1 .. -*- coding: utf-8; mode: rst -*-
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 :c:func:`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 struct
40 :c:type:`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 :ref:`v4l2_capability <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
120 :ref:`v4l2_clip <v4l2-clip>` was changed for compatibility with
123 2. ``V4L2_TUNER_SUB_LANG1`` was added. (1999-09-05)
125 3. All ioctl() commands that used an integer argument now take a pointer
126 to an integer. Where it makes sense, ioctls will return the actual
127 new value in the integer pointed to by the argument, a common
128 convention in the V4L2 API. The affected ioctls are: VIDIOC_PREVIEW,
129 VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ,
130 VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example
135 err = ioctl (fd, VIDIOC_XXX, V4L2_XXX);
142 int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a);
144 4. All the different get- and set-format commands were swept into one
145 :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
146 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl taking a union and a
147 type field selecting the union member as parameter. Purpose is to
148 simplify the API by eliminating several ioctls and to allow new and
149 driver private data streams without adding new ioctls.
151 This change obsoletes the following ioctls: ``VIDIOC_S_INFMT``,
152 ``VIDIOC_G_INFMT``, ``VIDIOC_S_OUTFMT``, ``VIDIOC_G_OUTFMT``,
153 ``VIDIOC_S_VBIFMT`` and ``VIDIOC_G_VBIFMT``. The image format
154 structure :c:type:`struct v4l2_format` was renamed to struct
155 :ref:`v4l2_pix_format <v4l2-pix-format>`, while struct
156 :ref:`v4l2_format <v4l2-format>` is now the envelopping structure
157 for all format negotiations.
159 5. Similar to the changes above, the ``VIDIOC_G_PARM`` and
160 ``VIDIOC_S_PARM`` ioctls were merged with ``VIDIOC_G_OUTPARM`` and
161 ``VIDIOC_S_OUTPARM``. A ``type`` field in the new struct
162 :ref:`v4l2_streamparm <v4l2-streamparm>` selects the respective
165 This change obsoletes the ``VIDIOC_G_OUTPARM`` and
166 ``VIDIOC_S_OUTPARM`` ioctls.
168 6. Control enumeration was simplified, and two new control flags were
169 introduced and one dropped. The ``catname`` field was replaced by a
172 Drivers can now flag unsupported and temporarily unavailable controls
173 with ``V4L2_CTRL_FLAG_DISABLED`` and ``V4L2_CTRL_FLAG_GRABBED``
174 respectively. The ``group`` name indicates a possibly narrower
175 classification than the ``category``. In other words, there may be
176 multiple groups within a category. Controls within a group would
177 typically be drawn within a group box. Controls in different
178 categories might have a greater separation, or may even appear in
181 7. The struct :ref:`v4l2_buffer <v4l2-buffer>` ``timestamp`` was
182 changed to a 64 bit integer, containing the sampling or output time
183 of the frame in nanoseconds. Additionally timestamps will be in
184 absolute system time, not starting from zero at the beginning of a
185 stream. The data type name for timestamps is stamp_t, defined as a
186 signed 64-bit integer. Output devices should not send a buffer out
187 until the time in the timestamp field has arrived. I would like to
188 follow SGI's lead, and adopt a multimedia timestamping system like
189 their UST (Unadjusted System Time). See
190 http://web.archive.org/web/\*/http://reality.sgi.com
191 /cpirazzi_engr/lg/time/intro.html. UST uses timestamps that are
192 64-bit signed integers (not struct timeval's) and given in nanosecond
193 units. The UST clock starts at zero when the system is booted and
194 runs continuously and uniformly. It takes a little over 292 years for
195 UST to overflow. There is no way to set the UST clock. The regular
196 Linux time-of-day clock can be changed periodically, which would
197 cause errors if it were being used for timestamping a multimedia
198 stream. A real UST style clock will require some support in the
199 kernel that is not there yet. But in anticipation, I will change the
200 timestamp field to a 64-bit integer, and I will change the
201 v4l2_masterclock_gettime() function (used only by drivers) to
202 return a 64-bit integer.
204 8. A ``sequence`` field was added to struct
205 :ref:`v4l2_buffer <v4l2-buffer>`. The ``sequence`` field counts
206 captured frames, it is ignored by output devices. When a capture
207 driver drops a frame, the sequence number of that frame is skipped.
210 V4L2 Version 0.20 incremental changes
211 =====================================
213 1999-12-23: In struct :ref:`v4l2_vbi_format <v4l2-vbi-format>` the
214 ``reserved1`` field became ``offset``. Previously drivers were required
215 to clear the ``reserved1`` field.
217 2000-01-13: The ``V4L2_FMT_FLAG_NOT_INTERLACED`` flag was added.
219 2000-07-31: The ``linux/poll.h`` header is now included by
220 ``videodev.h`` for compatibility with the original ``videodev.h`` file.
222 2000-11-20: ``V4L2_TYPE_VBI_OUTPUT`` and ``V4L2_PIX_FMT_Y41P`` were
225 2000-11-25: ``V4L2_TYPE_VBI_INPUT`` was added.
227 2000-12-04: A couple typos in symbol names were fixed.
229 2001-01-18: To avoid namespace conflicts the ``fourcc`` macro defined in
230 the ``videodev.h`` header file was renamed to ``v4l2_fourcc``.
232 2001-01-25: A possible driver-level compatibility problem between the
233 ``videodev.h`` file in Linux 2.4.0 and the ``videodev.h`` file included
234 in the ``videodevX`` patch was fixed. Users of an earlier version of
235 ``videodevX`` on Linux 2.4.0 should recompile their V4L and V4L2
238 2001-01-26: A possible kernel-level incompatibility between the
239 ``videodev.h`` file in the ``videodevX`` patch and the ``videodev.h``
240 file in Linux 2.2.x with devfs patches applied was fixed.
242 2001-03-02: Certain V4L ioctls which pass data in both direction
243 although they are defined with read-only parameter, did not work
244 correctly through the backward compatibility layer. [Solution?]
246 2001-04-13: Big endian 16-bit RGB formats were added.
248 2001-09-17: New YUV formats and the
249 :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
250 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctls were added.
251 (The old ``VIDIOC_G_FREQ`` and ``VIDIOC_S_FREQ`` ioctls did not take
252 multiple tuners into account.)
254 2000-09-18: ``V4L2_BUF_TYPE_VBI`` was added. This may *break
255 compatibility* as the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
256 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls may fail now if the struct
257 :c:type:`struct v4l2_fmt` ``type`` field does not contain
258 ``V4L2_BUF_TYPE_VBI``. In the documentation of the struct
259 :ref:`v4l2_vbi_format <v4l2-vbi-format>` ``offset`` field the
260 ambiguous phrase "rising edge" was changed to "leading edge".
