1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
6 ***********************
7 Changes of the V4L2 API
8 ***********************
10 Soon after the V4L API was added to the kernel it was criticised as too
11 inflexible. In August 1998 Bill Dirks proposed a number of improvements
12 and began to work on documentation, example drivers and applications.
13 With the help of other volunteers this eventually became the V4L2 API,
14 not just an extension but a replacement for the V4L API. However it took
15 another four years and two stable kernel releases until the new API was
16 finally accepted for inclusion into the kernel in its present form.
21 1998-08-20: First version.
23 1998-08-27: The :c: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`` :c: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.
68 V4L2 Version 0.16 1999-01-31
69 ============================
71 1999-01-27: There is now one QBUF ioctl, VIDIOC_QWBUF and VIDIOC_QRBUF
72 are gone. VIDIOC_QBUF takes a v4l2_buffer as a parameter. Added
73 digital zoom (cropping) controls.
75 V4L2 Version 0.18 1999-03-16
76 ============================
78 Added a v4l to V4L2 ioctl compatibility layer to videodev.c. Driver
79 writers, this changes how you implement your ioctl handler. See the
80 Driver Writer's Guide. Added some more control id codes.
82 V4L2 Version 0.19 1999-06-05
83 ============================
85 1999-03-18: Fill in the category and catname fields of v4l2_queryctrl
86 objects before passing them to the driver. Required a minor change to
87 the VIDIOC_QUERYCTRL handlers in the sample drivers.
89 1999-03-31: Better compatibility for v4l memory capture ioctls. Requires
90 changes to drivers to fully support new compatibility features, see
91 Driver Writer's Guide and v4l2cap.c. Added new control IDs:
92 V4L2_CID_HFLIP, _VFLIP. Changed V4L2_PIX_FMT_YUV422P to _YUV422P,
93 and _YUV411P to _YUV411P.
95 1999-04-04: Added a few more control IDs.
97 1999-04-07: Added the button control type.
99 1999-05-02: Fixed a typo in videodev.h, and added the
100 V4L2_CTRL_FLAG_GRAYED (later V4L2_CTRL_FLAG_GRABBED) flag.
102 1999-05-20: Definition of VIDIOC_G_CTRL was wrong causing a
103 malfunction of this ioctl.
105 1999-06-05: Changed the value of V4L2_CID_WHITENESS.
107 V4L2 Version 0.20 (1999-09-10)
108 ==============================
110 Version 0.20 introduced a number of changes which were *not backward
111 compatible* with 0.19 and earlier versions. Purpose of these changes was
112 to simplify the API, while making it more extensible and following
113 common Linux driver API conventions.
115 1. Some typos in ``V4L2_FMT_FLAG`` symbols were fixed. struct v4l2_clip
116 was changed for compatibility with v4l. (1999-08-30)
118 2. ``V4L2_TUNER_SUB_LANG1`` was added. (1999-09-05)
120 3. All ioctl() commands that used an integer argument now take a pointer
121 to an integer. Where it makes sense, ioctls will return the actual
122 new value in the integer pointed to by the argument, a common
123 convention in the V4L2 API. The affected ioctls are: VIDIOC_PREVIEW,
124 VIDIOC_STREAMON, VIDIOC_STREAMOFF, VIDIOC_S_FREQ,
125 VIDIOC_S_INPUT, VIDIOC_S_OUTPUT, VIDIOC_S_EFFECT. For example
129 err = ioctl (fd, VIDIOC_XXX, V4L2_XXX);
135 int a = V4L2_XXX; err = ioctl(fd, VIDIOC_XXX, &a);
137 4. All the different get- and set-format commands were swept into one
138 :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
139 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl taking a union and a
140 type field selecting the union member as parameter. Purpose is to
141 simplify the API by eliminating several ioctls and to allow new and
142 driver private data streams without adding new ioctls.
144 This change obsoletes the following ioctls: ``VIDIOC_S_INFMT``,
145 ``VIDIOC_G_INFMT``, ``VIDIOC_S_OUTFMT``, ``VIDIOC_G_OUTFMT``,
146 ``VIDIOC_S_VBIFMT`` and ``VIDIOC_G_VBIFMT``. The image format
147 struct v4l2_format was renamed to struct v4l2_pix_format, while
148 struct v4l2_format is now the envelopping structure
149 for all format negotiations.
151 5. Similar to the changes above, the ``VIDIOC_G_PARM`` and
152 ``VIDIOC_S_PARM`` ioctls were merged with ``VIDIOC_G_OUTPARM`` and
153 ``VIDIOC_S_OUTPARM``. A ``type`` field in the new struct v4l2_streamparm
154 selects the respective union member.
156 This change obsoletes the ``VIDIOC_G_OUTPARM`` and
157 ``VIDIOC_S_OUTPARM`` ioctls.
159 6. Control enumeration was simplified, and two new control flags were
160 introduced and one dropped. The ``catname`` field was replaced by a
163 Drivers can now flag unsupported and temporarily unavailable controls
164 with ``V4L2_CTRL_FLAG_DISABLED`` and ``V4L2_CTRL_FLAG_GRABBED``
165 respectively. The ``group`` name indicates a possibly narrower
166 classification than the ``category``. In other words, there may be
167 multiple groups within a category. Controls within a group would
168 typically be drawn within a group box. Controls in different
169 categories might have a greater separation, or may even appear in
172 7. The struct v4l2_buffer ``timestamp`` was
173 changed to a 64 bit integer, containing the sampling or output time
174 of the frame in nanoseconds. Additionally timestamps will be in
175 absolute system time, not starting from zero at the beginning of a
176 stream. The data type name for timestamps is stamp_t, defined as a
177 signed 64-bit integer. Output devices should not send a buffer out
178 until the time in the timestamp field has arrived. I would like to
179 follow SGI's lead, and adopt a multimedia timestamping system like
180 their UST (Unadjusted System Time). See
181 http://web.archive.org/web/\*/http://reality.sgi.com
182 /cpirazzi_engr/lg/time/intro.html. UST uses timestamps that are
183 64-bit signed integers (not struct timeval's) and given in nanosecond
184 units. The UST clock starts at zero when the system is booted and
185 runs continuously and uniformly. It takes a little over 292 years for
186 UST to overflow. There is no way to set the UST clock. The regular
187 Linux time-of-day clock can be changed periodically, which would
188 cause errors if it were being used for timestamping a multimedia
189 stream. A real UST style clock will require some support in the
190 kernel that is not there yet. But in anticipation, I will change the
191 timestamp field to a 64-bit integer, and I will change the
192 v4l2_masterclock_gettime() function (used only by drivers) to
193 return a 64-bit integer.
