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

Hans Verkuil
2019-08-14T08:11:46Z

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@collabora.com>
> Tested-by: Philipp Zabel <p.zabel@pengutronix.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
>