263 V4L2 Version 0.20 2000-11-23
264 ============================
266 A number of changes were made to the raw VBI interface.
268 1. Figures clarifying the line numbering scheme were added to the V4L2
269 API specification. The ``start``\ [0] and ``start``\ [1] fields no
270 longer count line numbers beginning at zero. Rationale: a) The
271 previous definition was unclear. b) The ``start``\ [] values are
272 ordinal numbers. c) There is no point in inventing a new line
273 numbering scheme. We now use line number as defined by ITU-R, period.
274 Compatibility: Add one to the start values. Applications depending on
275 the previous semantics may not function correctly.
277 2. The restriction "count[0] > 0 and count[1] > 0" has been relaxed to
278 "(count[0] + count[1]) > 0". Rationale: Drivers may allocate
279 resources at scan line granularity and some data services are
280 transmitted only on the first field. The comment that both ``count``
281 values will usually be equal is misleading and pointless and has been
282 removed. This change *breaks compatibility* with earlier versions:
283 Drivers may return ``EINVAL``, applications may not function correctly.
285 3. Drivers are again permitted to return negative (unknown) start values
286 as proposed earlier. Why this feature was dropped is unclear. This
287 change may *break compatibility* with applications depending on the
288 start values being positive. The use of ``EBUSY`` and ``EINVAL``
289 error codes with the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl was
290 clarified. The ``EBUSY`` error code was finally documented, and the
291 ``reserved2`` field which was previously mentioned only in the
292 ``videodev.h`` header file.
294 4. New buffer types ``V4L2_TYPE_VBI_INPUT`` and ``V4L2_TYPE_VBI_OUTPUT``
295 were added. The former is an alias for the old ``V4L2_TYPE_VBI``, the
296 latter was missing in the ``videodev.h`` file.
299 V4L2 Version 0.20 2002-07-25
300 ============================
302 Added sliced VBI interface proposal.
305 V4L2 in Linux 2.5.46, 2002-10
306 =============================
308 Around October-November 2002, prior to an announced feature freeze of
309 Linux 2.5, the API was revised, drawing from experience with V4L2 0.20.
310 This unnamed version was finally merged into Linux 2.5.46.
312 1. As specified in :ref:`related`, drivers must make related device
313 functions available under all minor device numbers.
315 2. The :ref:`open() <func-open>` function requires access mode
316 ``O_RDWR`` regardless of the device type. All V4L2 drivers
317 exchanging data with applications must support the ``O_NONBLOCK``
318 flag. The ``O_NOIO`` flag, a V4L2 symbol which aliased the
319 meaningless ``O_TRUNC`` to indicate accesses without data exchange
320 (panel applications) was dropped. Drivers must stay in "panel mode"
321 until the application attempts to initiate a data exchange, see
324 3. The struct :ref:`v4l2_capability <v4l2-capability>` changed
325 dramatically. Note that also the size of the structure changed,
326 which is encoded in the ioctl request code, thus older V4L2 devices
327 will respond with an ``EINVAL`` error code to the new
328 :ref:`VIDIOC_QUERYCAP` ioctl.
330 There are new fields to identify the driver, a new RDS device
331 function ``V4L2_CAP_RDS_CAPTURE``, the ``V4L2_CAP_AUDIO`` flag
332 indicates if the device has any audio connectors, another I/O
333 capability ``V4L2_CAP_ASYNCIO`` can be flagged. In response to these
334 changes the ``type`` field became a bit set and was merged into the
335 ``flags`` field. ``V4L2_FLAG_TUNER`` was renamed to
336 ``V4L2_CAP_TUNER``, ``V4L2_CAP_VIDEO_OVERLAY`` replaced
337 ``V4L2_FLAG_PREVIEW`` and ``V4L2_CAP_VBI_CAPTURE`` and
338 ``V4L2_CAP_VBI_OUTPUT`` replaced ``V4L2_FLAG_DATA_SERVICE``.
339 ``V4L2_FLAG_READ`` and ``V4L2_FLAG_WRITE`` were merged into
340 ``V4L2_CAP_READWRITE``.
342 The redundant fields ``inputs``, ``outputs`` and ``audios`` were
343 removed. These properties can be determined as described in
344 :ref:`video` and :ref:`audio`.
346 The somewhat volatile and therefore barely useful fields
347 ``maxwidth``, ``maxheight``, ``minwidth``, ``minheight``,
348 ``maxframerate`` were removed. This information is available as
349 described in :ref:`format` and :ref:`standard`.
351 ``V4L2_FLAG_SELECT`` was removed. We believe the select() function
352 is important enough to require support of it in all V4L2 drivers
353 exchanging data with applications. The redundant
354 ``V4L2_FLAG_MONOCHROME`` flag was removed, this information is
355 available as described in :ref:`format`.
357 4. In struct :ref:`v4l2_input <v4l2-input>` the ``assoc_audio``
358 field and the ``capability`` field and its only flag
359 ``V4L2_INPUT_CAP_AUDIO`` was replaced by the new ``audioset`` field.
360 Instead of linking one video input to one audio input this field
361 reports all audio inputs this video input combines with.
363 New fields are ``tuner`` (reversing the former link from tuners to
364 video inputs), ``std`` and ``status``.
366 Accordingly struct :ref:`v4l2_output <v4l2-output>` lost its
367 ``capability`` and ``assoc_audio`` fields. ``audioset``,
368 ``modulator`` and ``std`` where added instead.
370 5. The struct :ref:`v4l2_audio <v4l2-audio>` field ``audio`` was
371 renamed to ``index``, for consistency with other structures. A new
372 capability flag ``V4L2_AUDCAP_STEREO`` was added to indicated if the
373 audio input in question supports stereo sound.
374 ``V4L2_AUDCAP_EFFECTS`` and the corresponding ``V4L2_AUDMODE`` flags
375 where removed. This can be easily implemented using controls.
376 (However the same applies to AVL which is still there.)
378 Again for consistency the struct
379 :ref:`v4l2_audioout <v4l2-audioout>` field ``audio`` was renamed
382 6. The struct :ref:`v4l2_tuner <v4l2-tuner>` ``input`` field was
383 replaced by an ``index`` field, permitting devices with multiple
384 tuners. The link between video inputs and tuners is now reversed,
385 inputs point to their tuner. The ``std`` substructure became a
386 simple set (more about this below) and moved into struct
387 :ref:`v4l2_input <v4l2-input>`. A ``type`` field was added.