195 8. A ``sequence`` field was added to struct v4l2_buffer. The ``sequence``
196 field counts captured frames, it is ignored by output devices. When a
197 capture driver drops a frame, the sequence number of that frame is skipped.
199 V4L2 Version 0.20 incremental changes
200 =====================================
202 1999-12-23: In struct v4l2_vbi_format the
203 ``reserved1`` field became ``offset``. Previously drivers were required
204 to clear the ``reserved1`` field.
206 2000-01-13: The ``V4L2_FMT_FLAG_NOT_INTERLACED`` flag was added.
208 2000-07-31: The ``linux/poll.h`` header is now included by
209 ``videodev.h`` for compatibility with the original ``videodev.h`` file.
211 2000-11-20: ``V4L2_TYPE_VBI_OUTPUT`` and ``V4L2_PIX_FMT_Y41P`` were
214 2000-11-25: ``V4L2_TYPE_VBI_INPUT`` was added.
216 2000-12-04: A couple typos in symbol names were fixed.
218 2001-01-18: To avoid namespace conflicts the ``fourcc`` macro defined in
219 the ``videodev.h`` header file was renamed to ``v4l2_fourcc``.
221 2001-01-25: A possible driver-level compatibility problem between the
222 ``videodev.h`` file in Linux 2.4.0 and the ``videodev.h`` file included
223 in the ``videodevX`` patch was fixed. Users of an earlier version of
224 ``videodevX`` on Linux 2.4.0 should recompile their V4L and V4L2
227 2001-01-26: A possible kernel-level incompatibility between the
228 ``videodev.h`` file in the ``videodevX`` patch and the ``videodev.h``
229 file in Linux 2.2.x with devfs patches applied was fixed.
231 2001-03-02: Certain V4L ioctls which pass data in both direction
232 although they are defined with read-only parameter, did not work
233 correctly through the backward compatibility layer. [Solution?]
235 2001-04-13: Big endian 16-bit RGB formats were added.
237 2001-09-17: New YUV formats and the
238 :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` and
239 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctls were added.
240 (The old ``VIDIOC_G_FREQ`` and ``VIDIOC_S_FREQ`` ioctls did not take
241 multiple tuners into account.)
243 2000-09-18: ``V4L2_BUF_TYPE_VBI`` was added. This may *break
244 compatibility* as the :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and
245 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctls may fail now if the
246 struct ``v4l2_fmt`` ``type`` field does not contain
247 ``V4L2_BUF_TYPE_VBI``. In the documentation of the struct v4l2_vbi_format`,
248 the ``offset`` field the ambiguous phrase "rising edge" was changed to
251 V4L2 Version 0.20 2000-11-23
252 ============================
254 A number of changes were made to the raw VBI interface.
256 1. Figures clarifying the line numbering scheme were added to the V4L2
257 API specification. The ``start``\ [0] and ``start``\ [1] fields no
258 longer count line numbers beginning at zero. Rationale: a) The
259 previous definition was unclear. b) The ``start``\ [] values are
260 ordinal numbers. c) There is no point in inventing a new line
261 numbering scheme. We now use line number as defined by ITU-R, period.
262 Compatibility: Add one to the start values. Applications depending on
263 the previous semantics may not function correctly.
265 2. The restriction "count[0] > 0 and count[1] > 0" has been relaxed to
266 "(count[0] + count[1]) > 0". Rationale: Drivers may allocate
267 resources at scan line granularity and some data services are
268 transmitted only on the first field. The comment that both ``count``
269 values will usually be equal is misleading and pointless and has been
270 removed. This change *breaks compatibility* with earlier versions:
271 Drivers may return ``EINVAL``, applications may not function correctly.
273 3. Drivers are again permitted to return negative (unknown) start values
274 as proposed earlier. Why this feature was dropped is unclear. This
275 change may *break compatibility* with applications depending on the
276 start values being positive. The use of ``EBUSY`` and ``EINVAL``
277 error codes with the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl was
278 clarified. The ``EBUSY`` error code was finally documented, and the
279 ``reserved2`` field which was previously mentioned only in the
280 ``videodev.h`` header file.
282 4. New buffer types ``V4L2_TYPE_VBI_INPUT`` and ``V4L2_TYPE_VBI_OUTPUT``
283 were added. The former is an alias for the old ``V4L2_TYPE_VBI``, the
284 latter was missing in the ``videodev.h`` file.
286 V4L2 Version 0.20 2002-07-25
287 ============================
289 Added sliced VBI interface proposal.
291 V4L2 in Linux 2.5.46, 2002-10
292 =============================
294 Around October-November 2002, prior to an announced feature freeze of
295 Linux 2.5, the API was revised, drawing from experience with V4L2 0.20.
296 This unnamed version was finally merged into Linux 2.5.46.
298 1. As specified in :ref:`related`, drivers must make related device
299 functions available under all minor device numbers.
301 2. The :c:func:`open()` function requires access mode
302 ``O_RDWR`` regardless of the device type. All V4L2 drivers
303 exchanging data with applications must support the ``O_NONBLOCK``
304 flag. The ``O_NOIO`` flag, a V4L2 symbol which aliased the
305 meaningless ``O_TRUNC`` to indicate accesses without data exchange
306 (panel applications) was dropped. Drivers must stay in "panel mode"
307 until the application attempts to initiate a data exchange, see
310 3. The struct v4l2_capability changed
311 dramatically. Note that also the size of the structure changed,
312 which is encoded in the ioctl request code, thus older V4L2 devices
313 will respond with an ``EINVAL`` error code to the new
314 :ref:`VIDIOC_QUERYCAP` ioctl.
316 There are new fields to identify the driver, a new RDS device
317 function ``V4L2_CAP_RDS_CAPTURE``, the ``V4L2_CAP_AUDIO`` flag
318 indicates if the device has any audio connectors, another I/O
319 capability V4L2_CAP_ASYNCIO can be flagged. In response to these
320 changes the ``type`` field became a bit set and was merged into the
321 ``flags`` field. ``V4L2_FLAG_TUNER`` was renamed to
322 ``V4L2_CAP_TUNER``, ``V4L2_CAP_VIDEO_OVERLAY`` replaced
323 ``V4L2_FLAG_PREVIEW`` and ``V4L2_CAP_VBI_CAPTURE`` and
324 ``V4L2_CAP_VBI_OUTPUT`` replaced ``V4L2_FLAG_DATA_SERVICE``.
325 ``V4L2_FLAG_READ`` and ``V4L2_FLAG_WRITE`` were merged into
326 ``V4L2_CAP_READWRITE``.
328 The redundant fields ``inputs``, ``outputs`` and ``audios`` were
329 removed. These properties can be determined as described in
330 :ref:`video` and :ref:`audio`.
