 with ``V4L2_CID_AUDIO``. The ``V4L2_MAJOR`` define was removed from
58 ``videodev.h`` since it was only used once in the ``videodev`` kernel
59 module. The ``YUV422`` and ``YUV411`` planar image formats were added.
61 1998-11-28: A few ioctl symbols changed. Interfaces for codecs and video
62 output devices were added.
64 1999-01-14: A raw VBI capture interface was added.
66 1999-01-19: The ``VIDIOC_NEXTBUF`` ioctl was removed.
69 V4L2 Version 0.16 1999-01-31
70 ============================
72 1999-01-27: There is now one QBUF ioctl, VIDIOC_QWBUF and VIDIOC_QRBUF
73 are gone. VIDIOC_QBUF takes a v4l2_buffer as a parameter. Added
74 digital zoom (cropping) controls.
77 V4L2 Version 0.18 1999-03-16
78 ============================
80 Added a v4l to V4L2 ioctl compatibility layer to videodev.c. Driver
81 writers, this changes how you implement your ioctl handler. See the
82 Driver Writer's Guide. Added some more control id codes.
85 V4L2 Version 0.19 1999-06-05
86 ============================
88 1999-03-18: Fill in the category and catname fields of v4l2_queryctrl
89 objects before passing them to the driver. Required a minor change to
90 the VIDIOC_QUERYCTRL handlers in the sample drivers.
92 1999-03-31: Better compatibility for v4l memory capture ioctls. Requires
93 changes to drivers to fully support new compatibility features, see
94 Driver Writer's Guide and v4l2cap.c. Added new control IDs:
95 V4L2_CID_HFLIP, _VFLIP. Changed V4L2_PIX_FMT_YUV422P to _YUV422P,
96 and _YUV411P to _YUV411P.
98 1999-04-04: Added a few more control IDs.
100 1999-04-07: Added the button control type.
102 1999-05-02: Fixed a typo in videodev.h, and added the
103 V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag.
105 1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing a
106 malfunction of this ioctl.
108 1999-06-05: Changed the value of V4L2_CID_WHITENESS.
111 V4L2 Version 0.20 (1999-09-10)
112 ==============================
114 Version 0.20 introduced a number of changes which were *not backward
115 compatible* with 0.19 and earlier versions. Purpose of these changes was
116 to simplify the API, while making it more extensible and following
117 common Linux driver API conventions.
119 1. Some typos in ``V4L2_FMT_FLAG`` symbols were fixed. struct v4l2_clip
120 was changed for compatibility with v4l. (1999-08-30)
122 2. ``V4L2_TUNER_SUB_LANG1`` was added. (1999-09-05)
124 3. All ioctl() commands that used an integer argument now take a pointer
125 to an integer. Where it makes sense, ioctls will return the actual
126 new value in the integer pointed to by the argument, a common
127 convention in the V4L2 API. The affected ioctls are: VIDIOC_PREVIEW,
128 VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ,
129 VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example
134 err = ioctl (fd, VIDIOC_XXX, V4L2_XXX);
141 int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a);
143 4. All the different get- and set-format commands were swept into one
144 :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
145 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl taking a union and a
146 type field selecting the union member as parameter. Purpose is to
147 simplify the API by eliminating several ioctls and to allow new and
148 driver private data streams without adding new ioctls.
150 This change obsoletes the following ioctls: ``VIDIOC_S_INFMT``,
151 ``VIDIOC_G_INFMT``, ``VIDIOC_S_OUTFMT``, ``VIDIOC_G_OUTFMT``,
152 ``VIDIOC_S_VBIFMT`` and ``VIDIOC_G_VBIFMT``. The image format
153 struct v4l2_format was renamed to struct v4l2_pix_format, while
154 struct v4l2_format is now the envelopping structure
155 for all format negotiations.
157 5. Similar to the changes above, the ``VIDIOC_G_PARM`` and
158 ``VIDIOC_S_PARM`` ioctls were merged with ``VIDIOC_G_OUTPARM`` and
159 ``VIDIOC_S_OUTPARM``. A ``type`` field in the new struct v4l2_streamparm
160 selects the respective union member.
162 This change obsoletes the ``VIDIOC_G_OUTPARM`` and
163 ``VIDIOC_S_OUTPARM`` ioctls.
165 6. Control enumeration was simplified, and two new control flags were
166 introduced and one dropped. The ``catname`` field was replaced by a
169 Drivers can now flag unsupported and temporarily unavailable controls
170 with ``V4L2_CTRL_FLAG_DISABLED`` and ``V4L2_CTRL_FLAG_GRABBED``
171 respectively. The ``group`` name indicates a possibly narrower
172 classification than the ``category``. In other words, there may be
173 multiple groups within a category. Controls within a group would
174 typically be drawn within a group box. Controls in different
175 categories might have a greater separation, or may even appear in
178 7. The struct v4l2_buffer ``timestamp`` was
179 changed to a 64 bit integer, containing the sampling or output time
180 of the frame in nanoseconds. Additionally timestamps will be in
181 absolute system time, not starting from zero at the beginning of a
182 stream. The data type name for timestamps is stamp_t, defined as a
183 signed 64-bit integer. Output devices should not send a buffer out
184 until the time in the timestamp field has arrived. I would like to
185 follow SGI's lead, and adopt a multimedia timestamping system like
186 their UST (Unadjusted System Time). See
187 http://web.archive.org/web/\*/http://reality.sgi.com
188 /cpirazzi_engr/lg/time/intro.html. UST uses timestamps that are
189 64-bit signed integers (not struct timeval's) and given in nanosecond
190 units. The UST clock starts at zero when the system is booted and
191 runs continuously and uniformly. It takes a little over 292 years for
192 UST to overflow. There is no way to set the UST clock. The regular
193 Linux time-of-day clock can be changed periodically, which would
194 cause errors if it were being used for timestamping a multimedia
195 stream. A real UST style clock will require some support in the
196 kernel that is not there yet. But in anticipation, I will change the
197 timestamp field to a 64-bit integer, and I will change the
198 v4l2_masterclock_gettime() function (used only by drivers) to
199 return a 64-bit integer.
201 8. A ``sequence`` field was added to struct v4l2_buffer. The ``sequence``
202 field counts captured frames, it is ignored by output devices. When a
203 capture driver drops a frame, the sequence number of that frame is skipped.