389 Accordingly in struct :ref:`v4l2_modulator <v4l2-modulator>` the
390 ``output`` was replaced by an ``index`` field.
392 In struct :ref:`v4l2_frequency <v4l2-frequency>` the ``port``
393 field was replaced by a ``tuner`` field containing the respective
394 tuner or modulator index number. A tuner ``type`` field was added
395 and the ``reserved`` field became larger for future extensions
396 (satellite tuners in particular).
398 7. The idea of completely transparent video standards was dropped.
399 Experience showed that applications must be able to work with video
400 standards beyond presenting the user a menu. Instead of enumerating
401 supported standards with an ioctl applications can now refer to
402 standards by :ref:`v4l2_std_id <v4l2-std-id>` and symbols
403 defined in the ``videodev2.h`` header file. For details see
404 :ref:`standard`. The :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` and
405 :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` now take a pointer to this
406 type as argument. :ref:`VIDIOC_QUERYSTD` was
407 added to autodetect the received standard, if the hardware has this
408 capability. In struct :ref:`v4l2_standard <v4l2-standard>` an
409 ``index`` field was added for
410 :ref:`VIDIOC_ENUMSTD`. A
411 :ref:`v4l2_std_id <v4l2-std-id>` field named ``id`` was added as
412 machine readable identifier, also replacing the ``transmission``
413 field. The misleading ``framerate`` field was renamed to
414 ``frameperiod``. The now obsolete ``colorstandard`` information,
415 originally needed to distguish between variations of standards, were
418 Struct :c:type:`struct v4l2_enumstd` ceased to be.
419 :ref:`VIDIOC_ENUMSTD` now takes a pointer to a
420 struct :ref:`v4l2_standard <v4l2-standard>` directly. The
421 information which standards are supported by a particular video
422 input or output moved into struct :ref:`v4l2_input <v4l2-input>`
423 and struct :ref:`v4l2_output <v4l2-output>` fields named ``std``,
426 8. The struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` fields
427 ``category`` and ``group`` did not catch on and/or were not
428 implemented as expected and therefore removed.
430 9. The :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl was added to
431 negotiate data formats as with
432 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`, but without the overhead of
433 programming the hardware and regardless of I/O in progress.
435 In struct :ref:`v4l2_format <v4l2-format>` the ``fmt`` union was
436 extended to contain struct :ref:`v4l2_window <v4l2-window>`. All
437 image format negotiations are now possible with ``VIDIOC_G_FMT``,
438 ``VIDIOC_S_FMT`` and ``VIDIOC_TRY_FMT``; ioctl. The ``VIDIOC_G_WIN``
439 and ``VIDIOC_S_WIN`` ioctls to prepare for a video overlay were
440 removed. The ``type`` field changed to type enum
441 :ref:`v4l2_buf_type <v4l2-buf-type>` and the buffer type names
455 - enum :ref:`v4l2_buf_type <v4l2-buf-type>`
459 - ``V4L2_BUF_TYPE_CAPTURE``
461 - ``V4L2_BUF_TYPE_VIDEO_CAPTURE``
465 - ``V4L2_BUF_TYPE_CODECIN``
471 - ``V4L2_BUF_TYPE_CODECOUT``
477 - ``V4L2_BUF_TYPE_EFFECTSIN``
483 - ``V4L2_BUF_TYPE_EFFECTSIN2``
489 - ``V4L2_BUF_TYPE_EFFECTSOUT``
495 - ``V4L2_BUF_TYPE_VIDEOOUT``
497 - ``V4L2_BUF_TYPE_VIDEO_OUTPUT``
503 - ``V4L2_BUF_TYPE_VIDEO_OVERLAY``
509 - ``V4L2_BUF_TYPE_VBI_CAPTURE``
515 - ``V4L2_BUF_TYPE_VBI_OUTPUT``
521 - ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE``
527 - ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``
531 - ``V4L2_BUF_TYPE_PRIVATE_BASE``
533 - ``V4L2_BUF_TYPE_PRIVATE`` (but this is deprecated)
536 10. In struct :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` a enum
537 :ref:`v4l2_buf_type <v4l2-buf-type>` field named ``type`` was
538 added as in struct :ref:`v4l2_format <v4l2-format>`. The
539 ``VIDIOC_ENUM_FBUFFMT`` ioctl is no longer needed and was removed.
540 These calls can be replaced by
541 :ref:`VIDIOC_ENUM_FMT` with type
542 ``V4L2_BUF_TYPE_VIDEO_OVERLAY``.
544 11. In struct :ref:`v4l2_pix_format <v4l2-pix-format>` the ``depth``
545 field was removed, assuming applications which recognize the format
546 by its four-character-code already know the color depth, and others
547 do not care about it. The same rationale lead to the removal of the
548 ``V4L2_FMT_FLAG_COMPRESSED`` flag. The
549 ``V4L2_FMT_FLAG_SWCONVECOMPRESSED`` flag was removed because drivers
550 are not supposed to convert images in kernel space. A user library
551 of conversion functions should be provided instead. The
552 ``V4L2_FMT_FLAG_BYTESPERLINE`` flag was redundant. Applications can
553 set the ``bytesperline`` field to zero to get a reasonable default.
554 Since the remaining flags were replaced as well, the ``flags`` field
557 The interlace flags were replaced by a enum
558 :ref:`v4l2_field <v4l2-field>` value in a newly added ``field``
572 - enum :ref:`v4l2_field <v4l2-field>`
576 - ``V4L2_FMT_FLAG_NOT_INTERLACED``
582 - ``V4L2_FMT_FLAG_INTERLACED`` = ``V4L2_FMT_FLAG_COMBINED``
584 - ``V4L2_FIELD_INTERLACED``
588 - ``V4L2_FMT_FLAG_TOPFIELD`` = ``V4L2_FMT_FLAG_ODDFIELD``
594 - ``V4L2_FMT_FLAG_BOTFIELD`` = ``V4L2_FMT_FLAG_EVENFIELD``
596 - ``V4L2_FIELD_BOTTOM``
602 - ``V4L2_FIELD_SEQ_TB``
608 - ``V4L2_FIELD_SEQ_BT``
614 - ``V4L2_FIELD_ALTERNATE``
617 The color space flags were replaced by a enum
618 :ref:`v4l2_colorspace <v4l2-colorspace>` value in a newly added
619 ``colorspace`` field, where one of ``V4L2_COLORSPACE_SMPTE170M``,
620 ``V4L2_COLORSPACE_BT878``, ``V4L2_COLORSPACE_470_SYSTEM_M`` or
621 ``V4L2_COLORSPACE_470_SYSTEM_BG`` replaces ``V4L2_FMT_CS_601YUV``.