332 The somewhat volatile and therefore barely useful fields
333 ``maxwidth``, ``maxheight``, ``minwidth``, ``minheight``,
334 ``maxframerate`` were removed. This information is available as
335 described in :ref:`format` and :ref:`standard`.
337 ``V4L2_FLAG_SELECT`` was removed. We believe the select() function
338 is important enough to require support of it in all V4L2 drivers
339 exchanging data with applications. The redundant
340 ``V4L2_FLAG_MONOCHROME`` flag was removed, this information is
341 available as described in :ref:`format`.
343 4. In struct v4l2_input the ``assoc_audio``
344 field and the ``capability`` field and its only flag
345 ``V4L2_INPUT_CAP_AUDIO`` was replaced by the new ``audioset`` field.
346 Instead of linking one video input to one audio input this field
347 reports all audio inputs this video input combines with.
349 New fields are ``tuner`` (reversing the former link from tuners to
350 video inputs), ``std`` and ``status``.
352 Accordingly struct v4l2_output lost its
353 ``capability`` and ``assoc_audio`` fields. ``audioset``,
354 ``modulator`` and ``std`` where added instead.
356 5. The struct v4l2_audio field ``audio`` was
357 renamed to ``index``, for consistency with other structures. A new
358 capability flag ``V4L2_AUDCAP_STEREO`` was added to indicated if the
359 audio input in question supports stereo sound.
360 ``V4L2_AUDCAP_EFFECTS`` and the corresponding ``V4L2_AUDMODE`` flags
361 where removed. This can be easily implemented using controls.
362 (However the same applies to AVL which is still there.)
364 Again for consistency the struct v4l2_audioout field ``audio`` was renamed
367 6. The struct v4l2_tuner ``input`` field was
368 replaced by an ``index`` field, permitting devices with multiple
369 tuners. The link between video inputs and tuners is now reversed,
370 inputs point to their tuner. The ``std`` substructure became a
371 simple set (more about this below) and moved into struct v4l2_input.
372 A ``type`` field was added.
374 Accordingly in struct v4l2_modulator the
375 ``output`` was replaced by an ``index`` field.
377 In struct v4l2_frequency the ``port``
378 field was replaced by a ``tuner`` field containing the respective
379 tuner or modulator index number. A tuner ``type`` field was added
380 and the ``reserved`` field became larger for future extensions
381 (satellite tuners in particular).
383 7. The idea of completely transparent video standards was dropped.
384 Experience showed that applications must be able to work with video
385 standards beyond presenting the user a menu. Instead of enumerating
386 supported standards with an ioctl applications can now refer to
387 standards by :ref:`v4l2_std_id <v4l2-std-id>` and symbols
388 defined in the ``videodev2.h`` header file. For details see
389 :ref:`standard`. The :ref:`VIDIOC_G_STD <VIDIOC_G_STD>` and
390 :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` now take a pointer to this
391 type as argument. :ref:`VIDIOC_QUERYSTD` was
392 added to autodetect the received standard, if the hardware has this
393 capability. In struct v4l2_standard an
394 ``index`` field was added for
395 :ref:`VIDIOC_ENUMSTD`. A
396 :ref:`v4l2_std_id <v4l2-std-id>` field named ``id`` was added as
397 machine readable identifier, also replacing the ``transmission``
398 field. The misleading ``framerate`` field was renamed to
399 ``frameperiod``. The now obsolete ``colorstandard`` information,
400 originally needed to distguish between variations of standards, were
403 Struct ``v4l2_enumstd`` ceased to be.
404 :ref:`VIDIOC_ENUMSTD` now takes a pointer to a
405 struct v4l2_standard directly. The
406 information which standards are supported by a particular video
407 input or output moved into struct v4l2_input
408 and struct v4l2_output fields named ``std``,
411 8. The struct :ref:`v4l2_queryctrl <v4l2-queryctrl>` fields
412 ``category`` and ``group`` did not catch on and/or were not
413 implemented as expected and therefore removed.
415 9. The :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` ioctl was added to
416 negotiate data formats as with
417 :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`, but without the overhead of
418 programming the hardware and regardless of I/O in progress.
420 In struct v4l2_format the ``fmt`` union was
421 extended to contain struct v4l2_window. All
422 image format negotiations are now possible with ``VIDIOC_G_FMT``,
423 ``VIDIOC_S_FMT`` and ``VIDIOC_TRY_FMT``; ioctl. The ``VIDIOC_G_WIN``
424 and ``VIDIOC_S_WIN`` ioctls to prepare for a video overlay were
425 removed. The ``type`` field changed to type enum v4l2_buf_type and
426 the buffer type names changed as follows.
435 * - ``V4L2_BUF_TYPE_CAPTURE``
436 - ``V4L2_BUF_TYPE_VIDEO_CAPTURE``
437 * - ``V4L2_BUF_TYPE_CODECIN``
439 * - ``V4L2_BUF_TYPE_CODECOUT``
441 * - ``V4L2_BUF_TYPE_EFFECTSIN``
443 * - ``V4L2_BUF_TYPE_EFFECTSIN2``
445 * - ``V4L2_BUF_TYPE_EFFECTSOUT``
447 * - ``V4L2_BUF_TYPE_VIDEOOUT``
448 - ``V4L2_BUF_TYPE_VIDEO_OUTPUT``
450 - ``V4L2_BUF_TYPE_VIDEO_OVERLAY``
452 - ``V4L2_BUF_TYPE_VBI_CAPTURE``
454 - ``V4L2_BUF_TYPE_VBI_OUTPUT``
456 - ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE``
458 - ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT``
459 * - ``V4L2_BUF_TYPE_PRIVATE_BASE``
460 - ``V4L2_BUF_TYPE_PRIVATE`` (but this is deprecated)
462 10. In struct v4l2_fmtdesc a enum v4l2_buf_type field named ``type`` was
463 added as in struct v4l2_format. The ``VIDIOC_ENUM_FBUFFMT`` ioctl is no
464 longer needed and was removed. These calls can be replaced by
465 :ref:`VIDIOC_ENUM_FMT` with type ``V4L2_BUF_TYPE_VIDEO_OVERLAY``.
467 11. In struct v4l2_pix_format the ``depth``
468 field was removed, assuming applications which recognize the format
469 by its four-character-code already know the color depth, and others
470 do not care about it. The same rationale lead to the removal of the
471 ``V4L2_FMT_FLAG_COMPRESSED`` flag. The
472 ``V4L2_FMT_FLAG_SWCONVECOMPRESSED`` flag was removed because drivers
473 are not supposed to convert images in kernel space. A user library
474 of conversion functions should be provided instead. The
475 ``V4L2_FMT_FLAG_BYTESPERLINE`` flag was redundant. Applications can
476 set the ``bytesperline`` field to zero to get a reasonable default.