206 V4L2 Version 0.20 incremental changes
207 =====================================
209 1999-12-23: In struct v4l2_vbi_format the
210 ``reserved1`` field became ``offset``. Previously drivers were required
211 to clear the ``reserved1`` field.
213 2000-01-13: The ``V4L2_FMT_FLAG_NOT_INTERLACED`` flag was added.
215 2000-07-31: The ``linux/poll.h`` header is now included by
216 ``videodev.h`` for compatibility with the original ``videodev.h`` file.
218 2000-11-20: ``V4L2_TYPE_VBI_OUTPUT`` and ``V4L2_PIX_FMT_Y41P`` were
221 2000-11-25: ``V4L2_TYPE_VBI_INPUT`` was added.
223 2000-12-04: A couple typos in symbol names were fixed.
225 2001-01-18: To avoid namespace conflicts the ``fourcc`` macro defined in
226 the ``videodev.h`` header file was renamed to ``v4l2_fourcc``.
228 2001-01-25: A possible driver-level compatibility problem between the
229 ``videodev.h`` file in Linux 2.4.0 and the ``videodev.h`` file included
230 in the ``videodevX`` patch was fixed. Users of an earlier version of
231 ``videodevX`` on Linux 2.4.0 should recompile their V4L and V4L2
234 2001-01-26: A possible kernel-level incompatibility between the
235 ``videodev.h`` file in the ``videodevX`` patch and the ``videodev.h``
236 file in Linux 2.2.x with devfs patches applied was fixed.
238 2001-03-02: Certain V4L ioctls which pass data in both direction
239 although they are defined with read-only parameter, did not work
240 correctly through the backward compatibility layer. [Solution?]
242 2001-04-13: Big endian 16-bit RGB formats were added.
244 2001-09-17: New YUV formats and the
245 :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
246 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctls were added.
247 (The old ``VIDIOC_G_FREQ`` and ``VIDIOC_S_FREQ`` ioctls did not take
248 multiple tuners into account.)
250 2000-09-18: ``V4L2_BUF_TYPE_VBI`` was added. This may *break
251 compatibility* as the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
252 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls may fail now if the
253 struct ``v4l2_fmt`` ``type`` field does not contain
254 ``V4L2_BUF_TYPE_VBI``. In the documentation of the struct v4l2_vbi_format`,
255 the ``offset`` field the ambiguous phrase "rising edge" was changed to
258 V4L2 Version 0.20 2000-11-23
259 ============================
261 A number of changes were made to the raw VBI interface.
263 1. Figures clarifying the line numbering scheme were added to the V4L2
264 API specification. The ``start``\ [0] and ``start``\ [1] fields no
265 longer count line numbers beginning at zero. Rationale: a) The
266 previous definition was unclear. b) The ``start``\ [] values are
267 ordinal numbers. c) There is no point in inventing a new line
268 numbering scheme. We now use line number as defined by ITU-R, period.
269 Compatibility: Add one to the start values. Applications depending on
270 the previous semantics may not function correctly.
272 2. The restriction "count[0] > 0 and count[1] > 0" has been relaxed to
273 "(count[0] + count[1]) > 0". Rationale: Drivers may allocate
274 resources at scan line granularity and some data services are
275 transmitted only on the first field. The comment that both ``count``
276 values will usually be equal is misleading and pointless and has been
277 removed. This change *breaks compatibility* with earlier versions:
278 Drivers may return ``EINVAL``, applications may not function correctly.
280 3. Drivers are again permitted to return negative (unknown) start values
281 as proposed earlier. Why this feature was dropped is unclear. This
282 change may *break compatibility* with applications depending on the
283 start values being positive. The use of ``EBUSY`` and ``EINVAL``
284 error codes with the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl was
285 clarified. The ``EBUSY`` error code was finally documented, and the
286 ``reserved2`` field which was previously mentioned only in the
287 ``videodev.h`` header file.
289 4. New buffer types ``V4L2_TYPE_VBI_INPUT`` and ``V4L2_TYPE_VBI_OUTPUT``
290 were added. The former is an alias for the old ``V4L2_TYPE_VBI``, the
291 latter was missing in the ``videodev.h`` file.
294 V4L2 Version 0.20 2002-07-25
295 ============================
297 Added sliced VBI interface proposal.
300 V4L2 in Linux 2.5.46, 2002-10
301 =============================
303 Around October-November 2002, prior to an announced feature freeze of
304 Linux 2.5, the API was revised, drawing from experience with V4L2 0.20.
305 This unnamed version was finally merged into Linux 2.5.46.
307 1. As specified in :ref:`related`, drivers must make related device
308 functions available under all minor device numbers.
310 2. The :ref:`open() <func-open>` function requires access mode
311 ``O_RDWR`` regardless of the device type. All V4L2 drivers
312 exchanging data with applications must support the ``O_NONBLOCK``
313 flag. The ``O_NOIO`` flag, a V4L2 symbol which aliased the
314 meaningless ``O_TRUNC`` to indicate accesses without data exchange
315 (panel applications) was dropped. Drivers must stay in "panel mode"
316 until the application attempts to initiate a data exchange, see
319 3. The struct v4l2_capability changed
320 dramatically. Note that also the size of the structure changed,
321 which is encoded in the ioctl request code, thus older V4L2 devices
322 will respond with an ``EINVAL`` error code to the new
323 :ref:`VIDIOC_QUERYCAP` ioctl.
325 There are new fields to identify the driver, a new RDS device
326 function ``V4L2_CAP_RDS_CAPTURE``, the ``V4L2_CAP_AUDIO`` flag
327 indicates if the device has any audio connectors, another I/O
328 capability ``V4L2_CAP_ASYNCIO`` can be flagged. In response to these
329 changes the ``type`` field became a bit set and was merged into the
330 ``flags`` field. ``V4L2_FLAG_TUNER`` was renamed to
331 ``V4L2_CAP_TUNER``, ``V4L2_CAP_VIDEO_OVERLAY`` replaced
332 ``V4L2_FLAG_PREVIEW`` and ``V4L2_CAP_VBI_CAPTURE`` and
333 ``V4L2_CAP_VBI_OUTPUT`` replaced ``V4L2_FLAG_DATA_SERVICE``.
334 ``V4L2_FLAG_READ`` and ``V4L2_FLAG_WRITE`` were merged into
335 ``V4L2_CAP_READWRITE``.
337 The redundant fields ``inputs``, ``outputs`` and ``audios`` were
338 removed. These properties can be determined as described in
339 :ref:`video` and :ref:`audio`.
