linux-kernel - Re: [PATCH v2 1/5] media: uapi: videodev2: Add support for AV1 stateful decoder

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Message-ID: <c2acbc028d014ca9eccefc070e50e40a1022f90c.camel@ndufresne.ca>
Date: Fri, 17 Oct 2025 16:01:59 -0400
From: Nicolas Dufresne <nicolas@...fresne.ca>
To: Deepa Guthyappa Madivalara <deepa.madivalara@....qualcomm.com>, Mauro
 Carvalho Chehab <mchehab@...nel.org>, Vikash Garodia
 <vikash.garodia@....qualcomm.com>, Dikshita Agarwal	
 <dikshita.agarwal@....qualcomm.com>, Abhinav Kumar
 <abhinav.kumar@...ux.dev>,  Bryan O'Donoghue	 <bod@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-msm@...r.kernel.org, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH v2 1/5] media: uapi: videodev2: Add support for AV1
 stateful decoder

Le vendredi 17 octobre 2025 à 11:35 -0700, Deepa Guthyappa Madivalara a écrit :
> Introduce a new pixel format, V4L2_PIX_FMT_AV1, to the
> Video4Linux2(V4L2) API. This format is intended for AV1
> bitstreams in stateful decoding/encoding workflows.
> The fourcc code 'AV10' is used to distinguish
> this format from the existing V4L2_PIX_FMT_AV1_FRAME,
> which is used for stateless AV1 decoder implementation.
> 
> Signed-off-by: Deepa Guthyappa Madivalara <deepa.madivalara@....qualcomm.com>
> ---
>  Documentation/userspace-api/media/v4l/pixfmt-compressed.rst | 8 ++++++++
>  include/uapi/linux/videodev2.h                              | 1 +
>  2 files changed, 9 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst b/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> index 806ed73ac474ce0e6df00f902850db9fd0db240e..d82557a6ac30851b4fd432a5ceab969abaed2e25 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> @@ -274,6 +274,14 @@ Compressed Formats
>          of macroblocks to decode a full corresponding frame to the matching
>          capture buffer.
>  
> +    * .. _V4L2-PIX-FMT-AV1:
> +
> +      - ``V4L2_PIX_FMT_AV1``
> +      - 'AV10'
> +      - AV1 compressed video frame. This format is adapted for implementing AV1
> +        pipeline. The decoder implements stateful video decoder and expects one
> +        Temporal Unit per buffer from OBU-stream or AnnexB.
> +        The encoder generates one Temporal Unit per buffer.
>  .. raw:: latex
>  
>      \normalsize
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index becd08fdbddb857f8f2bf205d2164dc6e20e80b2..e03cfe0a5ae830595f0bf69b951ca16beaedab72 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -775,6 +775,7 @@ struct v4l2_pix_format {
>  #define V4L2_PIX_FMT_H264_SLICE v4l2_fourcc('S', '2', '6', '4') /* H264 parsed slices */
>  #define V4L2_PIX_FMT_HEVC_SLICE v4l2_fourcc('S', '2', '6', '5') /* HEVC parsed slices */
>  #define V4L2_PIX_FMT_AV1_FRAME v4l2_fourcc('A', 'V', '1', 'F') /* AV1 parsed frame */
> +#define V4L2_PIX_FMT_AV1      v4l2_fourcc('A', 'V', '1', '0') /* AV1 */

An alternative fourcc could be to match the one used in the ISO specification,
which is also what browsers and Android uses. It would be "av01", link to the
spec:

http://downloads.aomedia.org/assets/pdf/AV1-ISO-Base-Media-File-Format-Binding-Specification.pdf

Though, we never had any requirement in this direction, its just an idea. With
or without, I'm happy with the definition.

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@...labora.com>

cheers,
Nicolas

>  #define V4L2_PIX_FMT_SPK      v4l2_fourcc('S', 'P', 'K', '0') /* Sorenson Spark */
>  #define V4L2_PIX_FMT_RV30     v4l2_fourcc('R', 'V', '3', '0') /* RealVideo 8 */
>  #define V4L2_PIX_FMT_RV40     v4l2_fourcc('R', 'V', '4', '0') /* RealVideo 9 & 10 */

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