477 Since the remaining flags were replaced as well, the ``flags`` field
480 The interlace flags were replaced by a enum v4l2_field value in a
481 newly added ``field`` field.
489 * - ``V4L2_FMT_FLAG_NOT_INTERLACED``
491 * - ``V4L2_FMT_FLAG_INTERLACED`` = ``V4L2_FMT_FLAG_COMBINED``
492 - ``V4L2_FIELD_INTERLACED``
493 * - ``V4L2_FMT_FLAG_TOPFIELD`` = ``V4L2_FMT_FLAG_ODDFIELD``
495 * - ``V4L2_FMT_FLAG_BOTFIELD`` = ``V4L2_FMT_FLAG_EVENFIELD``
496 - ``V4L2_FIELD_BOTTOM``
498 - ``V4L2_FIELD_SEQ_TB``
500 - ``V4L2_FIELD_SEQ_BT``
502 - ``V4L2_FIELD_ALTERNATE``
504 The color space flags were replaced by a enum v4l2_colorspace value in
505 a newly added ``colorspace`` field, where one of
506 ``V4L2_COLORSPACE_SMPTE170M``, ``V4L2_COLORSPACE_BT878``,
507 ``V4L2_COLORSPACE_470_SYSTEM_M`` or
508 ``V4L2_COLORSPACE_470_SYSTEM_BG`` replaces ``V4L2_FMT_CS_601YUV``.
510 12. In struct v4l2_requestbuffers the
511 ``type`` field was properly defined as enum v4l2_buf_type. Buffer types
512 changed as mentioned above. A new ``memory`` field of type
513 enum v4l2_memory was added to distinguish between
514 I/O methods using buffers allocated by the driver or the
515 application. See :ref:`io` for details.
517 13. In struct v4l2_buffer the ``type`` field was
518 properly defined as enum v4l2_buf_type.
519 Buffer types changed as mentioned above. A ``field`` field of type
520 enum v4l2_field was added to indicate if a
521 buffer contains a top or bottom field. The old field flags were
522 removed. Since no unadjusted system time clock was added to the
523 kernel as planned, the ``timestamp`` field changed back from type
524 stamp_t, an unsigned 64 bit integer expressing the sample time in
525 nanoseconds, to struct timeval. With the addition
526 of a second memory mapping method the ``offset`` field moved into
527 union ``m``, and a new ``memory`` field of type enum v4l2_memory
528 was added to distinguish between
529 I/O methods. See :ref:`io` for details.
531 The ``V4L2_BUF_REQ_CONTIG`` flag was used by the V4L compatibility
532 layer, after changes to this code it was no longer needed. The
533 ``V4L2_BUF_ATTR_DEVICEMEM`` flag would indicate if the buffer was
534 indeed allocated in device memory rather than DMA-able system
535 memory. It was barely useful and so was removed.
537 14. In struct v4l2_framebuffer the
538 ``base[3]`` array anticipating double- and triple-buffering in
539 off-screen video memory, however without defining a synchronization
540 mechanism, was replaced by a single pointer. The
541 ``V4L2_FBUF_CAP_SCALEUP`` and ``V4L2_FBUF_CAP_SCALEDOWN`` flags were
542 removed. Applications can determine this capability more accurately
543 using the new cropping and scaling interface. The
544 ``V4L2_FBUF_CAP_CLIPPING`` flag was replaced by
545 ``V4L2_FBUF_CAP_LIST_CLIPPING`` and
546 ``V4L2_FBUF_CAP_BITMAP_CLIPPING``.
548 15. In struct v4l2_clip the ``x``, ``y``,
549 ``width`` and ``height`` field moved into a ``c`` substructure of
550 type struct v4l2_rect. The ``x`` and ``y``
551 fields were renamed to ``left`` and ``top``, i. e. offsets to a
552 context dependent origin.
554 16. In struct v4l2_window the ``x``, ``y``,
555 ``width`` and ``height`` field moved into a ``w`` substructure as
556 above. A ``field`` field of type enum v4l2_field was added to
557 distinguish between field and frame (interlaced) overlay.
559 17. The digital zoom interface, including struct ``v4l2_zoomcap``,
560 struct ``v4l2_zoom``, ``V4L2_ZOOM_NONCAP`` and
561 ``V4L2_ZOOM_WHILESTREAMING`` was replaced by a new cropping and
562 scaling interface. The previously unused
563 struct v4l2_cropcap and struct v4l2_crop
564 where redefined for this purpose. See :ref:`crop` for details.
566 18. In struct v4l2_vbi_format the
567 ``SAMPLE_FORMAT`` field now contains a four-character-code as used
568 to identify video image formats and ``V4L2_PIX_FMT_GREY`` replaces
569 the ``V4L2_VBI_SF_UBYTE`` define. The ``reserved`` field was
572 19. In struct v4l2_captureparm the type of
573 the ``timeperframe`` field changed from unsigned long to
574 struct v4l2_fract. This allows the accurate
575 expression of multiples of the NTSC-M frame rate 30000 / 1001. A new
576 field ``readbuffers`` was added to control the driver behaviour in
579 Similar changes were made to struct v4l2_outputparm.
581 20. The struct ``v4l2_performance`` and
582 ``VIDIOC_G_PERF`` ioctl were dropped. Except when using the
583 :ref:`read/write I/O method <rw>`, which is limited anyway, this
584 information is already available to applications.
586 21. The example transformation from RGB to YCbCr color space in the old
587 V4L2 documentation was inaccurate, this has been corrected in
593 1. A new capability flag ``V4L2_CAP_RADIO`` was added for radio devices.
594 Prior to this change radio devices would identify solely by having
595 exactly one tuner whose type field reads ``V4L2_TUNER_RADIO``.
597 2. An optional driver access priority mechanism was added, see
598 :ref:`app-pri` for details.
600 3. The audio input and output interface was found to be incomplete.
602 Previously the :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` ioctl would
603 enumerate the available audio inputs. An ioctl to determine the
604 current audio input, if more than one combines with the current video
605 input, did not exist. So ``VIDIOC_G_AUDIO`` was renamed to
606 ``VIDIOC_G_AUDIO_OLD``, this ioctl was removed on Kernel 2.6.39. The
607 :ref:`VIDIOC_ENUMAUDIO` ioctl was added to
608 enumerate audio inputs, while
609 :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` now reports the current
612 The same changes were made to
613 :ref:`VIDIOC_G_AUDOUT <VIDIOC_G_AUDOUT>` and
614 :ref:`VIDIOC_ENUMAUDOUT <VIDIOC_ENUMAUDOUT>`.