341 The somewhat volatile and therefore barely useful fields
342 ``maxwidth``, ``maxheight``, ``minwidth``, ``minheight``,
343 ``maxframerate`` were removed. This information is available as
344 described in :ref:`format` and :ref:`standard`.
346 ``V4L2_FLAG_SELECT`` was removed. We believe the select() function
347 is important enough to require support of it in all V4L2 drivers
348 exchanging data with applications. The redundant
349 ``V4L2_FLAG_MONOCHROME`` flag was removed, this information is
350 available as described in :ref:`format`.
352 4. In struct v4l2_input the ``assoc_audio``
353 field and the ``capability`` field and its only flag
354 ``V4L2_INPUT_CAP_AUDIO`` was replaced by the new ``audioset`` field.
355 Instead of linking one video input to one audio input this field
356 reports all audio inputs this video input combines with.
358 New fields are ``tuner`` (reversing the former link from tuners to
359 video inputs), ``std`` and ``status``.
361 Accordingly struct v4l2_output lost its
362 ``capability`` and ``assoc_audio`` fields. ``audioset``,
363 ``modulator`` and ``std`` where added instead.
365 5. The struct v4l2_audio field ``audio`` was
366 renamed to ``index``, for consistency with other structures. A new
367 capability flag ``V4L2_AUDCAP_STEREO`` was added to indicated if the
368 audio input in question supports stereo sound.
369 ``V4L2_AUDCAP_EFFECTS`` and the corresponding ``V4L2_AUDMODE`` flags
370 where removed. This can be easily implemented using controls.
371 (However the same applies to AVL which is still there.)
373 Again for consistency the struct v4l2_audioout field ``audio`` was renamed
376 6. The struct v4l2_tuner ``input`` field was
377 replaced by an ``index`` field, permitting devices with multiple
378 tuners. The link between video inputs and tuners is now reversed,
379 inputs point to their tuner. The ``std`` substructure became a
380 simple set (more about this below) and moved into struct v4l2_input.
381 A ``type`` field was added.
383 Accordingly in struct v4l2_modulator the
384 ``output`` was replaced by an ``index`` field.
386 In struct v4l2_frequency the ``port``
387 field was replaced by a ``tuner`` field containing the respective
388 tuner or modulator index number. A tuner ``type`` field was added
389 and the ``reserved`` field became larger for future extensions
390 (satellite tuners in particular).
392 7. The idea of completely transparent video standards was dropped.
393 Experience showed that applications must be able to work with video
394 standards beyond presenting the user a menu. Instead of enumerating
395 supported standards with an ioctl applications can now refer to
396 standards by :ref:`v4l2_std_id <v4l2-std-id>` and symbols
397 defined in the ``videodev2.h`` header file. For details see
398 :ref:`standard`. The :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` and
399 :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` now take a pointer to this
400 type as argument. :ref:`VIDIOC_QUERYSTD` was
401 added to autodetect the received standard, if the hardware has this
402 capability. In struct v4l2_standard an
403 ``index`` field was added for
404 :ref:`VIDIOC_ENUMSTD`. A
405 :ref:`v4l2_std_id <v4l2-std-id>` field named ``id`` was added as
406 machine readable identifier, also replacing the ``transmission``
407 field. The misleading ``framerate`` field was renamed to
408 ``frameperiod``. The now obsolete ``colorstandard`` information,
409 originally needed to distguish between variations of standards, were
412 Struct ``v4l2_enumstd`` ceased to be.
413 :ref:`VIDIOC_ENUMSTD` now takes a pointer to a
414 struct v4l2_standard directly. The
415 information which standards are supported by a particular video
416 input or output moved into struct v4l2_input
417 and struct v4l2_output fields named ``std``,
420 8. The struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` fields
421 ``category`` and ``group`` did not catch on and/or were not
422 implemented as expected and therefore removed.
424 9. The :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl was added to
425 negotiate data formats as with
426 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`, but without the overhead of
427 programming the hardware and regardless of I/O in progress.
429 In struct v4l2_format the ``fmt`` union was
430 extended to contain struct v4l2_window. All
431 image format negotiations are now possible with ``VIDIOC_G_FMT``,
432 ``VIDIOC_S_FMT`` and ``VIDIOC_TRY_FMT``; ioctl. The ``VIDIOC_G_WIN``
433 and ``VIDIOC_S_WIN`` ioctls to prepare for a video overlay were
434 removed. The ``type`` field changed to type enum v4l2_buf_type and
435 the buffer type names changed as follows.
445 * - ``V4L2_BUF_TYPE_CAPTURE``
446 - ``V4L2_BUF_TYPE_VIDEO_CAPTURE``
447 * - ``V4L2_BUF_TYPE_CODECIN``
449 * - ``V4L2_BUF_TYPE_CODECOUT``
451 * - ``V4L2_BUF_TYPE_EFFECTSIN``
453 * - ``V4L2_BUF_TYPE_EFFECTSIN2``
455 * - ``V4L2_BUF_TYPE_EFFECTSOUT``
457 * - ``V4L2_BUF_TYPE_VIDEOOUT``
458 - ``V4L2_BUF_TYPE_VIDEO_OUTPUT``
460 - ``V4L2_BUF_TYPE_VIDEO_OVERLAY``
462 - ``V4L2_BUF_TYPE_VBI_CAPTURE``
464 - ``V4L2_BUF_TYPE_VBI_OUTPUT``
466 - ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE``
468 - ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``
469 * - ``V4L2_BUF_TYPE_PRIVATE_BASE``
470 - ``V4L2_BUF_TYPE_PRIVATE`` (but this is deprecated)
472 10. In struct v4l2_fmtdesc a enum v4l2_buf_type field named ``type`` was
473 added as in struct v4l2_format. The ``VIDIOC_ENUM_FBUFFMT`` ioctl is no
474 longer needed and was removed. These calls can be replaced by
475 :ref:`VIDIOC_ENUM_FMT` with type ``V4L2_BUF_TYPE_VIDEO_OVERLAY``.
477 11. In struct v4l2_pix_format the ``depth``
478 field was removed, assuming applications which recognize the format
479 by its four-character-code already know the color depth, and others
480 do not care about it. The same rationale lead to the removal of the
481 ``V4L2_FMT_FLAG_COMPRESSED`` flag. The
482 ``V4L2_FMT_FLAG_SWCONVECOMPRESSED`` flag was removed because drivers
483 are not supposed to convert images in kernel space. A user library
484 of conversion functions should be provided instead. The
485 ``V4L2_FMT_FLAG_BYTESPERLINE`` flag was redundant. Applications can
486 set the ``bytesperline`` field to zero to get a reasonable default.
