linux-kernel - Re: [PATCH v5 05/10] media: v4l: Add definition for the Aspeed JPEG format

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Message-ID: <YZZIDNCLJXwrqY4W@paasikivi.fi.intel.com>
Date:   Thu, 18 Nov 2021 14:33:16 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Jammy Huang <jammy_huang@...eedtech.com>
Cc:     eajames@...ux.ibm.com, mchehab@...nel.org, joel@....id.au,
        andrew@...id.au, hverkuil-cisco@...all.nl,
        gregkh@...uxfoundation.org, laurent.pinchart@...asonboard.com,
        linux-media@...r.kernel.org, openbmc@...ts.ozlabs.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-aspeed@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 05/10] media: v4l: Add definition for the Aspeed JPEG
 format

Hi Jammy,

On Thu, Nov 18, 2021 at 03:40:26PM +0800, Jammy Huang wrote:
> This introduces support for the Aspeed JPEG format, where the new frame
> can refer to previous frame to reduce the amount of compressed data. The
> concept is similar to I/P frame of video compression. I will compare the
> new frame with previous one to decide which macroblock's data is
> changed, and only the changed macroblocks will be compressed.
> 
> This Aspeed JPEG format is used by the video engine on Aspeed platforms,
> which is generally adapted for remote KVM.
> 
> Signed-off-by: Jammy Huang <jammy_huang@...eedtech.com>
> ---
> v5:
>   - no update
> v4:
>   - new
> ---
>  Documentation/media/uapi/v4l/pixfmt-reserved.rst | 12 ++++++++++++
>  drivers/media/v4l2-core/v4l2-ioctl.c             |  1 +
>  include/uapi/linux/videodev2.h                   |  1 +
>  3 files changed, 14 insertions(+)
> 
> diff --git a/Documentation/media/uapi/v4l/pixfmt-reserved.rst b/Documentation/media/uapi/v4l/pixfmt-reserved.rst
> index b2cd155e691b..23c05063133d 100644
> --- a/Documentation/media/uapi/v4l/pixfmt-reserved.rst
> +++ b/Documentation/media/uapi/v4l/pixfmt-reserved.rst
> @@ -264,6 +264,18 @@ please make a proposal on the linux-media mailing list.
>  	of tiles, resulting in 32-aligned resolutions for the luminance plane
>  	and 16-aligned resolutions for the chrominance plane (with 2x2
>  	subsampling).
> +    * .. _V4L2-PIX-FMT-AJPG:
> +
> +      - ``V4L2_PIX_FMT_AJPG``
> +      - 'AJPG'
> +      - ASPEED JPEG format used by the aspeed-video driver on Aspeed platforms,
> +        which is generally adapted for remote KVM.
> +        On each frame compression, I will compare the new frame with previous
> +        one to decide which macroblock's data is changed, and only the changed
> +        macroblocks will be compressed.
> +
> +        You could reference to chapter 36, Video Engine, of AST2600's datasheet
> +        for more information.

Is this datasheet publicly available? Do you have a URL?

-- 
Regards,

Sakari Ailus