1. 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.
The ASPEED video driver implements the following driver-specific control:
1.1. 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.
(0) |
ASPEED HQ mode is disabled. |
(1) |
ASPEED HQ mode is enabled. |
1.2. 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.
(1) |
minimum |
(12) |
maximum |
(1) |
step |
(1) |
default |
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