487 Since the remaining flags were replaced as well, the ``flags`` field
490 The interlace flags were replaced by a enum v4l2_field value in a
491 newly added ``field`` field.
499 * - ``V4L2_FMT_FLAG_NOT_INTERLACED``
501 * - ``V4L2_FMT_FLAG_INTERLACED`` = ``V4L2_FMT_FLAG_COMBINED``
502 - ``V4L2_FIELD_INTERLACED``
503 * - ``V4L2_FMT_FLAG_TOPFIELD`` = ``V4L2_FMT_FLAG_ODDFIELD``
505 * - ``V4L2_FMT_FLAG_BOTFIELD`` = ``V4L2_FMT_FLAG_EVENFIELD``
506 - ``V4L2_FIELD_BOTTOM``
508 - ``V4L2_FIELD_SEQ_TB``
510 - ``V4L2_FIELD_SEQ_BT``
512 - ``V4L2_FIELD_ALTERNATE``
514 The color space flags were replaced by a enum v4l2_colorspace value in
515 a newly added ``colorspace`` field, where one of
516 ``V4L2_COLORSPACE_SMPTE170M``, ``V4L2_COLORSPACE_BT878``,
517 ``V4L2_COLORSPACE_470_SYSTEM_M`` or
518 ``V4L2_COLORSPACE_470_SYSTEM_BG`` replaces ``V4L2_FMT_CS_601YUV``.
520 12. In struct v4l2_requestbuffers the
521 ``type`` field was properly defined as enum v4l2_buf_type. Buffer types
522 changed as mentioned above. A new ``memory`` field of type
523 enum v4l2_memory was added to distinguish between
524 I/O methods using buffers allocated by the driver or the
525 application. See :ref:`io` for details.
527 13. In struct v4l2_buffer the ``type`` field was
528 properly defined as enum v4l2_buf_type.
529 Buffer types changed as mentioned above. A ``field`` field of type
530 enum v4l2_field was added to indicate if a
531 buffer contains a top or bottom field. The old field flags were
532 removed. Since no unadjusted system time clock was added to the
533 kernel as planned, the ``timestamp`` field changed back from type
534 stamp_t, an unsigned 64 bit integer expressing the sample time in
535 nanoseconds, to struct timeval. With the addition
536 of a second memory mapping method the ``offset`` field moved into
537 union ``m``, and a new ``memory`` field of type enum v4l2_memory
538 was added to distinguish between
539 I/O methods. See :ref:`io` for details.
541 The ``V4L2_BUF_REQ_CONTIG`` flag was used by the V4L compatibility
542 layer, after changes to this code it was no longer needed. The
543 ``V4L2_BUF_ATTR_DEVICEMEM`` flag would indicate if the buffer was
544 indeed allocated in device memory rather than DMA-able system
545 memory. It was barely useful and so was removed.
547 14. In struct v4l2_framebuffer the
548 ``base[3]`` array anticipating double- and triple-buffering in
549 off-screen video memory, however without defining a synchronization
550 mechanism, was replaced by a single pointer. The
551 ``V4L2_FBUF_CAP_SCALEUP`` and ``V4L2_FBUF_CAP_SCALEDOWN`` flags were
552 removed. Applications can determine this capability more accurately
553 using the new cropping and scaling interface. The
554 ``V4L2_FBUF_CAP_CLIPPING`` flag was replaced by
555 ``V4L2_FBUF_CAP_LIST_CLIPPING`` and
556 ``V4L2_FBUF_CAP_BITMAP_CLIPPING``.
558 15. In struct v4l2_clip the ``x``, ``y``,
559 ``width`` and ``height`` field moved into a ``c`` substructure of
560 type struct v4l2_rect. The ``x`` and ``y``
561 fields were renamed to ``left`` and ``top``, i. e. offsets to a
562 context dependent origin.
564 16. In struct v4l2_window the ``x``, ``y``,
565 ``width`` and ``height`` field moved into a ``w`` substructure as
566 above. A ``field`` field of type enum v4l2_field was added to
567 distinguish between field and frame (interlaced) overlay.
569 17. The digital zoom interface, including struct ``v4l2_zoomcap``,
570 struct ``v4l2_zoom``, ``V4L2_ZOOM_NONCAP`` and
571 ``V4L2_ZOOM_WHILESTREAMING`` was replaced by a new cropping and
572 scaling interface. The previously unused
573 struct v4l2_cropcap and struct v4l2_crop
574 where redefined for this purpose. See :ref:`crop` for details.
576 18. In struct v4l2_vbi_format the
577 ``SAMPLE_FORMAT`` field now contains a four-character-code as used
578 to identify video image formats and ``V4L2_PIX_FMT_GREY`` replaces
579 the ``V4L2_VBI_SF_UBYTE`` define. The ``reserved`` field was
582 19. In struct v4l2_captureparm the type of
583 the ``timeperframe`` field changed from unsigned long to
584 struct v4l2_fract. This allows the accurate
585 expression of multiples of the NTSC-M frame rate 30000 / 1001. A new
586 field ``readbuffers`` was added to control the driver behaviour in
589 Similar changes were made to struct v4l2_outputparm.
591 20. The struct ``v4l2_performance`` and
592 ``VIDIOC_G_PERF`` ioctl were dropped. Except when using the
593 :ref:`read/write I/O method <rw>`, which is limited anyway, this
594 information is already available to applications.
596 21. The example transformation from RGB to YCbCr color space in the old
597 V4L2 documentation was inaccurate, this has been corrected in
604 1. A new capability flag ``V4L2_CAP_RADIO`` was added for radio devices.
605 Prior to this change radio devices would identify solely by having
606 exactly one tuner whose type field reads ``V4L2_TUNER_RADIO``.
608 2. An optional driver access priority mechanism was added, see
609 :ref:`app-pri` for details.
611 3. The audio input and output interface was found to be incomplete.
613 Previously the :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl would
614 enumerate the available audio inputs. An ioctl to determine the
615 current audio input, if more than one combines with the current video
616 input, did not exist. So ``VIDIOC_G_AUDIO`` was renamed to
617 ``VIDIOC_G_AUDIO_OLD``, this ioctl was removed on Kernel 2.6.39. The
618 :ref:`VIDIOC_ENUMAUDIO` ioctl was added to
619 enumerate audio inputs, while
620 :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` now reports the current
623 The same changes were made to
624 :ref:`VIDIOC_G_AUDOUT <VIDIOC_G_AUDOUT>` and
625 :ref:`VIDIOC_ENUMAUDOUT <VIDIOC_ENUMAUDOUT>`.