616 Until further the "videodev" module will automatically translate
617 between the old and new ioctls, but drivers and applications must be
618 updated to successfully compile again.
620 4. The :ref:`VIDIOC_OVERLAY` ioctl was incorrectly
621 defined with write-read parameter. It was changed to write-only,
622 while the write-read version was renamed to ``VIDIOC_OVERLAY_OLD``.
623 The old ioctl was removed on Kernel 2.6.39. Until further the
624 "videodev" kernel module will automatically translate to the new
625 version, so drivers must be recompiled, but not applications.
627 5. :ref:`overlay` incorrectly stated that clipping rectangles define
628 regions where the video can be seen. Correct is that clipping
629 rectangles define regions where *no* video shall be displayed and so
630 the graphics surface can be seen.
632 6. The :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` and
633 :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls were defined with
634 write-only parameter, inconsistent with other ioctls modifying their
635 argument. They were changed to write-read, while a ``_OLD`` suffix
636 was added to the write-only versions. The old ioctls were removed on
637 Kernel 2.6.39. Drivers and applications assuming a constant parameter
643 1. In :ref:`pixfmt-rgb` the following pixel formats were incorrectly
644 transferred from Bill Dirks' V4L2 specification. Descriptions below
645 refer to bytes in memory, in ascending address order.
653 - In this document prior to revision 0.5
655 * - ``V4L2_PIX_FMT_RGB24``
658 * - ``V4L2_PIX_FMT_BGR24``
661 * - ``V4L2_PIX_FMT_RGB32``
664 * - ``V4L2_PIX_FMT_BGR32``
668 The ``V4L2_PIX_FMT_BGR24`` example was always correct.
670 In :ref:`v4l-image-properties` the mapping of the V4L
671 ``VIDEO_PALETTE_RGB24`` and ``VIDEO_PALETTE_RGB32`` formats to V4L2
672 pixel formats was accordingly corrected.
674 2. Unrelated to the fixes above, drivers may still interpret some V4L2
675 RGB pixel formats differently. These issues have yet to be addressed,
676 for details see :ref:`pixfmt-rgb`.
678 V4L2 in Linux 2.6.6, 2004-05-09
679 ===============================
681 1. The :ref:`VIDIOC_CROPCAP` ioctl was incorrectly
682 defined with read-only parameter. It is now defined as write-read
683 ioctl, while the read-only version was renamed to
684 ``VIDIOC_CROPCAP_OLD``. The old ioctl was removed on Kernel 2.6.39.
689 1. A new field ``input`` (former ``reserved[0]``) was added to the
690 struct v4l2_buffer. Purpose of this
691 field is to alternate between video inputs (e. g. cameras) in step
692 with the video capturing process. This function must be enabled with
693 the new ``V4L2_BUF_FLAG_INPUT`` flag. The ``flags`` field is no
696 V4L2 spec erratum 2004-08-01
697 ============================
699 1. The return value of the :ref:`func-open` function was incorrectly
702 2. Audio output ioctls end in -AUDOUT, not -AUDIOOUT.
704 3. In the Current Audio Input example the ``VIDIOC_G_AUDIO`` ioctl took
707 4. The documentation of the :ref:`VIDIOC_QBUF` and
708 :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctls did not mention the
709 struct v4l2_buffer ``memory`` field. It was
710 also missing from examples. Also on the ``VIDIOC_DQBUF`` page the ``EIO``
711 error code was not documented.
716 1. A new sliced VBI interface was added. It is documented in
717 :ref:`sliced` and replaces the interface first proposed in V4L2
723 1. The :ref:`VIDIOC_LOG_STATUS` ioctl was added.
725 2. New video standards ``V4L2_STD_NTSC_443``, ``V4L2_STD_SECAM_LC``,
726 ``V4L2_STD_SECAM_DK`` (a set of SECAM D, K and K1), and
727 ``V4L2_STD_ATSC`` (a set of ``V4L2_STD_ATSC_8_VSB`` and
728 ``V4L2_STD_ATSC_16_VSB``) were defined. Note the ``V4L2_STD_525_60``
729 set now includes ``V4L2_STD_NTSC_443``. See also
732 3. The ``VIDIOC_G_COMP`` and ``VIDIOC_S_COMP`` ioctl were renamed to
733 ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` respectively. Their
734 argument was replaced by a struct
735 ``v4l2_mpeg_compression`` pointer. (The
736 ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls where removed
739 V4L2 spec erratum 2005-11-27
740 ============================
742 The capture example in :ref:`capture-example` called the
743 :ref:`VIDIOC_S_CROP <VIDIOC_G_CROP>` ioctl without checking if
744 cropping is supported. In the video standard selection example in
745 :ref:`standard` the :ref:`VIDIOC_S_STD <VIDIOC_G_STD>` call used
746 the wrong argument type.
748 V4L2 spec erratum 2006-01-10
749 ============================
751 1. The ``V4L2_IN_ST_COLOR_KILL`` flag in struct v4l2_input not only
752 indicates if the color killer is enabled, but also if it is active.
753 (The color killer disables color decoding when it detects no color
754 in the video signal to improve the image quality.)
756 2. :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` is a write-read ioctl, not
757 write-only as stated on its reference page. The ioctl changed in 2003
760 V4L2 spec erratum 2006-02-03
761 ============================
763 1. In struct v4l2_captureparm and struct v4l2_outputparm the ``timeperframe``
764 field gives the time in seconds, not microseconds.
766 V4L2 spec erratum 2006-02-04
767 ============================
769 1. The ``clips`` field in struct v4l2_window
770 must point to an array of struct v4l2_clip, not
771 a linked list, because drivers ignore the
772 struct v4l2_clip. ``next`` pointer.
777 1. New video standard macros were added: ``V4L2_STD_NTSC_M_KR`` (NTSC M
778 South Korea), and the sets ``V4L2_STD_MN``, ``V4L2_STD_B``,
779 ``V4L2_STD_GH`` and ``V4L2_STD_DK``. The ``V4L2_STD_NTSC`` and
780 ``V4L2_STD_SECAM`` sets now include ``V4L2_STD_NTSC_M_KR`` and
781 ``V4L2_STD_SECAM_LC`` respectively.
783 2. A new ``V4L2_TUNER_MODE_LANG1_LANG2`` was defined to record both
784 languages of a bilingual program. The use of
785 ``V4L2_TUNER_MODE_STEREO`` for this purpose is deprecated now. See
786 the :ref:`VIDIOC_G_TUNER <VIDIOC_G_TUNER>` section for details.
