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1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later2 3.. _planar-apis:4 5*****************************6Single- and multi-planar APIs7*****************************8 9Some devices require data for each input or output video frame to be10placed in discontiguous memory buffers. In such cases, one video frame11has to be addressed using more than one memory address, i.e. one pointer12per "plane". A plane is a sub-buffer of the current frame. For examples13of such formats see :ref:`pixfmt`.14 15Initially, V4L2 API did not support multi-planar buffers and a set of16extensions has been introduced to handle them. Those extensions17constitute what is being referred to as the "multi-planar API".18 19Some of the V4L2 API calls and structures are interpreted differently,20depending on whether single- or multi-planar API is being used. An21application can choose whether to use one or the other by passing a22corresponding buffer type to its ioctl calls. Multi-planar versions of23buffer types are suffixed with an ``_MPLANE`` string. For a list of24available multi-planar buffer types see enum25:c:type:`v4l2_buf_type`.26 27 28Multi-planar formats29====================30 31Multi-planar API introduces new multi-planar formats. Those formats use32a separate set of FourCC codes. It is important to distinguish between33the multi-planar API and a multi-planar format. Multi-planar API calls34can handle all single-planar formats as well (as long as they are passed35in multi-planar API structures), while the single-planar API cannot36handle multi-planar formats.37 38 39Calls that distinguish between single and multi-planar APIs40===========================================================41 42:ref:`VIDIOC_QUERYCAP <VIDIOC_QUERYCAP>`43 Two additional multi-planar capabilities are added. They can be set44 together with non-multi-planar ones for devices that handle both45 single- and multi-planar formats.46 47:ref:`VIDIOC_G_FMT <VIDIOC_G_FMT>`, :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>`, :ref:`VIDIOC_TRY_FMT <VIDIOC_G_FMT>`48 New structures for describing multi-planar formats are added: struct49 :c:type:`v4l2_pix_format_mplane` and50 struct :c:type:`v4l2_plane_pix_format`.51 Drivers may define new multi-planar formats, which have distinct52 FourCC codes from the existing single-planar ones.53 54:ref:`VIDIOC_QBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>`, :ref:`VIDIOC_QUERYBUF <VIDIOC_QUERYBUF>`55 A new struct :c:type:`v4l2_plane` structure for56 describing planes is added. Arrays of this structure are passed in57 the new ``m.planes`` field of struct58 :c:type:`v4l2_buffer`.59 60:ref:`VIDIOC_REQBUFS <VIDIOC_REQBUFS>`61 Will allocate multi-planar buffers as requested.62