627 Until further the "videodev" module will automatically translate
628 between the old and new ioctls, but drivers and applications must be
629 updated to successfully compile again.
631 4. The :ref:`VIDIOC_OVERLAY` ioctl was incorrectly
632 defined with write-read parameter. It was changed to write-only,
633 while the write-read version was renamed to ``VIDIOC_OVERLAY_OLD``.
634 The old ioctl was removed on Kernel 2.6.39. Until further the
635 "videodev" kernel module will automatically translate to the new
636 version, so drivers must be recompiled, but not applications.
638 5. :ref:`overlay` incorrectly stated that clipping rectangles define
639 regions where the video can be seen. Correct is that clipping
640 rectangles define regions where *no* video shall be displayed and so
641 the graphics surface can be seen.
643 6. The :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` and
644 :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls were defined with
645 write-only parameter, inconsistent with other ioctls modifying their
646 argument. They were changed to write-read, while a ``_OLD`` suffix
647 was added to the write-only versions. The old ioctls were removed on
648 Kernel 2.6.39. Drivers and applications assuming a constant parameter
655 1. In :ref:`pixfmt-rgb` the following pixel formats were incorrectly
656 transferred from Bill Dirks' V4L2 specification. Descriptions below
657 refer to bytes in memory, in ascending address order.
666 - In this document prior to revision 0.5
668 * - ``V4L2_PIX_FMT_RGB24``
671 * - ``V4L2_PIX_FMT_BGR24``
674 * - ``V4L2_PIX_FMT_RGB32``
677 * - ``V4L2_PIX_FMT_BGR32``
682 The ``V4L2_PIX_FMT_BGR24`` example was always correct.
684 In :ref:`v4l-image-properties` the mapping of the V4L
685 ``VIDEO_PALETTE_RGB24`` and ``VIDEO_PALETTE_RGB32`` formats to V4L2
686 pixel formats was accordingly corrected.
688 2. Unrelated to the fixes above, drivers may still interpret some V4L2
689 RGB pixel formats differently. These issues have yet to be addressed,
690 for details see :ref:`pixfmt-rgb`.
693 V4L2 in Linux 2.6.6, 2004-05-09
694 ===============================
696 1. The :ref:`VIDIOC_CROPCAP` ioctl was incorrectly
697 defined with read-only parameter. It is now defined as write-read
698 ioctl, while the read-only version was renamed to
699 ``VIDIOC_CROPCAP_OLD``. The old ioctl was removed on Kernel 2.6.39.
705 1. A new field ``input`` (former ``reserved[0]``) was added to the
706 struct v4l2_buffer. Purpose of this
707 field is to alternate between video inputs (e. g. cameras) in step
708 with the video capturing process. This function must be enabled with
709 the new ``V4L2_BUF_FLAG_INPUT`` flag. The ``flags`` field is no
713 V4L2 spec erratum 2004-08-01
714 ============================
716 1. The return value of the :ref:`func-open` function was incorrectly
719 2. Audio output ioctls end in -AUDOUT, not -AUDIOOUT.
721 3. In the Current Audio Input example the ``VIDIOC_G_AUDIO`` ioctl took
724 4. The documentation of the :ref:`VIDIOC_QBUF` and
725 :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctls did not mention the
726 struct v4l2_buffer ``memory`` field. It was
727 also missing from examples. Also on the ``VIDIOC_DQBUF`` page the ``EIO``
728 error code was not documented.
734 1. A new sliced VBI interface was added. It is documented in
735 :ref:`sliced` and replaces the interface first proposed in V4L2
742 1. The :ref:`VIDIOC_LOG_STATUS` ioctl was added.
744 2. New video standards ``V4L2_STD_NTSC_443``, ``V4L2_STD_SECAM_LC``,
745 ``V4L2_STD_SECAM_DK`` (a set of SECAM D, K and K1), and
746 ``V4L2_STD_ATSC`` (a set of ``V4L2_STD_ATSC_8_VSB`` and
747 ``V4L2_STD_ATSC_16_VSB``) were defined. Note the ``V4L2_STD_525_60``
748 set now includes ``V4L2_STD_NTSC_443``. See also
751 3. The ``VIDIOC_G_COMP`` and ``VIDIOC_S_COMP`` ioctl were renamed to
752 ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` respectively. Their
753 argument was replaced by a struct
754 ``v4l2_mpeg_compression`` pointer. (The
755 ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls where removed
759 V4L2 spec erratum 2005-11-27
760 ============================
762 The capture example in :ref:`capture-example` called the
763 :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctl without checking if
764 cropping is supported. In the video standard selection example in
765 :ref:`standard` the :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` call used
766 the wrong argument type.
769 V4L2 spec erratum 2006-01-10
770 ============================
772 1. The ``V4L2_IN_ST_COLOR_KILL`` flag in struct v4l2_input not only
773 indicates if the color killer is enabled, but also if it is active.
774 (The color killer disables color decoding when it detects no color
775 in the video signal to improve the image quality.)
777 2. :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` is a write-read ioctl, not
778 write-only as stated on its reference page. The ioctl changed in 2003
782 V4L2 spec erratum 2006-02-03
783 ============================
785 1. In struct v4l2_captureparm and struct v4l2_outputparm the ``timeperframe``
786 field gives the time in seconds, not microseconds.
789 V4L2 spec erratum 2006-02-04
790 ============================
792 1. The ``clips`` field in struct v4l2_window
793 must point to an array of struct v4l2_clip, not
794 a linked list, because drivers ignore the
795 struct v4l2_clip. ``next`` pointer.
800 1. New video standard macros were added: ``V4L2_STD_NTSC_M_KR`` (NTSC M
801 South Korea), and the sets ``V4L2_STD_MN``, ``V4L2_STD_B``,
802 ``V4L2_STD_GH`` and ``V4L2_STD_DK``. The ``V4L2_STD_NTSC`` and
803 ``V4L2_STD_SECAM`` sets now include ``V4L2_STD_NTSC_M_KR`` and
804 ``V4L2_STD_SECAM_LC`` respectively.
