mirror of https://gitee.com/openkylin/linux.git
254 lines
3.4 KiB
ReStructuredText
254 lines
3.4 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _V4L2-PIX-FMT-YUV420M:
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.. _v4l2-pix-fmt-yvu420m:
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************************************************************
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V4L2_PIX_FMT_YUV420M ('YM12'), V4L2_PIX_FMT_YVU420M ('YM21')
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************************************************************
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V4L2_PIX_FMT_YVU420M
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Variation of ``V4L2_PIX_FMT_YUV420`` and ``V4L2_PIX_FMT_YVU420`` with
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planes non contiguous in memory.
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Description
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===========
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This is a multi-planar format, as opposed to a packed format. The three
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components are separated into three sub-images or planes.
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The Y plane is first. The Y plane has one byte per pixel. For
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``V4L2_PIX_FMT_YUV420M`` the Cb data constitutes the second plane which
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is half the width and half the height of the Y plane (and of the image).
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Each Cb belongs to four pixels, a two-by-two square of the image. For
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example, Cb\ :sub:`0` belongs to Y'\ :sub:`00`, Y'\ :sub:`01`,
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Y'\ :sub:`10`, and Y'\ :sub:`11`. The Cr data, just like the Cb plane,
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is in the third plane.
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``V4L2_PIX_FMT_YVU420M`` is the same except the Cr data is stored in the
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second plane and the Cb data in the third plane.
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If the Y plane has pad bytes after each row, then the Cb and Cr planes
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have half as many pad bytes after their rows. In other words, two Cx
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rows (including padding) is exactly as long as one Y row (including
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padding).
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``V4L2_PIX_FMT_YUV420M`` and ``V4L2_PIX_FMT_YVU420M`` are intended to be
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used only in drivers and applications that support the multi-planar API,
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described in :ref:`planar-apis`.
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**Byte Order.**
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Each cell is one byte.
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.. flat-table::
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:header-rows: 0
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:stub-columns: 0
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- .. row 1
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- start0 + 0:
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- Y'\ :sub:`00`
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- Y'\ :sub:`01`
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- Y'\ :sub:`02`
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- Y'\ :sub:`03`
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- .. row 2
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- start0 + 4:
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- Y'\ :sub:`10`
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- Y'\ :sub:`11`
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- Y'\ :sub:`12`
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- Y'\ :sub:`13`
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- .. row 3
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- start0 + 8:
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- Y'\ :sub:`20`
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- Y'\ :sub:`21`
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- Y'\ :sub:`22`
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- Y'\ :sub:`23`
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- .. row 4
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- start0 + 12:
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- Y'\ :sub:`30`
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- Y'\ :sub:`31`
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- Y'\ :sub:`32`
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- Y'\ :sub:`33`
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- .. row 5
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-
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- .. row 6
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- start1 + 0:
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- Cb\ :sub:`00`
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- Cb\ :sub:`01`
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- .. row 7
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- start1 + 2:
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- Cb\ :sub:`10`
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- Cb\ :sub:`11`
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- .. row 8
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-
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- .. row 9
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- start2 + 0:
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- Cr\ :sub:`00`
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- Cr\ :sub:`01`
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- .. row 10
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- start2 + 2:
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- Cr\ :sub:`10`
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- Cr\ :sub:`11`
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**Color Sample Location..**
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.. flat-table::
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:header-rows: 0
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:stub-columns: 0
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- .. row 1
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-
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- 0
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-
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- 1
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-
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- 2
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-
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- 3
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- .. row 2
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- 0
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- Y
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-
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- Y
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-
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- Y
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-
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- Y
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- .. row 3
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-
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-
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- C
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-
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-
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-
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- C
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-
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- .. row 4
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- 1
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- Y
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-
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- Y
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-
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- Y
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-
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- Y
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- .. row 5
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-
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- .. row 6
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- 2
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- Y
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-
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- Y
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-
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- Y
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-
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- Y
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- .. row 7
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-
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-
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- C
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-
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-
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-
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- C
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-
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- .. row 8
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- 3
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- Y
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-
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- Y
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-
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- Y
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-
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- Y
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