623 12. In struct :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` the
624 ``type`` field was properly defined as enum
625 :ref:`v4l2_buf_type <v4l2-buf-type>`. Buffer types changed as
626 mentioned above. A new ``memory`` field of type enum
627 :ref:`v4l2_memory <v4l2-memory>` was added to distinguish between
628 I/O methods using buffers allocated by the driver or the
629 application. See :ref:`io` for details.
631 13. In struct :ref:`v4l2_buffer <v4l2-buffer>` the ``type`` field was
632 properly defined as enum :ref:`v4l2_buf_type <v4l2-buf-type>`.
633 Buffer types changed as mentioned above. A ``field`` field of type
634 enum :ref:`v4l2_field <v4l2-field>` was added to indicate if a
635 buffer contains a top or bottom field. The old field flags were
636 removed. Since no unadjusted system time clock was added to the
637 kernel as planned, the ``timestamp`` field changed back from type
638 stamp_t, an unsigned 64 bit integer expressing the sample time in
639 nanoseconds, to struct :c:type:`struct timeval`. With the addition
640 of a second memory mapping method the ``offset`` field moved into
641 union ``m``, and a new ``memory`` field of type enum
642 :ref:`v4l2_memory <v4l2-memory>` was added to distinguish between
643 I/O methods. See :ref:`io` for details.
645 The ``V4L2_BUF_REQ_CONTIG`` flag was used by the V4L compatibility
646 layer, after changes to this code it was no longer needed. The
647 ``V4L2_BUF_ATTR_DEVICEMEM`` flag would indicate if the buffer was
648 indeed allocated in device memory rather than DMA-able system
649 memory. It was barely useful and so was removed.
651 14. In struct :ref:`v4l2_framebuffer <v4l2-framebuffer>` the
652 ``base[3]`` array anticipating double- and triple-buffering in
653 off-screen video memory, however without defining a synchronization
654 mechanism, was replaced by a single pointer. The
655 ``V4L2_FBUF_CAP_SCALEUP`` and ``V4L2_FBUF_CAP_SCALEDOWN`` flags were
656 removed. Applications can determine this capability more accurately
657 using the new cropping and scaling interface. The
658 ``V4L2_FBUF_CAP_CLIPPING`` flag was replaced by
659 ``V4L2_FBUF_CAP_LIST_CLIPPING`` and
660 ``V4L2_FBUF_CAP_BITMAP_CLIPPING``.
662 15. In struct :ref:`v4l2_clip <v4l2-clip>` the ``x``, ``y``,
663 ``width`` and ``height`` field moved into a ``c`` substructure of
664 type struct :ref:`v4l2_rect <v4l2-rect>`. The ``x`` and ``y``
665 fields were renamed to ``left`` and ``top``, i. e. offsets to a
666 context dependent origin.
668 16. In struct :ref:`v4l2_window <v4l2-window>` the ``x``, ``y``,
669 ``width`` and ``height`` field moved into a ``w`` substructure as
670 above. A ``field`` field of type %v4l2-field; was added to
671 distinguish between field and frame (interlaced) overlay.
673 17. The digital zoom interface, including struct
674 :c:type:`struct v4l2_zoomcap`, struct
675 :c:type:`struct v4l2_zoom`, ``V4L2_ZOOM_NONCAP`` and
676 ``V4L2_ZOOM_WHILESTREAMING`` was replaced by a new cropping and
677 scaling interface. The previously unused struct
678 :c:type:`struct v4l2_cropcap` and :c:type:`struct v4l2_crop`
679 where redefined for this purpose. See :ref:`crop` for details.
681 18. In struct :ref:`v4l2_vbi_format <v4l2-vbi-format>` the
682 ``SAMPLE_FORMAT`` field now contains a four-character-code as used
683 to identify video image formats and ``V4L2_PIX_FMT_GREY`` replaces
684 the ``V4L2_VBI_SF_UBYTE`` define. The ``reserved`` field was
687 19. In struct :ref:`v4l2_captureparm <v4l2-captureparm>` the type of
688 the ``timeperframe`` field changed from unsigned long to struct
689 :ref:`v4l2_fract <v4l2-fract>`. This allows the accurate
690 expression of multiples of the NTSC-M frame rate 30000 / 1001. A new
691 field ``readbuffers`` was added to control the driver behaviour in
694 Similar changes were made to struct
695 :ref:`v4l2_outputparm <v4l2-outputparm>`.
697 20. The struct :c:type:`struct v4l2_performance` and
698 ``VIDIOC_G_PERF`` ioctl were dropped. Except when using the
699 :ref:`read/write I/O method <rw>`, which is limited anyway, this
700 information is already available to applications.
702 21. The example transformation from RGB to YCbCr color space in the old
703 V4L2 documentation was inaccurate, this has been corrected in
710 1. A new capability flag ``V4L2_CAP_RADIO`` was added for radio devices.
711 Prior to this change radio devices would identify solely by having
712 exactly one tuner whose type field reads ``V4L2_TUNER_RADIO``.
714 2. An optional driver access priority mechanism was added, see
715 :ref:`app-pri` for details.
717 3. The audio input and output interface was found to be incomplete.
719 Previously the :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl would
720 enumerate the available audio inputs. An ioctl to determine the
721 current audio input, if more than one combines with the current video
722 input, did not exist. So ``VIDIOC_G_AUDIO`` was renamed to
723 ``VIDIOC_G_AUDIO_OLD``, this ioctl was removed on Kernel 2.6.39. The
724 :ref:`VIDIOC_ENUMAUDIO` ioctl was added to
725 enumerate audio inputs, while
726 :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` now reports the current
729 The same changes were made to
730 :ref:`VIDIOC_G_AUDOUT <VIDIOC_G_AUDOUT>` and
731 :ref:`VIDIOC_ENUMAUDOUT <VIDIOC_ENUMAUDOUT>`.
733 Until further the "videodev" module will automatically translate
734 between the old and new ioctls, but drivers and applications must be
735 updated to successfully compile again.
737 4. The :ref:`VIDIOC_OVERLAY` ioctl was incorrectly
738 defined with write-read parameter. It was changed to write-only,
739 while the write-read version was renamed to ``VIDIOC_OVERLAY_OLD``.
740 The old ioctl was removed on Kernel 2.6.39. Until further the
741 "videodev" kernel module will automatically translate to the new
742 version, so drivers must be recompiled, but not applications.
744 5. :ref:`overlay` incorrectly stated that clipping rectangles define
745 regions where the video can be seen. Correct is that clipping
746 rectangles define regions where *no* video shall be displayed and so
747 the graphics surface can be seen.