806 2. A new ``V4L2_TUNER_MODE_LANG1_LANG2`` was defined to record both
807 languages of a bilingual program. The use of
808 ``V4L2_TUNER_MODE_STEREO`` for this purpose is deprecated now. See
809 the :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` section for details.
812 V4L2 spec erratum 2006-09-23 (Draft 0.15)
813 =========================================
815 1. In various places ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` and
816 ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT`` of the sliced VBI interface were
817 not mentioned along with other buffer types.
819 2. In :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` it was clarified that the
820 struct v4l2_audio ``mode`` field is a flags field.
822 3. :ref:`VIDIOC_QUERYCAP` did not mention the sliced VBI and radio
825 4. In :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` it was clarified that
826 applications must initialize the tuner ``type`` field of
827 struct v4l2_frequency before calling
828 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>`.
830 5. The ``reserved`` array in struct v4l2_requestbuffers has 2 elements,
833 6. In :ref:`output` and :ref:`raw-vbi` the device file names
834 ``/dev/vout`` which never caught on were replaced by ``/dev/video``.
836 7. With Linux 2.6.15 the possible range for VBI device minor numbers was
837 extended from 224-239 to 224-255. Accordingly device file names
838 ``/dev/vbi0`` to ``/dev/vbi31`` are possible now.
844 1. New ioctls :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
845 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
846 :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` were added, a
847 flag to skip unsupported controls with
848 :ref:`VIDIOC_QUERYCTRL`, new control types
849 ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_TYPE_CTRL_CLASS``
850 (enum v4l2_ctrl_type), and new control flags
851 ``V4L2_CTRL_FLAG_READ_ONLY``, ``V4L2_CTRL_FLAG_UPDATE``,
852 ``V4L2_CTRL_FLAG_INACTIVE`` and ``V4L2_CTRL_FLAG_SLIDER``
853 (:ref:`control-flags`). See :ref:`extended-controls` for details.
859 1. In struct v4l2_sliced_vbi_cap a
860 buffer type field was added replacing a reserved field. Note on
861 architectures where the size of enum types differs from int types the
862 size of the structure changed. The
863 :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl
864 was redefined from being read-only to write-read. Applications must
865 initialize the type field and clear the reserved fields now. These
866 changes may *break the compatibility* with older drivers and
869 2. The ioctls :ref:`VIDIOC_ENUM_FRAMESIZES`
871 :ref:`VIDIOC_ENUM_FRAMEINTERVALS`
874 3. A new pixel format ``V4L2_PIX_FMT_RGB444`` (:ref:`pixfmt-rgb`) was
878 V4L2 spec erratum 2006-10-12 (Draft 0.17)
879 =========================================
881 1. ``V4L2_PIX_FMT_HM12`` (:ref:`reserved-formats`) is a YUV 4:2:0, not
888 1. The ``videodev2.h`` header file is now dual licensed under GNU
889 General Public License version two or later, and under a 3-clause
896 1. Two new field orders ``V4L2_FIELD_INTERLACED_TB`` and
897 ``V4L2_FIELD_INTERLACED_BT`` were added. See enum v4l2_field for
900 2. Three new clipping/blending methods with a global or straight or
901 inverted local alpha value were added to the video overlay interface.
902 See the description of the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`
903 and :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` ioctls for details.
905 A new ``global_alpha`` field was added to struct v4l2_window,
906 extending the structure. This may **break compatibility** with
907 applications using a struct v4l2_window directly. However the
908 :ref:`VIDIOC_G/S/TRY_FMT <VIDIOC_G_FMT>` ioctls, which take a
909 pointer to a struct v4l2_format parent structure
910 with padding bytes at the end, are not affected.
912 3. The format of the ``chromakey`` field in struct v4l2_window changed from
913 "host order RGB32" to a pixel value in the same format as the framebuffer.
914 This may **break compatibility** with existing applications. Drivers
915 supporting the "host order RGB32" format are not known.
921 1. The pixel formats ``V4L2_PIX_FMT_PAL8``, ``V4L2_PIX_FMT_YUV444``,
922 ``V4L2_PIX_FMT_YUV555``, ``V4L2_PIX_FMT_YUV565`` and
923 ``V4L2_PIX_FMT_YUV32`` were added.
929 1. The pixel formats :ref:`V4L2_PIX_FMT_Y16 <V4L2-PIX-FMT-Y16>` and
930 :ref:`V4L2_PIX_FMT_SBGGR16 <V4L2-PIX-FMT-SBGGR16>` were added.
932 2. New :ref:`controls <control>` ``V4L2_CID_POWER_LINE_FREQUENCY``,
933 ``V4L2_CID_HUE_AUTO``, ``V4L2_CID_WHITE_BALANCE_TEMPERATURE``,
934 ``V4L2_CID_SHARPNESS`` and ``V4L2_CID_BACKLIGHT_COMPENSATION`` were
935 added. The controls ``V4L2_CID_BLACK_LEVEL``, ``V4L2_CID_WHITENESS``,
936 ``V4L2_CID_HCENTER`` and ``V4L2_CID_VCENTER`` were deprecated.
938 3. A :ref:`Camera controls class <camera-controls>` was added, with
939 the new controls ``V4L2_CID_EXPOSURE_AUTO``,
940 ``V4L2_CID_EXPOSURE_ABSOLUTE``, ``V4L2_CID_EXPOSURE_AUTO_PRIORITY``,
941 ``V4L2_CID_PAN_RELATIVE``, ``V4L2_CID_TILT_RELATIVE``,
942 ``V4L2_CID_PAN_RESET``, ``V4L2_CID_TILT_RESET``,
943 ``V4L2_CID_PAN_ABSOLUTE``, ``V4L2_CID_TILT_ABSOLUTE``,
944 ``V4L2_CID_FOCUS_ABSOLUTE``, ``V4L2_CID_FOCUS_RELATIVE`` and
945 ``V4L2_CID_FOCUS_AUTO``.
947 4. The ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls, which
948 were superseded by the :ref:`extended controls <extended-controls>`
949 interface in Linux 2.6.18, where finally removed from the
950 ``videodev2.h`` header file.
956 1. The pixel formats ``V4L2_PIX_FMT_Y16`` and ``V4L2_PIX_FMT_SBGGR16``
959 2. Added user controls ``V4L2_CID_CHROMA_AGC`` and
960 ``V4L2_CID_COLOR_KILLER``.
966 1. The :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
967 and the ``V4L2_CAP_HW_FREQ_SEEK`` capability were added.
