1.. SPDX-License-Identifier: GPL-2.0
2
3.. include:: <isonum.txt>
4
5ASPEED video driver
6===================
7
8ASPEED Video Engine found on AST2400/2500/2600 SoC supports high performance
9video compressions with a wide range of video quality and compression ratio
10options. The adopted compressing algorithm is a modified JPEG algorithm.
11
12There are 2 types of compressions in this IP.
13
14* JPEG JFIF standard mode: for single frame and management compression
15* ASPEED proprietary mode: for multi-frame and differential compression.
16  Support 2-pass (high quality) video compression scheme (Patent pending by
17  ASPEED). Provide visually lossless video compression quality or to reduce
18  the network average loading under intranet KVM applications.
19
20VIDIOC_S_FMT can be used to choose which format you want. V4L2_PIX_FMT_JPEG
21stands for JPEG JFIF standard mode; V4L2_PIX_FMT_AJPG stands for ASPEED
22proprietary mode.
23
24More details on the ASPEED video hardware operations can be found in
25*chapter 6.2.16 KVM Video Driver* of SDK_User_Guide which available on
26`github <https://github.com/AspeedTech-BMC/openbmc/releases/>`__.
27
28The ASPEED video driver implements the following driver-specific control:
29
30``V4L2_CID_ASPEED_HQ_MODE``
31---------------------------
32    Enable/Disable ASPEED's High quality mode. This is a private control
33    that can be used to enable high quality for aspeed proprietary mode.
34
35.. flat-table::
36    :header-rows:  0
37    :stub-columns: 0
38    :widths:       1 4
39
40    * - ``(0)``
41      - ASPEED HQ mode is disabled.
42    * - ``(1)``
43      - ASPEED HQ mode is enabled.
44
45``V4L2_CID_ASPEED_HQ_JPEG_QUALITY``
46-----------------------------------
47    Define the quality of ASPEED's High quality mode. This is a private control
48    that can be used to decide compression quality if High quality mode enabled
49    . Higher the value, better the quality and bigger the size.
50
51.. flat-table::
52    :header-rows:  0
53    :stub-columns: 0
54    :widths:       1 4
55
56    * - ``(1)``
57      - minimum
58    * - ``(12)``
59      - maximum
60    * - ``(1)``
61      - step
62    * - ``(1)``
63      - default
64
65**Copyright** |copy| 2022 ASPEED Technology Inc.
66