749 6. The :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` and
750 :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls were defined with
751 write-only parameter, inconsistent with other ioctls modifying their
752 argument. They were changed to write-read, while a ``_OLD`` suffix
753 was added to the write-only versions. The old ioctls were removed on
754 Kernel 2.6.39. Drivers and applications assuming a constant parameter
761 1. In :ref:`pixfmt-rgb` the following pixel formats were incorrectly
762 transferred from Bill Dirks' V4L2 specification. Descriptions below
763 refer to bytes in memory, in ascending address order.
776 - In this document prior to revision 0.5
782 - ``V4L2_PIX_FMT_RGB24``
790 - ``V4L2_PIX_FMT_BGR24``
798 - ``V4L2_PIX_FMT_RGB32``
806 - ``V4L2_PIX_FMT_BGR32``
813 The ``V4L2_PIX_FMT_BGR24`` example was always correct.
815 In :ref:`v4l-image-properties` the mapping of the V4L
816 ``VIDEO_PALETTE_RGB24`` and ``VIDEO_PALETTE_RGB32`` formats to V4L2
817 pixel formats was accordingly corrected.
819 2. Unrelated to the fixes above, drivers may still interpret some V4L2
820 RGB pixel formats differently. These issues have yet to be addressed,
821 for details see :ref:`pixfmt-rgb`.
824 V4L2 in Linux 2.6.6, 2004-05-09
825 ===============================
827 1. The :ref:`VIDIOC_CROPCAP` ioctl was incorrectly
828 defined with read-only parameter. It is now defined as write-read
829 ioctl, while the read-only version was renamed to
830 ``VIDIOC_CROPCAP_OLD``. The old ioctl was removed on Kernel 2.6.39.
836 1. A new field ``input`` (former ``reserved[0]``) was added to the
837 struct :ref:`v4l2_buffer <v4l2-buffer>` structure. Purpose of this
838 field is to alternate between video inputs (e. g. cameras) in step
839 with the video capturing process. This function must be enabled with
840 the new ``V4L2_BUF_FLAG_INPUT`` flag. The ``flags`` field is no
844 V4L2 spec erratum 2004-08-01
845 ============================
847 1. The return value of the :ref:`func-open` function was incorrectly
850 2. Audio output ioctls end in -AUDOUT, not -AUDIOOUT.
852 3. In the Current Audio Input example the ``VIDIOC_G_AUDIO`` ioctl took
855 4. The documentation of the :ref:`VIDIOC_QBUF` and
856 :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctls did not mention the
857 struct :ref:`v4l2_buffer <v4l2-buffer>` ``memory`` field. It was
858 also missing from examples. Also on the ``VIDIOC_DQBUF`` page the ``EIO``
859 error code was not documented.
865 1. A new sliced VBI interface was added. It is documented in
866 :ref:`sliced` and replaces the interface first proposed in V4L2
873 1. The :ref:`VIDIOC_LOG_STATUS` ioctl was added.
875 2. New video standards ``V4L2_STD_NTSC_443``, ``V4L2_STD_SECAM_LC``,
876 ``V4L2_STD_SECAM_DK`` (a set of SECAM D, K and K1), and
877 ``V4L2_STD_ATSC`` (a set of ``V4L2_STD_ATSC_8_VSB`` and
878 ``V4L2_STD_ATSC_16_VSB``) were defined. Note the ``V4L2_STD_525_60``
879 set now includes ``V4L2_STD_NTSC_443``. See also
882 3. The ``VIDIOC_G_COMP`` and ``VIDIOC_S_COMP`` ioctl were renamed to
883 ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` respectively. Their
884 argument was replaced by a struct
885 :c:type:`struct v4l2_mpeg_compression` pointer. (The
886 ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls where removed
890 V4L2 spec erratum 2005-11-27
891 ============================
893 The capture example in :ref:`capture-example` called the
894 :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctl without checking if
895 cropping is supported. In the video standard selection example in
896 :ref:`standard` the :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` call used
897 the wrong argument type.
900 V4L2 spec erratum 2006-01-10
901 ============================
903 1. The ``V4L2_IN_ST_COLOR_KILL`` flag in struct
904 :ref:`v4l2_input <v4l2-input>` not only indicates if the color
905 killer is enabled, but also if it is active. (The color killer
906 disables color decoding when it detects no color in the video signal
907 to improve the image quality.)
909 2. :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` is a write-read ioctl, not
910 write-only as stated on its reference page. The ioctl changed in 2003
914 V4L2 spec erratum 2006-02-03
915 ============================
917 1. In struct :ref:`v4l2_captureparm <v4l2-captureparm>` and struct
918 :ref:`v4l2_outputparm <v4l2-outputparm>` the ``timeperframe``
919 field gives the time in seconds, not microseconds.
922 V4L2 spec erratum 2006-02-04
923 ============================
925 1. The ``clips`` field in struct :ref:`v4l2_window <v4l2-window>`
926 must point to an array of struct :ref:`v4l2_clip <v4l2-clip>`, not
927 a linked list, because drivers ignore the struct
928 :c:type:`struct v4l2_clip`. ``next`` pointer.
934 1. New video standard macros were added: ``V4L2_STD_NTSC_M_KR`` (NTSC M
935 South Korea), and the sets ``V4L2_STD_MN``, ``V4L2_STD_B``,
936 ``V4L2_STD_GH`` and ``V4L2_STD_DK``. The ``V4L2_STD_NTSC`` and
937 ``V4L2_STD_SECAM`` sets now include ``V4L2_STD_NTSC_M_KR`` and
938 ``V4L2_STD_SECAM_LC`` respectively.
940 2. A new ``V4L2_TUNER_MODE_LANG1_LANG2`` was defined to record both
941 languages of a bilingual program. The use of
942 ``V4L2_TUNER_MODE_STEREO`` for this purpose is deprecated now. See
943 the :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` section for details.
946 V4L2 spec erratum 2006-09-23 (Draft 0.15)
947 =========================================
949 1. In various places ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` and
950 ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT`` of the sliced VBI interface were
951 not mentioned along with other buffer types.
953 2. In :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` it was clarified that the struct
954 :ref:`v4l2_audio <v4l2-audio>` ``mode`` field is a flags field.
956 3. :ref:`VIDIOC_QUERYCAP` did not mention the sliced VBI and radio
959 4. In :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` it was clarified that applications
960 must initialize the tuner ``type`` field of struct
961 :ref:`v4l2_frequency <v4l2-frequency>` before calling
962 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>`.