969 2. The pixel formats ``V4L2_PIX_FMT_YVYU``, ``V4L2_PIX_FMT_PCA501``,
970 ``V4L2_PIX_FMT_PCA505``, ``V4L2_PIX_FMT_PCA508``,
971 ``V4L2_PIX_FMT_PCA561``, ``V4L2_PIX_FMT_SGBRG8``,
972 ``V4L2_PIX_FMT_PAC207`` and ``V4L2_PIX_FMT_PJPG`` were added.
978 1. Added ``V4L2_MPEG_AUDIO_ENCODING_AAC`` and
979 ``V4L2_MPEG_AUDIO_ENCODING_AC3`` MPEG audio encodings.
981 2. Added ``V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC`` MPEG video encoding.
983 3. The pixel formats ``V4L2_PIX_FMT_SGRBG10`` and
984 ``V4L2_PIX_FMT_SGRBG10DPCM8`` were added.
990 1. The ``VIDIOC_G_CHIP_IDENT`` ioctl was renamed to
991 ``VIDIOC_G_CHIP_IDENT_OLD`` and ``VIDIOC_DBG_G_CHIP_IDENT`` was
992 introduced in its place. The old struct ``v4l2_chip_ident`` was renamed to
993 struct ``v4l2_chip_ident_old``.
995 2. The pixel formats ``V4L2_PIX_FMT_VYUY``, ``V4L2_PIX_FMT_NV16`` and
996 ``V4L2_PIX_FMT_NV61`` were added.
998 3. Added camera controls ``V4L2_CID_ZOOM_ABSOLUTE``,
999 ``V4L2_CID_ZOOM_RELATIVE``, ``V4L2_CID_ZOOM_CONTINUOUS`` and
1000 ``V4L2_CID_PRIVACY``.
1003 V4L2 in Linux 2.6.30
1004 ====================
1006 1. New control flag ``V4L2_CTRL_FLAG_WRITE_ONLY`` was added.
1008 2. New control ``V4L2_CID_COLORFX`` was added.
1011 V4L2 in Linux 2.6.32
1012 ====================
1014 1. In order to be easier to compare a V4L2 API and a kernel version, now
1015 V4L2 API is numbered using the Linux Kernel version numeration.
1017 2. Finalized the RDS capture API. See :ref:`rds` for more information.
1019 3. Added new capabilities for modulators and RDS encoders.
1021 4. Add description for libv4l API.
1023 5. Added support for string controls via new type
1024 ``V4L2_CTRL_TYPE_STRING``.
1026 6. Added ``V4L2_CID_BAND_STOP_FILTER`` documentation.
1028 7. Added FM Modulator (FM TX) Extended Control Class:
1029 ``V4L2_CTRL_CLASS_FM_TX`` and their Control IDs.
1031 8. Added FM Receiver (FM RX) Extended Control Class:
1032 ``V4L2_CTRL_CLASS_FM_RX`` and their Control IDs.
1034 9. Added Remote Controller chapter, describing the default Remote
1035 Controller mapping for media devices.
1038 V4L2 in Linux 2.6.33
1039 ====================
1041 1. Added support for Digital Video timings in order to support HDTV
1042 receivers and transmitters.
1045 V4L2 in Linux 2.6.34
1046 ====================
1048 1. Added ``V4L2_CID_IRIS_ABSOLUTE`` and ``V4L2_CID_IRIS_RELATIVE``
1049 controls to the :ref:`Camera controls class <camera-controls>`.
1052 V4L2 in Linux 2.6.37
1053 ====================
1055 1. Remove the vtx (videotext/teletext) API. This API was no longer used
1056 and no hardware exists to verify the API. Nor were any userspace
1057 applications found that used it. It was originally scheduled for
1061 V4L2 in Linux 2.6.39
1062 ====================
1064 1. The old VIDIOC_*_OLD symbols and V4L1 support were removed.
1066 2. Multi-planar API added. Does not affect the compatibility of current
1067 drivers and applications. See :ref:`multi-planar API <planar-apis>`
1074 1. VIDIOC_QUERYCAP now returns a per-subsystem version instead of a
1077 Standardize an error code for invalid ioctl.
1079 Added V4L2_CTRL_TYPE_BITMASK.
1085 1. V4L2_CTRL_FLAG_VOLATILE was added to signal volatile controls to
1088 2. Add selection API for extended control over cropping and composing.
1089 Does not affect the compatibility of current drivers and
1090 applications. See :ref:`selection API <selection-api>` for details.
1096 1. Added ``V4L2_CID_ALPHA_COMPONENT`` control to the
1097 :ref:`User controls class <control>`.
1099 2. Added the device_caps field to struct v4l2_capabilities and added
1100 the new V4L2_CAP_DEVICE_CAPS capability.
1106 1. Added :ref:`JPEG compression control class <jpeg-controls>`.
1108 2. Extended the DV Timings API:
1109 :ref:`VIDIOC_ENUM_DV_TIMINGS`,
1110 :ref:`VIDIOC_QUERY_DV_TIMINGS` and
1111 :ref:`VIDIOC_DV_TIMINGS_CAP`.
1117 1. Added integer menus, the new type will be
1118 V4L2_CTRL_TYPE_INTEGER_MENU.
1120 2. Added selection API for V4L2 subdev interface:
1121 :ref:`VIDIOC_SUBDEV_G_SELECTION` and
1122 :ref:`VIDIOC_SUBDEV_S_SELECTION <VIDIOC_SUBDEV_G_SELECTION>`.
1124 3. Added ``V4L2_COLORFX_ANTIQUE``, ``V4L2_COLORFX_ART_FREEZE``,
1125 ``V4L2_COLORFX_AQUA``, ``V4L2_COLORFX_SILHOUETTE``,
1126 ``V4L2_COLORFX_SOLARIZATION``, ``V4L2_COLORFX_VIVID`` and
1127 ``V4L2_COLORFX_ARBITRARY_CBCR`` menu items to the
1128 ``V4L2_CID_COLORFX`` control.
1130 4. Added ``V4L2_CID_COLORFX_CBCR`` control.
1132 5. Added camera controls ``V4L2_CID_AUTO_EXPOSURE_BIAS``,
1133 ``V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE``,
1134 ``V4L2_CID_IMAGE_STABILIZATION``, ``V4L2_CID_ISO_SENSITIVITY``,
1135 ``V4L2_CID_ISO_SENSITIVITY_AUTO``, ``V4L2_CID_EXPOSURE_METERING``,
1136 ``V4L2_CID_SCENE_MODE``, ``V4L2_CID_3A_LOCK``,
1137 ``V4L2_CID_AUTO_FOCUS_START``, ``V4L2_CID_AUTO_FOCUS_STOP``,
1138 ``V4L2_CID_AUTO_FOCUS_STATUS`` and ``V4L2_CID_AUTO_FOCUS_RANGE``.
