linux-kernel - Re: [PATCH v2 1/2] media: add RealVideo format

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Message-ID: <d841827840b0a33b424d91aea46af33d30f5de7c.camel@ndufresne.ca>
Date:   Thu, 12 Jan 2023 16:29:56 -0500
From:   Nicolas Dufresne <nicolas@...fresne.ca>
To:     Ming Qian <ming.qian@....com>, mchehab@...nel.org,
        hverkuil-cisco@...all.nl
Cc:     shawnguo@...nel.org, robh+dt@...nel.org, s.hauer@...gutronix.de,
        kernel@...gutronix.de, festevam@...il.com, linux-imx@....com,
        xiahong.bao@....com, eagle.zhou@....com, tao.jiang_2@....com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] media: add RealVideo format

Hi Ming,

Le jeudi 12 janvier 2023 à 17:18 +0800, Ming Qian a écrit :
> RealVideo, or also spelled as Real Video, is a suite of proprietary
> video compression formats developed by RealNetworks -
> the specific format changes with the version.
> RealVideo codecs are identified by four-character codes.
> RV10 and RV20 are the H.263-based codecs.
> RV30 and RV40 are RealNetworks' proprietary H.264-based codecs.
> RV60 is RealNetworks' proprietary HEVC-based codecs.
> 
> Signed-off-by: Ming Qian <ming.qian@....com>
> ---
>  .../userspace-api/media/v4l/pixfmt-compressed.rst     | 11 +++++++++++
>  drivers/media/v4l2-core/v4l2-ioctl.c                  |  1 +
>  include/uapi/linux/videodev2.h                        |  1 +
>  3 files changed, 13 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst b/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> index a0230f357680..22035d92c788 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-compressed.rst
> @@ -237,6 +237,17 @@ Compressed Formats
>          Metadata associated with the frame to decode is required to be passed
>          through the ``V4L2_CID_STATELESS_FWHT_PARAMS`` control.
>  	See the :ref:`associated Codec Control ID <codec-stateless-fwht>`.
> +    * .. _V4L2-PIX-FMT-RV:
> +
> +      - ``V4L2_PIX_FMT_RV``
> +      - 'RV00'
> +      - RealVideo, or also spelled as Real Video, is a suite of proprietary
> +        video compression formats developed by RealNetworks -
> +        the specific format changes with the version.
> +        RealVideo codecs are identified by four-character codes.
> +        RV10 and RV20 are the H.263-based codecs.
> +        RV30 and RV40 are RealNetworks' proprietary H.264-based codecs.
> +        RV60 is RealNetworks' proprietary HEVC-based codecs.

Much better description. Though you haven't commented or addressed my concern of
having 4 different CODECs under the same FMT. I thinks it would make more sense
to export the four of them. Then driver can pick the set they support,
regardless if it requires special handling of not at the HW level. What do you
think ?

Even though unlikely considering the age of the CODECs, but having a single FMT
for an encoder would just increase the encoder interface complexity (could
require a control to select which actual format to encode to).
>  
>  .. raw:: latex
>  
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 9b5b04b8aa69..c375261d169f 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -1473,6 +1473,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
>  		case V4L2_PIX_FMT_FWHT:		descr = "FWHT"; break; /* used in vicodec */
>  		case V4L2_PIX_FMT_FWHT_STATELESS:	descr = "FWHT Stateless"; break; /* used in vicodec */
>  		case V4L2_PIX_FMT_SPK:		descr = "Sorenson Spark"; break;
> +		case V4L2_PIX_FMT_RV:		descr = "RealVideo"; break;
>  		case V4L2_PIX_FMT_CPIA1:	descr = "GSPCA CPiA YUV"; break;
>  		case V4L2_PIX_FMT_WNVA:		descr = "WNVA"; break;
>  		case V4L2_PIX_FMT_SN9C10X:	descr = "GSPCA SN9C10X"; break;
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 262ef10cfa02..0a7ddb023d7c 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -740,6 +740,7 @@ 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_SPK      v4l2_fourcc('S', 'P', 'K', '0') /* Sorenson Spark */
> +#define V4L2_PIX_FMT_RV       v4l2_fourcc('R', 'V', '0', '0') /* RealVideo */
>  
>  /*  Vendor-specific formats   */
>  #define V4L2_PIX_FMT_CPIA1    v4l2_fourcc('C', 'P', 'I', 'A') /* cpia1 YUV */