diff options
Diffstat (limited to 'Documentation/userspace-api/media/v4l/diff-v4l.rst')
| -rw-r--r-- | Documentation/userspace-api/media/v4l/diff-v4l.rst | 39 |
1 files changed, 6 insertions, 33 deletions
diff --git a/Documentation/userspace-api/media/v4l/diff-v4l.rst b/Documentation/userspace-api/media/v4l/diff-v4l.rst index 3f7bac44377c..caa05fbbd396 100644 --- a/Documentation/userspace-api/media/v4l/diff-v4l.rst +++ b/Documentation/userspace-api/media/v4l/diff-v4l.rst @@ -1,4 +1,5 @@ .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later +.. c:namespace:: V4L .. _diff-v4l: @@ -13,7 +14,6 @@ the much improved V4L2 API replaces the V4L API. The support for the old V4L calls were removed from Kernel, but the library :ref:`libv4l` supports the conversion of a V4L API system call into a V4L2 one. - Opening and Closing Devices =========================== @@ -32,7 +32,6 @@ recommend that V4L2 drivers by default register devices with the same numbers, but the system administrator can assign arbitrary minor numbers using driver module options. The major device number remains 81. - .. _v4l-dev: .. flat-table:: V4L Device Types, Names and Numbers @@ -53,14 +52,12 @@ using driver module options. The major device number remains 81. - ``/dev/vbi``, ``/dev/vbi0`` to ``/dev/vbi31`` - 224-255 - V4L prohibits (or used to prohibit) multiple opens of a device file. V4L2 drivers *may* support multiple opens, see :ref:`open` for details and consequences. V4L drivers respond to V4L2 ioctls with an ``EINVAL`` error code. - Querying Capabilities ===================== @@ -151,7 +148,6 @@ introduction. - ``-`` - See above. - The ``audios`` field was replaced by ``capabilities`` flag ``V4L2_CAP_AUDIO``, indicating *if* the device has any audio inputs or outputs. To determine their number applications can enumerate audio @@ -164,7 +160,6 @@ were removed. Calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` or dimensions returns the closest size possible, taking into account the current video standard, cropping and scaling limitations. - Video Sources ============= @@ -180,7 +175,6 @@ The ``channel`` field counting inputs was renamed to ``index``, the video input types were renamed as follows: - .. flat-table:: :header-rows: 1 :stub-columns: 0 @@ -192,7 +186,6 @@ video input types were renamed as follows: * - ``VIDEO_TYPE_CAMERA`` - ``V4L2_INPUT_TYPE_CAMERA`` - Unlike the ``tuners`` field expressing the number of tuners of this input, V4L2 assumes each video input is connected to at most one tuner. However a tuner can have more than one input, i. e. RF connectors, and a @@ -216,7 +209,6 @@ addition together with the ``norm`` field and has been removed in the meantime. V4L2 has a similar, albeit more comprehensive approach to video standards, see :ref:`standard` for more information. - Tuning ====== @@ -260,7 +252,6 @@ frequency where renamed to to a struct :c:type:`v4l2_frequency` instead of an unsigned long integer. - .. _v4l-image-properties: Image Properties @@ -274,7 +265,6 @@ replaced by V4L2 controls accessible with the :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls: - .. flat-table:: :header-rows: 1 :stub-columns: 0 @@ -292,7 +282,6 @@ replaced by V4L2 controls accessible with the * - ``whiteness`` - ``V4L2_CID_WHITENESS`` - The V4L picture controls are assumed to range from 0 to 65535 with no particular reset value. The V4L2 API permits arbitrary limits and defaults which can be queried with the @@ -306,7 +295,6 @@ of the image depth and others need not know. The ``palette`` field moved into the struct :c:type:`v4l2_pix_format`: - .. flat-table:: :header-rows: 1 :stub-columns: 0 @@ -346,11 +334,9 @@ into the struct :c:type:`v4l2_pix_format`: * - ``VIDEO_PALETTE_YUV410P`` - :ref:`V4L2_PIX_FMT_YVU410 <V4L2-PIX-FMT-YVU410>` - V4L2 image formats are defined in :ref:`pixfmt`. The image format can be selected with the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. - Audio ===== @@ -384,7 +370,6 @@ The following fields where replaced by V4L2 controls accessible with the :ref:`VIDIOC_S_CTRL <VIDIOC_G_CTRL>` ioctls: - .. flat-table:: :header-rows: 1 :stub-columns: 0 @@ -400,7 +385,6 @@ The following fields where replaced by V4L2 controls accessible with the * - ``balance`` - ``V4L2_CID_AUDIO_BALANCE`` - To determine which of these controls are supported by a driver V4L provides the ``flags`` ``VIDEO_AUDIO_VOLUME``, ``VIDEO_AUDIO_BASS``, ``VIDEO_AUDIO_TREBLE`` and ``VIDEO_AUDIO_BALANCE``. In the V4L2 API the @@ -416,7 +400,6 @@ V4L2 API permits arbitrary limits and defaults which can be queried with the :ref:`VIDIOC_QUERYCTRL` ioctl. For general information about controls see :ref:`control`. - Frame Buffer Overlay ==================== @@ -463,7 +446,6 @@ size is determined by ``w.width`` and ``w.height``. The ``VIDIOCCAPTURE`` ioctl to enable or disable overlay was renamed to :ref:`VIDIOC_OVERLAY`. - Cropping ======== @@ -490,21 +472,19 @@ struct :c:type:`v4l2_window`. These structures are used to select a capture or overlay format with the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl. - Reading Images, Memory Mapping ============================== - Capturing using the read method ------------------------------- There is no essential difference between reading images from a V4L or -V4L2 device using the :ref:`read() <func-read>` function, however V4L2 +V4L2 device using the :c:func:`read()` function, however V4L2 drivers are not required to support this I/O method. Applications can determine if the function is available with the :ref:`VIDIOC_QUERYCAP` ioctl. All V4L2 devices exchanging data with applications must support the -:ref:`select() <func-select>` and :ref:`poll() <func-poll>` +:c:func:`select()` and :c:func:`poll()` functions. To select an image format and size, V4L provides the ``VIDIOCSPICT`` and @@ -517,7 +497,6 @@ negotiation ioctls :ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>` and For more information about the V4L2 read interface see :ref:`rw`. - Capturing using memory mapping ------------------------------ @@ -528,7 +507,6 @@ read method. V4L2 supports memory mapping as well, with a few differences. - .. flat-table:: :header-rows: 1 :stub-columns: 0 @@ -550,7 +528,7 @@ differences. ``VIDIOCGMBUF`` ioctl is available to query the number of buffers, the offset of each buffer from the start of the virtual file, and the overall amount of memory used, which can be used as arguments - for the :ref:`mmap() <func-mmap>` function. + for the :c:func:`mmap()` function. - Buffers are individually mapped. The offset and size of each buffer can be determined with the :ref:`VIDIOC_QUERYBUF` ioctl. @@ -568,7 +546,7 @@ differences. the incoming queue. Filled buffers are dequeued from the outgoing queue with the :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl. To wait until filled buffers become available this function, - :ref:`select() <func-select>` or :ref:`poll() <func-poll>` can + :c:func:`select()` or :c:func:`poll()` can be used. The :ref:`VIDIOC_STREAMON` ioctl must be called once after enqueuing one or more buffers to start capturing. Its counterpart @@ -577,11 +555,9 @@ differences. signal status, if known, with the :ref:`VIDIOC_ENUMINPUT` ioctl. - For a more in-depth discussion of memory mapping and examples, see :ref:`mmap`. - Reading Raw VBI Data ==================== @@ -592,7 +568,6 @@ the V4L VBI interface. Reading from the device yields a raw VBI image with the following parameters: - .. flat-table:: :header-rows: 1 :stub-columns: 0 @@ -616,7 +591,6 @@ with the following parameters: * - flags - 0 - Undocumented in the V4L specification, in Linux 2.3 the ``VIDIOCGVBIFMT`` and ``VIDIOCSVBIFMT`` ioctls using struct ``vbi_format`` were added to determine the VBI image @@ -630,11 +604,10 @@ remaining fields are probably equivalent to struct Apparently only the Zoran (ZR 36120) driver implements these ioctls. The semantics differ from those specified for V4L2 in two ways. The -parameters are reset on :ref:`open() <func-open>` and +parameters are reset on :c:func:`open()` and ``VIDIOCSVBIFMT`` always returns an ``EINVAL`` error code if the parameters are invalid. - Miscellaneous ============= |