788 V4L2 spec erratum 2006-09-23 (Draft 0.15)
789 =========================================
791 1. In various places ``V4L2_BUF_TYPE_SLICED_VBI_CAPTURE`` and
792 ``V4L2_BUF_TYPE_SLICED_VBI_OUTPUT`` of the sliced VBI interface were
793 not mentioned along with other buffer types.
795 2. In :ref:`VIDIOC_G_AUDIO <VIDIOC_G_AUDIO>` it was clarified that the
796 struct v4l2_audio ``mode`` field is a flags field.
798 3. :ref:`VIDIOC_QUERYCAP` did not mention the sliced VBI and radio
801 4. In :ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` it was clarified that
802 applications must initialize the tuner ``type`` field of
803 struct v4l2_frequency before calling
804 :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>`.
806 5. The ``reserved`` array in struct v4l2_requestbuffers has 2 elements,
809 6. In :ref:`output` and :ref:`raw-vbi` the device file names
810 ``/dev/vout`` which never caught on were replaced by ``/dev/video``.
812 7. With Linux 2.6.15 the possible range for VBI device minor numbers was
813 extended from 224-239 to 224-255. Accordingly device file names
814 ``/dev/vbi0`` to ``/dev/vbi31`` are possible now.
819 1. New ioctls :ref:`VIDIOC_G_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>`,
820 :ref:`VIDIOC_S_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` and
821 :ref:`VIDIOC_TRY_EXT_CTRLS <VIDIOC_G_EXT_CTRLS>` were added, a
822 flag to skip unsupported controls with
823 :ref:`VIDIOC_QUERYCTRL`, new control types
824 ``V4L2_CTRL_TYPE_INTEGER64`` and ``V4L2_CTRL_TYPE_CTRL_CLASS``
825 (enum v4l2_ctrl_type), and new control flags
826 ``V4L2_CTRL_FLAG_READ_ONLY``, ``V4L2_CTRL_FLAG_UPDATE``,
827 ``V4L2_CTRL_FLAG_INACTIVE`` and ``V4L2_CTRL_FLAG_SLIDER``
828 (:ref:`control-flags`). See :ref:`extended-controls` for details.
833 1. In struct v4l2_sliced_vbi_cap a
834 buffer type field was added replacing a reserved field. Note on
835 architectures where the size of enum types differs from int types the
836 size of the structure changed. The
837 :ref:`VIDIOC_G_SLICED_VBI_CAP <VIDIOC_G_SLICED_VBI_CAP>` ioctl
838 was redefined from being read-only to write-read. Applications must
839 initialize the type field and clear the reserved fields now. These
840 changes may *break the compatibility* with older drivers and
843 2. The ioctls :ref:`VIDIOC_ENUM_FRAMESIZES`
845 :ref:`VIDIOC_ENUM_FRAMEINTERVALS`
848 3. A new pixel format ``V4L2_PIX_FMT_RGB444`` (:ref:`pixfmt-rgb`) was
851 V4L2 spec erratum 2006-10-12 (Draft 0.17)
852 =========================================
854 1. ``V4L2_PIX_FMT_HM12`` (:ref:`reserved-formats`) is a YUV 4:2:0, not
860 1. The ``videodev2.h`` header file is now dual licensed under GNU
861 General Public License version two or later, and under a 3-clause
867 1. Two new field orders ``V4L2_FIELD_INTERLACED_TB`` and
868 ``V4L2_FIELD_INTERLACED_BT`` were added. See enum v4l2_field for
871 2. Three new clipping/blending methods with a global or straight or
872 inverted local alpha value were added to the video overlay interface.
873 See the description of the :ref:`VIDIOC_G_FBUF <VIDIOC_G_FBUF>`
874 and :ref:`VIDIOC_S_FBUF <VIDIOC_G_FBUF>` ioctls for details.
876 A new ``global_alpha`` field was added to struct v4l2_window,
877 extending the structure. This may **break compatibility** with
878 applications using a struct v4l2_window directly. However the
879 :ref:`VIDIOC_G/S/TRY_FMT <VIDIOC_G_FMT>` ioctls, which take a
880 pointer to a struct v4l2_format parent structure
881 with padding bytes at the end, are not affected.
883 3. The format of the ``chromakey`` field in struct v4l2_window changed from
884 "host order RGB32" to a pixel value in the same format as the framebuffer.
885 This may **break compatibility** with existing applications. Drivers
886 supporting the "host order RGB32" format are not known.
891 1. The pixel formats ``V4L2_PIX_FMT_PAL8``, ``V4L2_PIX_FMT_YUV444``,
892 ``V4L2_PIX_FMT_YUV555``, ``V4L2_PIX_FMT_YUV565`` and
893 ``V4L2_PIX_FMT_YUV32`` were added.
898 1. The pixel formats :ref:`V4L2_PIX_FMT_Y16 <V4L2-PIX-FMT-Y16>` and
899 :ref:`V4L2_PIX_FMT_SBGGR16 <V4L2-PIX-FMT-SBGGR16>` were added.
901 2. New :ref:`controls <control>` ``V4L2_CID_POWER_LINE_FREQUENCY``,
902 ``V4L2_CID_HUE_AUTO``, ``V4L2_CID_WHITE_BALANCE_TEMPERATURE``,
903 ``V4L2_CID_SHARPNESS`` and ``V4L2_CID_BACKLIGHT_COMPENSATION`` were
904 added. The controls ``V4L2_CID_BLACK_LEVEL``, ``V4L2_CID_WHITENESS``,
905 ``V4L2_CID_HCENTER`` and ``V4L2_CID_VCENTER`` were deprecated.
907 3. A :ref:`Camera controls class <camera-controls>` was added, with
908 the new controls ``V4L2_CID_EXPOSURE_AUTO``,
909 ``V4L2_CID_EXPOSURE_ABSOLUTE``, ``V4L2_CID_EXPOSURE_AUTO_PRIORITY``,
910 ``V4L2_CID_PAN_RELATIVE``, ``V4L2_CID_TILT_RELATIVE``,
911 ``V4L2_CID_PAN_RESET``, ``V4L2_CID_TILT_RESET``,
912 ``V4L2_CID_PAN_ABSOLUTE``, ``V4L2_CID_TILT_ABSOLUTE``,
913 ``V4L2_CID_FOCUS_ABSOLUTE``, ``V4L2_CID_FOCUS_RELATIVE`` and
914 ``V4L2_CID_FOCUS_AUTO``.
916 4. The ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls, which
917 were superseded by the :ref:`extended controls <extended-controls>`
918 interface in Linux 2.6.18, where finally removed from the
919 ``videodev2.h`` header file.
924 1. The pixel formats ``V4L2_PIX_FMT_Y16`` and ``V4L2_PIX_FMT_SBGGR16``
927 2. Added user controls ``V4L2_CID_CHROMA_AGC`` and
928 ``V4L2_CID_COLOR_KILLER``.
