Messages in this thread | | | Date | Wed, 26 Oct 2022 10:42:09 +0800 | Subject | Re: [PATCH v10 3/5] media: Documentation: aspeed-video: Add user documentation for the aspeed-video driver | From | Jammy Huang <> |
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Hi Nicolas,
Thanks for your comments.
On 2022/10/25 下午 09:18, Nicolas Dufresne wrote: > Hi Jammy, > > thanks for the addition. > > Le mardi 25 octobre 2022 à 17:02 +0800, Jammy Huang a écrit : >> Add user documentation for the aspeed-video driver. >> >> Signed-off-by: Jammy Huang <jammy_huang@aspeedtech.com> >> --- >> v10: >> - new >> --- >> .../media/drivers/aspeed-video.rst | 61 +++++++++++++++++++ >> .../userspace-api/media/drivers/index.rst | 1 + >> 2 files changed, 62 insertions(+) >> create mode 100644 Documentation/userspace-api/media/drivers/aspeed-video.rst >> >> diff --git a/Documentation/userspace-api/media/drivers/aspeed-video.rst b/Documentation/userspace-api/media/drivers/aspeed-video.rst >> new file mode 100644 >> index 000000000000..798a2588b175 >> --- /dev/null >> +++ b/Documentation/userspace-api/media/drivers/aspeed-video.rst >> @@ -0,0 +1,61 @@ >> +.. 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. > I think some of the information disclosed in the following quote could be > summarized. Notably the part about the extra buffers. > > Aspeed JPEG Format requires an additional buffer, called bcd, to store > the information about which macro block in the new frame is different > from the previous one. > > To have bcd correctly working, we need to swap the buffers for src0/1 to > make src1 refer to previous frame and src0 to the coming new frame. > > But before I push you this route, have you considered using a dedicated pixel > format instead ? Here's my thinking, the output of the JPEG encoder is no longer > "compatible" (or at least won't yield the expected images) if used with a normal > JPEG decoder. By differentiating these two as dedicated formats, you will only need > 1 vendor control, and you avoid the potential risk of software bugs mixing them up. > Also note that there is other JPEG based vendor formats that exist in V4L2. > > Let me know what do you think ?
Yes, I also add a dedicated formats, V4L2_PIX_FMT_AJPG, in this series. In [PATCH v10 1/5]
media: v4l: Add definition for the Aspeed JPEG format, I add the description in pixfmt-reserved.rst.
After this series applied, the users can choose either of these two formats by VIDIOC_S_FMT as
per their preference.
> > Nicolas > >> + >> +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. >> diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst >> index 32f82aed47d9..46a494e00b72 100644 >> --- a/Documentation/userspace-api/media/drivers/index.rst >> +++ b/Documentation/userspace-api/media/drivers/index.rst >> @@ -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
-- Best Regards Jammy
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