1144 1. Replaced ``input`` in struct v4l2_buffer by
1145 ``reserved2`` and removed ``V4L2_BUF_FLAG_INPUT``.
1147 2. Added V4L2_CAP_VIDEO_M2M and V4L2_CAP_VIDEO_M2M_MPLANE
1150 3. Added support for frequency band enumerations:
1151 :ref:`VIDIOC_ENUM_FREQ_BANDS`.
1157 1. Added timestamp types to ``flags`` field in
1158 struct v4l2_buffer. See :ref:`buffer-flags`.
1160 2. Added ``V4L2_EVENT_CTRL_CH_RANGE`` control event changes flag. See
1161 :ref:`ctrl-changes-flags`.
1167 1. Removed obsolete and unused DV_PRESET ioctls VIDIOC_G_DV_PRESET,
1168 VIDIOC_S_DV_PRESET, VIDIOC_QUERY_DV_PRESET and
1169 VIDIOC_ENUM_DV_PRESET. Remove the related v4l2_input/output
1170 capability flags V4L2_IN_CAP_PRESETS and V4L2_OUT_CAP_PRESETS.
1172 2. Added new debugging ioctl
1173 :ref:`VIDIOC_DBG_G_CHIP_INFO`.
1179 1. Remove obsolete ``VIDIOC_DBG_G_CHIP_IDENT`` ioctl.
1185 1. In struct v4l2_rect, the type of ``width`` and
1186 ``height`` fields changed from _s32 to _u32.
1192 1. Added Software Defined Radio (SDR) Interface.
1198 1. Added event V4L2_EVENT_SOURCE_CHANGE.
1204 1. Extended struct v4l2_pix_format. Added
1207 2. Added compound control types and
1208 :ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>`.
1214 1. Added ``V4L2_CID_PAN_SPEED`` and ``V4L2_CID_TILT_SPEED`` camera
1221 1. Rewrote Colorspace chapter, added new enum v4l2_ycbcr_encoding
1222 and enum v4l2_quantization fields to struct v4l2_pix_format,
1223 struct v4l2_pix_format_mplane and struct v4l2_mbus_framefmt.
1228 1. Renamed ``V4L2_TUNER_ADC`` to ``V4L2_TUNER_SDR``. The use of
1229 ``V4L2_TUNER_ADC`` is deprecated now.
1231 2. Added ``V4L2_CID_RF_TUNER_RF_GAIN`` RF Tuner control.
1233 3. Added transmitter support for Software Defined Radio (SDR) Interface.
1238 Relation of V4L2 to other Linux multimedia APIs
1239 ===============================================
1247 The X Video Extension (abbreviated XVideo or just Xv) is an extension of
1248 the X Window system, implemented for example by the XFree86 project. Its
1249 scope is similar to V4L2, an API to video capture and output devices for
1250 X clients. Xv allows applications to display live video in a window,
1251 send window contents to a TV output, and capture or output still images
1252 in XPixmaps [#f1]_. With their implementation XFree86 makes the extension
1253 available across many operating systems and architectures.
1255 Because the driver is embedded into the X server Xv has a number of
1256 advantages over the V4L2 :ref:`video overlay interface <overlay>`. The
1257 driver can easily determine the overlay target, i. e. visible graphics
1258 memory or off-screen buffers for a destructive overlay. It can program
1259 the RAMDAC for a non-destructive overlay, scaling or color-keying, or
1260 the clipping functions of the video capture hardware, always in sync
1261 with drawing operations or windows moving or changing their stacking
1264 To combine the advantages of Xv and V4L a special Xv driver exists in
1265 XFree86 and XOrg, just programming any overlay capable Video4Linux
1266 device it finds. To enable it ``/etc/X11/XF86Config`` must contain these
1275 As of XFree86 4.2 this driver still supports only V4L ioctls, however it
1276 should work just fine with all V4L2 devices through the V4L2
1277 backward-compatibility layer. Since V4L2 permits multiple opens it is
1278 possible (if supported by the V4L2 driver) to capture video while an X
1279 client requested video overlay. Restrictions of simultaneous capturing
1280 and overlay are discussed in :ref:`overlay` apply.
1282 Only marginally related to V4L2, XFree86 extended Xv to support hardware
1283 YUV to RGB conversion and scaling for faster video playback, and added
1284 an interface to MPEG-2 decoding hardware. This API is useful to display
1285 images captured with V4L2 devices.
1291 V4L2 does not support digital terrestrial, cable or satellite broadcast.
1292 A separate project aiming at digital receivers exists. You can find its
1293 homepage at `https://linuxtv.org <https://linuxtv.org>`__. The Linux
1294 DVB API has no connection to the V4L2 API except that drivers for hybrid
1295 hardware may support both.
1306 Experimental API Elements
1307 =========================
1309 The following V4L2 API elements are currently experimental and may
1310 change in the future.
1312 - :ref:`VIDIOC_DBG_G_REGISTER` and
1313 :ref:`VIDIOC_DBG_S_REGISTER <VIDIOC_DBG_G_REGISTER>` ioctls.
1315 - :ref:`VIDIOC_DBG_G_CHIP_INFO` ioctl.
1320 Obsolete API Elements
1321 =====================
1323 The following V4L2 API elements were superseded by new interfaces and
1324 should not be implemented in new drivers.
1326 - ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls. Use Extended
1327 Controls, :ref:`extended-controls`.
1329 - VIDIOC_G_DV_PRESET, VIDIOC_S_DV_PRESET,
1330 VIDIOC_ENUM_DV_PRESETS and VIDIOC_QUERY_DV_PRESET ioctls. Use
1331 the DV Timings API (:ref:`dv-timings`).
1333 - ``VIDIOC_SUBDEV_G_CROP`` and ``VIDIOC_SUBDEV_S_CROP`` ioctls. Use
1334 ``VIDIOC_SUBDEV_G_SELECTION`` and ``VIDIOC_SUBDEV_S_SELECTION``,
1335 :ref:`VIDIOC_SUBDEV_G_SELECTION`.
1338 This is not implemented in XFree86.
projects / linux-2.6-microblaze.git / blob