964 5. The ``reserved`` array in struct
965 :ref:`v4l2_requestbuffers <v4l2-requestbuffers>` has 2 elements,
968 6. In :ref:`output` and :ref:`raw-vbi` the device file names
969 ``/dev/vout`` which never caught on were replaced by ``/dev/video``.
971 7. With Linux 2.6.15 the possible range for VBI device minor numbers was
972 extended from 224-239 to 224-255. Accordingly device file names
973 ``/dev/vbi0`` to ``/dev/vbi31`` are possible now.
979 1. New ioctls :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
980 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
981 :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` were added, a
982 flag to skip unsupported controls with
983 :ref:`VIDIOC_QUERYCTRL`, new control types
984 ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_TYPE_CTRL_CLASS``
985 (:ref:`v4l2-ctrl-type`), and new control flags
986 ``V4L2_CTRL_FLAG_READ_ONLY``, ``V4L2_CTRL_FLAG_UPDATE``,
987 ``V4L2_CTRL_FLAG_INACTIVE`` and ``V4L2_CTRL_FLAG_SLIDER``
988 (:ref:`control-flags`). See :ref:`extended-controls` for details.
994 1. In struct :ref:`v4l2_sliced_vbi_cap <v4l2-sliced-vbi-cap>` a
995 buffer type field was added replacing a reserved field. Note on
996 architectures where the size of enum types differs from int types the
997 size of the structure changed. The
998 :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl
999 was redefined from being read-only to write-read. Applications must
1000 initialize the type field and clear the reserved fields now. These
1001 changes may *break the compatibility* with older drivers and
1004 2. The ioctls :ref:`VIDIOC_ENUM_FRAMESIZES`
1006 :ref:`VIDIOC_ENUM_FRAMEINTERVALS`
1009 3. A new pixel format ``V4L2_PIX_FMT_RGB444`` (:ref:`rgb-formats`) was
1013 V4L2 spec erratum 2006-10-12 (Draft 0.17)
1014 =========================================
1016 1. ``V4L2_PIX_FMT_HM12`` (:ref:`reserved-formats`) is a YUV 4:2:0, not
1020 V4L2 in Linux 2.6.21
1021 ====================
1023 1. The ``videodev2.h`` header file is now dual licensed under GNU
1024 General Public License version two or later, and under a 3-clause
1028 V4L2 in Linux 2.6.22
1029 ====================
1031 1. Two new field orders ``V4L2_FIELD_INTERLACED_TB`` and
1032 ``V4L2_FIELD_INTERLACED_BT`` were added. See :ref:`v4l2-field` for
1035 2. Three new clipping/blending methods with a global or straight or
1036 inverted local alpha value were added to the video overlay interface.
1037 See the description of the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`
1038 and :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` ioctls for details.
1040 A new ``global_alpha`` field was added to
1041 :ref:`v4l2_window <v4l2-window>`, extending the structure. This
1042 may *break compatibility* with applications using a struct
1043 :c:type:`struct v4l2_window` directly. However the
1044 :ref:`VIDIOC_G/S/TRY_FMT <VIDIOC_G_FMT>` ioctls, which take a
1045 pointer to a :ref:`v4l2_format <v4l2-format>` parent structure
1046 with padding bytes at the end, are not affected.
1048 3. The format of the ``chromakey`` field in struct
1049 :ref:`v4l2_window <v4l2-window>` changed from "host order RGB32"
1050 to a pixel value in the same format as the framebuffer. This may
1051 *break compatibility* with existing applications. Drivers supporting
1052 the "host order RGB32" format are not known.
1055 V4L2 in Linux 2.6.24
1056 ====================
1058 1. The pixel formats ``V4L2_PIX_FMT_PAL8``, ``V4L2_PIX_FMT_YUV444``,
1059 ``V4L2_PIX_FMT_YUV555``, ``V4L2_PIX_FMT_YUV565`` and
1060 ``V4L2_PIX_FMT_YUV32`` were added.
1063 V4L2 in Linux 2.6.25
1064 ====================
1066 1. The pixel formats :ref:`V4L2_PIX_FMT_Y16 <V4L2-PIX-FMT-Y16>` and
1067 :ref:`V4L2_PIX_FMT_SBGGR16 <V4L2-PIX-FMT-SBGGR16>` were added.
1069 2. New :ref:`controls <control>` ``V4L2_CID_POWER_LINE_FREQUENCY``,
1070 ``V4L2_CID_HUE_AUTO``, ``V4L2_CID_WHITE_BALANCE_TEMPERATURE``,
1071 ``V4L2_CID_SHARPNESS`` and ``V4L2_CID_BACKLIGHT_COMPENSATION`` were
1072 added. The controls ``V4L2_CID_BLACK_LEVEL``, ``V4L2_CID_WHITENESS``,
1073 ``V4L2_CID_HCENTER`` and ``V4L2_CID_VCENTER`` were deprecated.
1075 3. A :ref:`Camera controls class <camera-controls>` was added, with
1076 the new controls ``V4L2_CID_EXPOSURE_AUTO``,
1077 ``V4L2_CID_EXPOSURE_ABSOLUTE``, ``V4L2_CID_EXPOSURE_AUTO_PRIORITY``,
1078 ``V4L2_CID_PAN_RELATIVE``, ``V4L2_CID_TILT_RELATIVE``,
1079 ``V4L2_CID_PAN_RESET``, ``V4L2_CID_TILT_RESET``,
1080 ``V4L2_CID_PAN_ABSOLUTE``, ``V4L2_CID_TILT_ABSOLUTE``,
1081 ``V4L2_CID_FOCUS_ABSOLUTE``, ``V4L2_CID_FOCUS_RELATIVE`` and
1082 ``V4L2_CID_FOCUS_AUTO``.
1084 4. The ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls, which
1085 were superseded by the :ref:`extended controls <extended-controls>`
1086 interface in Linux 2.6.18, where finally removed from the
1087 ``videodev2.h`` header file.
1090 V4L2 in Linux 2.6.26
1091 ====================
1093 1. The pixel formats ``V4L2_PIX_FMT_Y16`` and ``V4L2_PIX_FMT_SBGGR16``
1096 2. Added user controls ``V4L2_CID_CHROMA_AGC`` and
1097 ``V4L2_CID_COLOR_KILLER``.
1100 V4L2 in Linux 2.6.27
1101 ====================
1103 1. The :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
1104 and the ``V4L2_CAP_HW_FREQ_SEEK`` capability were added.