933 1. The :ref:`VIDIOC_S_HW_FREQ_SEEK` ioctl
934 and the ``V4L2_CAP_HW_FREQ_SEEK`` capability were added.
936 2. The pixel formats ``V4L2_PIX_FMT_YVYU``, ``V4L2_PIX_FMT_PCA501``,
937 ``V4L2_PIX_FMT_PCA505``, ``V4L2_PIX_FMT_PCA508``,
938 ``V4L2_PIX_FMT_PCA561``, ``V4L2_PIX_FMT_SGBRG8``,
939 ``V4L2_PIX_FMT_PAC207`` and ``V4L2_PIX_FMT_PJPG`` were added.
944 1. Added ``V4L2_MPEG_AUDIO_ENCODING_AAC`` and
945 ``V4L2_MPEG_AUDIO_ENCODING_AC3`` MPEG audio encodings.
947 2. Added ``V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC`` MPEG video encoding.
949 3. The pixel formats ``V4L2_PIX_FMT_SGRBG10`` and
950 ``V4L2_PIX_FMT_SGRBG10DPCM8`` were added.
955 1. The ``VIDIOC_G_CHIP_IDENT`` ioctl was renamed to
956 ``VIDIOC_G_CHIP_IDENT_OLD`` and ``VIDIOC_DBG_G_CHIP_IDENT`` was
957 introduced in its place. The old struct ``v4l2_chip_ident`` was renamed to
958 struct ``v4l2_chip_ident_old``.
960 2. The pixel formats ``V4L2_PIX_FMT_VYUY``, ``V4L2_PIX_FMT_NV16`` and
961 ``V4L2_PIX_FMT_NV61`` were added.
963 3. Added camera controls ``V4L2_CID_ZOOM_ABSOLUTE``,
964 ``V4L2_CID_ZOOM_RELATIVE``, ``V4L2_CID_ZOOM_CONTINUOUS`` and
965 ``V4L2_CID_PRIVACY``.
970 1. New control flag ``V4L2_CTRL_FLAG_WRITE_ONLY`` was added.
972 2. New control ``V4L2_CID_COLORFX`` was added.
977 1. In order to be easier to compare a V4L2 API and a kernel version, now
978 V4L2 API is numbered using the Linux Kernel version numeration.
980 2. Finalized the RDS capture API. See :ref:`rds` for more information.
982 3. Added new capabilities for modulators and RDS encoders.
984 4. Add description for libv4l API.
986 5. Added support for string controls via new type
987 ``V4L2_CTRL_TYPE_STRING``.
989 6. Added ``V4L2_CID_BAND_STOP_FILTER`` documentation.
991 7. Added FM Modulator (FM TX) Extended Control Class:
992 ``V4L2_CTRL_CLASS_FM_TX`` and their Control IDs.
994 8. Added FM Receiver (FM RX) Extended Control Class:
995 ``V4L2_CTRL_CLASS_FM_RX`` and their Control IDs.
997 9. Added Remote Controller chapter, describing the default Remote
998 Controller mapping for media devices.
1000 V4L2 in Linux 2.6.33
1001 ====================
1003 1. Added support for Digital Video timings in order to support HDTV
1004 receivers and transmitters.
1006 V4L2 in Linux 2.6.34
1007 ====================
1009 1. Added ``V4L2_CID_IRIS_ABSOLUTE`` and ``V4L2_CID_IRIS_RELATIVE``
1010 controls to the :ref:`Camera controls class <camera-controls>`.
1012 V4L2 in Linux 2.6.37
1013 ====================
1015 1. Remove the vtx (videotext/teletext) API. This API was no longer used
1016 and no hardware exists to verify the API. Nor were any userspace
1017 applications found that used it. It was originally scheduled for
1020 V4L2 in Linux 2.6.39
1021 ====================
1023 1. The old VIDIOC_*_OLD symbols and V4L1 support were removed.
1025 2. Multi-planar API added. Does not affect the compatibility of current
1026 drivers and applications. See :ref:`multi-planar API <planar-apis>`
1032 1. VIDIOC_QUERYCAP now returns a per-subsystem version instead of a
1035 Standardize an error code for invalid ioctl.
1037 Added V4L2_CTRL_TYPE_BITMASK.
1042 1. V4L2_CTRL_FLAG_VOLATILE was added to signal volatile controls to
1045 2. Add selection API for extended control over cropping and composing.
1046 Does not affect the compatibility of current drivers and
1047 applications. See :ref:`selection API <selection-api>` for details.
1052 1. Added ``V4L2_CID_ALPHA_COMPONENT`` control to the
1053 :ref:`User controls class <control>`.
1055 2. Added the device_caps field to struct v4l2_capabilities and added
1056 the new V4L2_CAP_DEVICE_CAPS capability.
1061 1. Added :ref:`JPEG compression control class <jpeg-controls>`.
1063 2. Extended the DV Timings API:
1064 :ref:`VIDIOC_ENUM_DV_TIMINGS`,
1065 :ref:`VIDIOC_QUERY_DV_TIMINGS` and
1066 :ref:`VIDIOC_DV_TIMINGS_CAP`.
1071 1. Added integer menus, the new type will be
1072 V4L2_CTRL_TYPE_INTEGER_MENU.
1074 2. Added selection API for V4L2 subdev interface:
1075 :ref:`VIDIOC_SUBDEV_G_SELECTION` and
1076 :ref:`VIDIOC_SUBDEV_S_SELECTION <VIDIOC_SUBDEV_G_SELECTION>`.
1078 3. Added ``V4L2_COLORFX_ANTIQUE``, ``V4L2_COLORFX_ART_FREEZE``,
1079 ``V4L2_COLORFX_AQUA``, ``V4L2_COLORFX_SILHOUETTE``,
1080 ``V4L2_COLORFX_SOLARIZATION``, ``V4L2_COLORFX_VIVID`` and
1081 ``V4L2_COLORFX_ARBITRARY_CBCR`` menu items to the
1082 ``V4L2_CID_COLORFX`` control.
1084 4. Added ``V4L2_CID_COLORFX_CBCR`` control.
1086 5. Added camera controls ``V4L2_CID_AUTO_EXPOSURE_BIAS``,
1087 ``V4L2_CID_AUTO_N_PRESET_WHITE_BALANCE``,
1088 ``V4L2_CID_IMAGE_STABILIZATION``, ``V4L2_CID_ISO_SENSITIVITY``,
1089 ``V4L2_CID_ISO_SENSITIVITY_AUTO``, ``V4L2_CID_EXPOSURE_METERING``,
1090 ``V4L2_CID_SCENE_MODE``, ``V4L2_CID_3A_LOCK``,
1091 ``V4L2_CID_AUTO_FOCUS_START``, ``V4L2_CID_AUTO_FOCUS_STOP``,
1092 ``V4L2_CID_AUTO_FOCUS_STATUS`` and ``V4L2_CID_AUTO_FOCUS_RANGE``.
