linux-kernel - Re: [PATCH v5 04/11] media: uapi: h264: Add the concept of start code

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Date:   Wed, 14 Aug 2019 10:11:04 +0200
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Ezequiel Garcia <ezequiel@...labora.com>,
        linux-media@...r.kernel.org
Cc:     kernel@...labora.com,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Tomasz Figa <tfiga@...omium.org>,
        linux-rockchip@...ts.infradead.org,
        Heiko Stuebner <heiko@...ech.de>,
        Jonas Karlman <jonas@...boo.se>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Alexandre Courbot <acourbot@...omium.org>,
        fbuergisser@...omium.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 04/11] media: uapi: h264: Add the concept of start code

On 8/12/19 9:35 PM, Ezequiel Garcia wrote:
> Stateless decoders have different expectations about the
> start code that is prepended on H264 slices. Add a
> menu control to express the supported start code types
> (including no start code).
> 
> Drivers are allowed to support only one start code type,
> but they can support both too.
> 
> Note that this is independent of the H264 decoding mode,
> which specifies the granularity of the decoding operations.
> Either in frame-based or slice-based mode, this new control
> will allow to define the start code expected on H264 slices.
> 
> Signed-off-by: Ezequiel Garcia <ezequiel@...labora.com>
> Tested-by: Philipp Zabel <p.zabel@...gutronix.de>
> ---
> Changes in v5:
> * Improve specification as suggested by Hans.
> Changes in v4:
> * New patch.
> ---
>  .../media/uapi/v4l/ext-ctrls-codec.rst        | 33 +++++++++++++++++++
>  .../media/uapi/v4l/pixfmt-compressed.rst      |  3 +-
>  drivers/media/v4l2-core/v4l2-ctrls.c          |  9 +++++
>  include/media/h264-ctrls.h                    |  6 ++++
>  4 files changed, 50 insertions(+), 1 deletion(-)
> 

<snip>

> diff --git a/include/media/h264-ctrls.h b/include/media/h264-ctrls.h
> index e6c510877f67..31555c99f64a 100644
> --- a/include/media/h264-ctrls.h
> +++ b/include/media/h264-ctrls.h
> @@ -27,6 +27,7 @@
>  #define V4L2_CID_MPEG_VIDEO_H264_SLICE_PARAMS	(V4L2_CID_MPEG_BASE+1003)
>  #define V4L2_CID_MPEG_VIDEO_H264_DECODE_PARAMS	(V4L2_CID_MPEG_BASE+1004)
>  #define V4L2_CID_MPEG_VIDEO_H264_DECODING_MODE	(V4L2_CID_MPEG_BASE+1005)
> +#define V4L2_CID_MPEG_VIDEO_H264_STARTCODE	(V4L2_CID_MPEG_BASE+1006)

I almost forgot: can you change this to _START_CODE? Since it is two words?

Thanks!

	Hans

>  
>  /* enum v4l2_ctrl_type type values */
>  #define V4L2_CTRL_TYPE_H264_SPS			0x0110
> @@ -41,6 +42,11 @@ enum v4l2_mpeg_video_h264_decoding_mode {
>  	V4L2_MPEG_VIDEO_H264_FRAME_BASED_DECODING,
>  };
>  
> +enum v4l2_mpeg_video_h264_start_code {
> +	V4L2_MPEG_VIDEO_H264_NO_STARTCODE,
> +	V4L2_MPEG_VIDEO_H264_ANNEX_B_STARTCODE,
> +};
> +
>  #define V4L2_H264_SPS_CONSTRAINT_SET0_FLAG			0x01
>  #define V4L2_H264_SPS_CONSTRAINT_SET1_FLAG			0x02
>  #define V4L2_H264_SPS_CONSTRAINT_SET2_FLAG			0x04
>