1106 2. The pixel formats ``V4L2_PIX_FMT_YVYU``, ``V4L2_PIX_FMT_PCA501``,
1107 ``V4L2_PIX_FMT_PCA505``, ``V4L2_PIX_FMT_PCA508``,
1108 ``V4L2_PIX_FMT_PCA561``, ``V4L2_PIX_FMT_SGBRG8``,
1109 ``V4L2_PIX_FMT_PAC207`` and ``V4L2_PIX_FMT_PJPG`` were added.
1112 V4L2 in Linux 2.6.28
1113 ====================
1115 1. Added ``V4L2_MPEG_AUDIO_ENCODING_AAC`` and
1116 ``V4L2_MPEG_AUDIO_ENCODING_AC3`` MPEG audio encodings.
1118 2. Added ``V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC`` MPEG video encoding.
1120 3. The pixel formats ``V4L2_PIX_FMT_SGRBG10`` and
1121 ``V4L2_PIX_FMT_SGRBG10DPCM8`` were added.
1124 V4L2 in Linux 2.6.29
1125 ====================
1127 1. The ``VIDIOC_G_CHIP_IDENT`` ioctl was renamed to
1128 ``VIDIOC_G_CHIP_IDENT_OLD`` and ``VIDIOC_DBG_G_CHIP_IDENT`` was
1129 introduced in its place. The old struct
1130 :c:type:`struct v4l2_chip_ident` was renamed to
1131 :c:type:`struct v4l2_chip_ident_old`.
1133 2. The pixel formats ``V4L2_PIX_FMT_VYUY``, ``V4L2_PIX_FMT_NV16`` and
1134 ``V4L2_PIX_FMT_NV61`` were added.
1136 3. Added camera controls ``V4L2_CID_ZOOM_ABSOLUTE``,
1137 ``V4L2_CID_ZOOM_RELATIVE``, ``V4L2_CID_ZOOM_CONTINUOUS`` and
1138 ``V4L2_CID_PRIVACY``.
1141 V4L2 in Linux 2.6.30
1142 ====================
1144 1. New control flag ``V4L2_CTRL_FLAG_WRITE_ONLY`` was added.
1146 2. New control ``V4L2_CID_COLORFX`` was added.
1149 V4L2 in Linux 2.6.32
1150 ====================
1152 1. In order to be easier to compare a V4L2 API and a kernel version, now
1153 V4L2 API is numbered using the Linux Kernel version numeration.
1155 2. Finalized the RDS capture API. See :ref:`rds` for more information.
1157 3. Added new capabilities for modulators and RDS encoders.
1159 4. Add description for libv4l API.
1161 5. Added support for string controls via new type
1162 ``V4L2_CTRL_TYPE_STRING``.
1164 6. Added ``V4L2_CID_BAND_STOP_FILTER`` documentation.
1166 7. Added FM Modulator (FM TX) Extended Control Class:
1167 ``V4L2_CTRL_CLASS_FM_TX`` and their Control IDs.
1169 8. Added FM Receiver (FM RX) Extended Control Class:
1170 ``V4L2_CTRL_CLASS_FM_RX`` and their Control IDs.
1172 9. Added Remote Controller chapter, describing the default Remote
1173 Controller mapping for media devices.
1176 V4L2 in Linux 2.6.33
1177 ====================
1179 1. Added support for Digital Video timings in order to support HDTV
1180 receivers and transmitters.
1183 V4L2 in Linux 2.6.34
1184 ====================
1186 1. Added ``V4L2_CID_IRIS_ABSOLUTE`` and ``V4L2_CID_IRIS_RELATIVE``
1187 controls to the :ref:`Camera controls class <camera-controls>`.
1190 V4L2 in Linux 2.6.37
1191 ====================
1193 1. Remove the vtx (videotext/teletext) API. This API was no longer used
1194 and no hardware exists to verify the API. Nor were any userspace
1195 applications found that used it. It was originally scheduled for
1199 V4L2 in Linux 2.6.39
1200 ====================
1202 1. The old VIDIOC_*_OLD symbols and V4L1 support were removed.
1204 2. Multi-planar API added. Does not affect the compatibility of current
1205 drivers and applications. See :ref:`multi-planar API <planar-apis>`
1212 1. VIDIOC_QUERYCAP now returns a per-subsystem version instead of a
1215 Standardize an error code for invalid ioctl.
1217 Added V4L2_CTRL_TYPE_BITMASK.
1223 1. V4L2_CTRL_FLAG_VOLATILE was added to signal volatile controls to
1226 2. Add selection API for extended control over cropping and composing.
1227 Does not affect the compatibility of current drivers and
1228 applications. See :ref:`selection API <selection-api>` for details.
1234 1. Added ``V4L2_CID_ALPHA_COMPONENT`` control to the
1235 :ref:`User controls class <control>`.
1237 2. Added the device_caps field to struct v4l2_capabilities and added
1238 the new V4L2_CAP_DEVICE_CAPS capability.
1244 1. Added :ref:`JPEG compression control class <jpeg-controls>`.
1246 2. Extended the DV Timings API:
1247 :ref:`VIDIOC_ENUM_DV_TIMINGS`,
1248 :ref:`VIDIOC_QUERY_DV_TIMINGS` and
1249 :ref:`VIDIOC_DV_TIMINGS_CAP`.
1255 1. Added integer menus, the new type will be
1256 V4L2_CTRL_TYPE_INTEGER_MENU.
1258 2. Added selection API for V4L2 subdev interface:
1259 :ref:`VIDIOC_SUBDEV_G_SELECTION` and
1260 :ref:`VIDIOC_SUBDEV_S_SELECTION <VIDIOC_SUBDEV_G_SELECTION>`.
1262 3. Added ``V4L2_COLORFX_ANTIQUE``, ``V4L2_COLORFX_ART_FREEZE``,
1263 ``V4L2_COLORFX_AQUA``, ``V4L2_COLORFX_SILHOUETTE``,
1264 ``V4L2_COLORFX_SOLARIZATION``, ``V4L2_COLORFX_VIVID`` and
1265 ``V4L2_COLORFX_ARBITRARY_CBCR`` menu items to the
1266 ``V4L2_CID_COLORFX`` control.
1268 4. Added ``V4L2_CID_COLORFX_CBCR`` control.
1270 5. Added camera controls ``V4L2_CID_AUTO_EXPOSURE_BIAS``,
1271 ``V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE``,
1272 ``V4L2_CID_IMAGE_STABILIZATION``, ``V4L2_CID_ISO_SENSITIVITY``,
1273 ``V4L2_CID_ISO_SENSITIVITY_AUTO``, ``V4L2_CID_EXPOSURE_METERING``,
1274 ``V4L2_CID_SCENE_MODE``, ``V4L2_CID_3A_LOCK``,
1275 ``V4L2_CID_AUTO_FOCUS_START``, ``V4L2_CID_AUTO_FOCUS_STOP``,
1276 ``V4L2_CID_AUTO_FOCUS_STATUS`` and ``V4L2_CID_AUTO_FOCUS_RANGE``.
