| .. 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. |
