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author | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 11:40:06 -0300 |
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committer | Mauro Carvalho Chehab <mchehab@s-opensource.com> | 2016-07-08 11:59:40 -0300 |
commit | 60c2820d0f6d3497975b6488e2599f8f611d8b95 (patch) | |
tree | b3b03707c6438ea9b99cc57e847ebf517f968ab1 /Documentation/media/uapi/v4l/planar-apis.rst | |
parent | a97369b5e21ea9b8b5fef7c0f4f48bbe60c07ca3 (diff) | |
download | linux-60c2820d0f6d3497975b6488e2599f8f611d8b95.tar.bz2 |
doc_rst: rename the media Sphinx suff to Documentation/media
The name of the subsystem is "media", and not "linux_tv". Also,
as we plan to add other stuff there in the future, let's
rename also the media uAPI book to media_uapi, to make it
clearer.
No functional changes.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Diffstat (limited to 'Documentation/media/uapi/v4l/planar-apis.rst')
-rw-r--r-- | Documentation/media/uapi/v4l/planar-apis.rst | 61 |
1 files changed, 61 insertions, 0 deletions
diff --git a/Documentation/media/uapi/v4l/planar-apis.rst b/Documentation/media/uapi/v4l/planar-apis.rst new file mode 100644 index 000000000000..5fe2e1188230 --- /dev/null +++ b/Documentation/media/uapi/v4l/planar-apis.rst @@ -0,0 +1,61 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _planar-apis: + +***************************** +Single- and multi-planar APIs +***************************** + +Some devices require data for each input or output video frame to be +placed in discontiguous memory buffers. In such cases, one video frame +has to be addressed using more than one memory address, i.e. one pointer +per "plane". A plane is a sub-buffer of the current frame. For examples +of such formats see :ref:`pixfmt`. + +Initially, V4L2 API did not support multi-planar buffers and a set of +extensions has been introduced to handle them. Those extensions +constitute what is being referred to as the "multi-planar API". + +Some of the V4L2 API calls and structures are interpreted differently, +depending on whether single- or multi-planar API is being used. An +application can choose whether to use one or the other by passing a +corresponding buffer type to its ioctl calls. Multi-planar versions of +buffer types are suffixed with an ``_MPLANE`` string. For a list of +available multi-planar buffer types see enum +:ref:`v4l2_buf_type <v4l2-buf-type>`. + + +Multi-planar formats +==================== + +Multi-planar API introduces new multi-planar formats. Those formats use +a separate set of FourCC codes. It is important to distinguish between +the multi-planar API and a multi-planar format. Multi-planar API calls +can handle all single-planar formats as well (as long as they are passed +in multi-planar API structures), while the single-planar API cannot +handle multi-planar formats. + + +Calls that distinguish between single and multi-planar APIs +=========================================================== + +:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>` + Two additional multi-planar capabilities are added. They can be set + together with non-multi-planar ones for devices that handle both + single- and multi-planar formats. + +:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`, :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>` + New structures for describing multi-planar formats are added: struct + :ref:`v4l2_pix_format_mplane <v4l2-pix-format-mplane>` and + struct :ref:`v4l2_plane_pix_format <v4l2-plane-pix-format>`. + Drivers may define new multi-planar formats, which have distinct + FourCC codes from the existing single-planar ones. + +:ref:`VIDIOC_QBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>` + A new struct :ref:`v4l2_plane <v4l2-plane>` structure for + describing planes is added. Arrays of this structure are passed in + the new ``m.planes`` field of struct + :ref:`v4l2_buffer <v4l2-buffer>`. + +:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>` + Will allocate multi-planar buffers as requested. |