1282 1. Replaced ``input`` in :c:type:`struct v4l2_buffer` by
1283 ``reserved2`` and removed ``V4L2_BUF_FLAG_INPUT``.
1285 2. Added V4L2_CAP_VIDEO_M2M and V4L2_CAP_VIDEO_M2M_MPLANE
1288 3. Added support for frequency band enumerations:
1289 :ref:`VIDIOC_ENUM_FREQ_BANDS`.
1295 1. Added timestamp types to ``flags`` field in
1296 :c:type:`struct v4l2_buffer`. See :ref:`buffer-flags`.
1298 2. Added ``V4L2_EVENT_CTRL_CH_RANGE`` control event changes flag. See
1299 :ref:`ctrl-changes-flags`.
1305 1. Removed obsolete and unused DV_PRESET ioctls VIDIOC_G_DV_PRESET,
1306 VIDIOC_S_DV_PRESET, VIDIOC_QUERY_DV_PRESET and
1307 VIDIOC_ENUM_DV_PRESET. Remove the related v4l2_input/output
1308 capability flags V4L2_IN_CAP_PRESETS and V4L2_OUT_CAP_PRESETS.
1310 2. Added new debugging ioctl
1311 :ref:`VIDIOC_DBG_G_CHIP_INFO`.
1317 1. Remove obsolete ``VIDIOC_DBG_G_CHIP_IDENT`` ioctl.
1323 1. In struct :c:type:`struct v4l2_rect`, the type of ``width`` and
1324 ``height`` fields changed from _s32 to _u32.
1330 1. Added Software Defined Radio (SDR) Interface.
1336 1. Added event V4L2_EVENT_SOURCE_CHANGE.
1342 1. Extended struct :ref:`v4l2_pix_format <v4l2-pix-format>`. Added
1345 2. Added compound control types and
1346 :ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>`.
1352 1. Added ``V4L2_CID_PAN_SPEED`` and ``V4L2_CID_TILT_SPEED`` camera
1359 1. Rewrote Colorspace chapter, added new enum
1360 :ref:`v4l2_ycbcr_encoding <v4l2-ycbcr-encoding>` and enum
1361 :ref:`v4l2_quantization <v4l2-quantization>` fields to struct
1362 :ref:`v4l2_pix_format <v4l2-pix-format>`, struct
1363 :ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>` and
1364 struct :ref:`v4l2_mbus_framefmt <v4l2-mbus-framefmt>`.
1370 1. Renamed ``V4L2_TUNER_ADC`` to ``V4L2_TUNER_SDR``. The use of
1371 ``V4L2_TUNER_ADC`` is deprecated now.
1373 2. Added ``V4L2_CID_RF_TUNER_RF_GAIN`` RF Tuner control.
1375 3. Added transmitter support for Software Defined Radio (SDR) Interface.
1380 Relation of V4L2 to other Linux multimedia APIs
1381 ===============================================
1389 The X Video Extension (abbreviated XVideo or just Xv) is an extension of
1390 the X Window system, implemented for example by the XFree86 project. Its
1391 scope is similar to V4L2, an API to video capture and output devices for
1392 X clients. Xv allows applications to display live video in a window,
1393 send window contents to a TV output, and capture or output still images
1394 in XPixmaps [#f1]_. With their implementation XFree86 makes the extension
1395 available across many operating systems and architectures.
1397 Because the driver is embedded into the X server Xv has a number of
1398 advantages over the V4L2 :ref:`video overlay interface <overlay>`. The
1399 driver can easily determine the overlay target, i. e. visible graphics
1400 memory or off-screen buffers for a destructive overlay. It can program
1401 the RAMDAC for a non-destructive overlay, scaling or color-keying, or
1402 the clipping functions of the video capture hardware, always in sync
1403 with drawing operations or windows moving or changing their stacking
1406 To combine the advantages of Xv and V4L a special Xv driver exists in
1407 XFree86 and XOrg, just programming any overlay capable Video4Linux
1408 device it finds. To enable it ``/etc/X11/XF86Config`` must contain these
1417 As of XFree86 4.2 this driver still supports only V4L ioctls, however it
1418 should work just fine with all V4L2 devices through the V4L2
1419 backward-compatibility layer. Since V4L2 permits multiple opens it is
1420 possible (if supported by the V4L2 driver) to capture video while an X
1421 client requested video overlay. Restrictions of simultaneous capturing
1422 and overlay are discussed in :ref:`overlay` apply.
1424 Only marginally related to V4L2, XFree86 extended Xv to support hardware
1425 YUV to RGB conversion and scaling for faster video playback, and added
1426 an interface to MPEG-2 decoding hardware. This API is useful to display
1427 images captured with V4L2 devices.
1433 V4L2 does not support digital terrestrial, cable or satellite broadcast.
1434 A separate project aiming at digital receivers exists. You can find its
1435 homepage at `https://linuxtv.org <https://linuxtv.org>`__. The Linux
1436 DVB API has no connection to the V4L2 API except that drivers for hybrid
1437 hardware may support both.
1448 Experimental API Elements
1449 =========================
1451 The following V4L2 API elements are currently experimental and may
1452 change in the future.
1454 - :ref:`VIDIOC_DBG_G_REGISTER` and
1455 :ref:`VIDIOC_DBG_S_REGISTER <VIDIOC_DBG_G_REGISTER>` ioctls.
1457 - :ref:`VIDIOC_DBG_G_CHIP_INFO` ioctl.
1462 Obsolete API Elements
1463 =====================
1465 The following V4L2 API elements were superseded by new interfaces and
1466 should not be implemented in new drivers.
1468 - ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls. Use Extended
1469 Controls, :ref:`extended-controls`.
1471 - VIDIOC_G_DV_PRESET, VIDIOC_S_DV_PRESET,
1472 VIDIOC_ENUM_DV_PRESETS and VIDIOC_QUERY_DV_PRESET ioctls. Use
1473 the DV Timings API (:ref:`dv-timings`).
1475 - ``VIDIOC_SUBDEV_G_CROP`` and ``VIDIOC_SUBDEV_S_CROP`` ioctls. Use
1476 ``VIDIOC_SUBDEV_G_SELECTION`` and ``VIDIOC_SUBDEV_S_SELECTION``,
1477 :ref:`VIDIOC_SUBDEV_G_SELECTION`.
1480 This is not implemented in XFree86.
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