Commit dae86bb6 authored by Jammy Huang's avatar Jammy Huang Committed by Hans Verkuil
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media: Documentation: aspeed-video: Add user documentation for the aspeed-video driver 



Add user documentation for the aspeed-video driver.

Signed-off-by: default avatarJammy Huang <jammy_huang@aspeedtech.com>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
parent 867d3b27

Documentation/userspace-api/media/drivers/aspeed-video.rst

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.. SPDX-License-Identifier: GPL-2.0



.. include:: <isonum.txt>



ASPEED video driver

===================



ASPEED Video Engine found on AST2400/2500/2600 SoC supports high performance

video compressions with a wide range of video quality and compression ratio

options. The adopted compressing algorithm is a modified JPEG algorithm.



There are 2 types of compressions in this IP.



* JPEG JFIF standard mode: for single frame and management compression

* ASPEED proprietary mode: for multi-frame and differential compression.

  Support 2-pass (high quality) video compression scheme (Patent pending by

  ASPEED). Provide visually lossless video compression quality or to reduce

  the network average loading under intranet KVM applications.



VIDIOC_S_FMT can be used to choose which format you want. V4L2_PIX_FMT_JPEG

stands for JPEG JFIF standard mode; V4L2_PIX_FMT_AJPG stands for ASPEED

proprietary mode.



More details on the ASPEED video hardware operations can be found in

*chapter 6.2.16 KVM Video Driver* of SDK_User_Guide which available on

AspeedTech-BMC/openbmc/releases.



The ASPEED video driver implements the following driver-specific control:



``V4L2_CID_ASPEED_HQ_MODE``

---------------------------

    Enable/Disable ASPEED's High quality mode. This is a private control

    that can be used to enable high quality for aspeed proprietary mode.



.. flat-table::

    :header-rows:  0

    :stub-columns: 0

    :widths:       1 4



    * - ``(0)``

      - ASPEED HQ mode is disabled.

    * - ``(1)``

      - ASPEED HQ mode is enabled.



``V4L2_CID_ASPEED_HQ_JPEG_QUALITY``

-----------------------------------

    Define the quality of ASPEED's High quality mode. This is a private control

    that can be used to decide compression quality if High quality mode enabled

    . Higher the value, better the quality and bigger the size.



.. flat-table::

    :header-rows:  0

    :stub-columns: 0

    :widths:       1 4



    * - ``(1)``

      - minimum

    * - ``(12)``

      - maximum

    * - ``(1)``

      - step

    * - ``(1)``

      - default



**Copyright** |copy| 2022 ASPEED Technology Inc.

Documentation/userspace-api/media/drivers/index.rst

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@@ -31,6 +31,7 @@ For more details see the file COPYING in the source distribution of Linux. 
	:maxdepth: 5

	:numbered:



	aspeed-video

	ccs

	cx2341x-uapi

	dw100