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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
`github <https://github.com/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.
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