1097 1. Replaced ``input`` in struct v4l2_buffer by
1098 ``reserved2`` and removed ``V4L2_BUF_FLAG_INPUT``.
1100 2. Added V4L2_CAP_VIDEO_M2M and V4L2_CAP_VIDEO_M2M_MPLANE
1103 3. Added support for frequency band enumerations:
1104 :ref:`VIDIOC_ENUM_FREQ_BANDS`.
1109 1. Added timestamp types to ``flags`` field in
1110 struct v4l2_buffer. See :ref:`buffer-flags`.
1112 2. Added ``V4L2_EVENT_CTRL_CH_RANGE`` control event changes flag. See
1113 :ref:`ctrl-changes-flags`.
1118 1. Removed obsolete and unused DV_PRESET ioctls VIDIOC_G_DV_PRESET,
1119 VIDIOC_S_DV_PRESET, VIDIOC_QUERY_DV_PRESET and
1120 VIDIOC_ENUM_DV_PRESET. Remove the related v4l2_input/output
1121 capability flags V4L2_IN_CAP_PRESETS and V4L2_OUT_CAP_PRESETS.
1123 2. Added new debugging ioctl
1124 :ref:`VIDIOC_DBG_G_CHIP_INFO`.
1129 1. Remove obsolete ``VIDIOC_DBG_G_CHIP_IDENT`` ioctl.
1134 1. In struct v4l2_rect, the type of ``width`` and
1135 ``height`` fields changed from _s32 to _u32.
1140 1. Added Software Defined Radio (SDR) Interface.
1145 1. Added event V4L2_EVENT_SOURCE_CHANGE.
1150 1. Extended struct v4l2_pix_format. Added
1153 2. Added compound control types and
1154 :ref:`VIDIOC_QUERY_EXT_CTRL <VIDIOC_QUERYCTRL>`.
1159 1. Added ``V4L2_CID_PAN_SPEED`` and ``V4L2_CID_TILT_SPEED`` camera
1165 1. Rewrote Colorspace chapter, added new enum v4l2_ycbcr_encoding
1166 and enum v4l2_quantization fields to struct v4l2_pix_format,
1167 struct v4l2_pix_format_mplane and struct v4l2_mbus_framefmt.
1172 1. Renamed ``V4L2_TUNER_ADC`` to ``V4L2_TUNER_SDR``. The use of
1173 ``V4L2_TUNER_ADC`` is deprecated now.
1175 2. Added ``V4L2_CID_RF_TUNER_RF_GAIN`` RF Tuner control.
1177 3. Added transmitter support for Software Defined Radio (SDR) Interface.
1181 Relation of V4L2 to other Linux multimedia APIs
1182 ===============================================
1189 The X Video Extension (abbreviated XVideo or just Xv) is an extension of
1190 the X Window system, implemented for example by the XFree86 project. Its
1191 scope is similar to V4L2, an API to video capture and output devices for
1192 X clients. Xv allows applications to display live video in a window,
1193 send window contents to a TV output, and capture or output still images
1194 in XPixmaps [#f1]_. With their implementation XFree86 makes the extension
1195 available across many operating systems and architectures.
1197 Because the driver is embedded into the X server Xv has a number of
1198 advantages over the V4L2 :ref:`video overlay interface <overlay>`. The
1199 driver can easily determine the overlay target, i. e. visible graphics
1200 memory or off-screen buffers for a destructive overlay. It can program
1201 the RAMDAC for a non-destructive overlay, scaling or color-keying, or
1202 the clipping functions of the video capture hardware, always in sync
1203 with drawing operations or windows moving or changing their stacking
1206 To combine the advantages of Xv and V4L a special Xv driver exists in
1207 XFree86 and XOrg, just programming any overlay capable Video4Linux
1208 device it finds. To enable it ``/etc/X11/XF86Config`` must contain these
1217 As of XFree86 4.2 this driver still supports only V4L ioctls, however it
1218 should work just fine with all V4L2 devices through the V4L2
1219 backward-compatibility layer. Since V4L2 permits multiple opens it is
1220 possible (if supported by the V4L2 driver) to capture video while an X
1221 client requested video overlay. Restrictions of simultaneous capturing
1222 and overlay are discussed in :ref:`overlay` apply.
1224 Only marginally related to V4L2, XFree86 extended Xv to support hardware
1225 YUV to RGB conversion and scaling for faster video playback, and added
1226 an interface to MPEG-2 decoding hardware. This API is useful to display
1227 images captured with V4L2 devices.
1232 V4L2 does not support digital terrestrial, cable or satellite broadcast.
1233 A separate project aiming at digital receivers exists. You can find its
1234 homepage at `https://linuxtv.org <https://linuxtv.org>`__. The Linux
1235 DVB API has no connection to the V4L2 API except that drivers for hybrid
1236 hardware may support both.
1245 Experimental API Elements
1246 =========================
1248 The following V4L2 API elements are currently experimental and may
1249 change in the future.
1251 - :ref:`VIDIOC_DBG_G_REGISTER` and
1252 :ref:`VIDIOC_DBG_S_REGISTER <VIDIOC_DBG_G_REGISTER>` ioctls.
1254 - :ref:`VIDIOC_DBG_G_CHIP_INFO` ioctl.
1258 Obsolete API Elements
1259 =====================
1261 The following V4L2 API elements were superseded by new interfaces and
1262 should not be implemented in new drivers.
1264 - ``VIDIOC_G_MPEGCOMP`` and ``VIDIOC_S_MPEGCOMP`` ioctls. Use Extended
1265 Controls, :ref:`extended-controls`.
1267 - VIDIOC_G_DV_PRESET, VIDIOC_S_DV_PRESET,
1268 VIDIOC_ENUM_DV_PRESETS and VIDIOC_QUERY_DV_PRESET ioctls. Use
1269 the DV Timings API (:ref:`dv-timings`).
1271 - ``VIDIOC_SUBDEV_G_CROP`` and ``VIDIOC_SUBDEV_S_CROP`` ioctls. Use
1272 ``VIDIOC_SUBDEV_G_SELECTION`` and ``VIDIOC_SUBDEV_S_SELECTION``,
1273 :ref:`VIDIOC_SUBDEV_G_SELECTION`.
1276 This is not implemented in XFree86.
projects / linux-2.6-microblaze.git / blob