linux-kernel - Re: [PATCH v2 1/4] media: v4l2-ctrls: Add intra-refresh period control

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Message-ID: <6eb7ea37-e460-2884-9e07-6ff6f9a15414@xs4all.nl>
Date:   Tue, 12 Jan 2021 11:05:09 +0100
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Cc:     Ezequiel Garcia <ezequiel@...labora.com>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Maheshwar Ajja <majja@...eaurora.org>
Subject: Re: [PATCH v2 1/4] media: v4l2-ctrls: Add intra-refresh period
 control

On 06/12/2020 11:27, Stanimir Varbanov wrote:
> Add a control to set intra-refresh period.
> 
> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
> ---
>  .../userspace-api/media/v4l/ext-ctrls-codec.rst       | 11 +++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls.c                  |  2 ++
>  include/uapi/linux/v4l2-controls.h                    |  1 +
>  3 files changed, 14 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 454ecd9a0f83..d65d7c1381b7 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -1104,6 +1104,17 @@ enum v4l2_mpeg_video_h264_entropy_mode -
>      macroblocks is refreshed until the cycle completes and starts from
>      the top of the frame. Applicable to H264, H263 and MPEG4 encoder.
>  
> +``V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD (integer)``
> +    Intra macroblock refresh period. This sets the period to refresh
> +    the whole frame. With other words, this defines the number of frames

With -> In

> +    for which the whole frame will be intra-refreshed.  An example:
> +    setting period to 1 means that the whole frame will be refreshed,
> +    setting period to 2 means that the half of macroblocks will be
> +    intra-refreshed on frameX and the other half of macroblocks
> +    will be refreshed in frameX + 1 and so on. Setting period to zero
> +    means no period is specified.
> +    Applicable to H264 and HEVC encoders.

I'm confused. Isn't this the same as V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB?
Except that here you don't give the number of macroblocks but instead the number
of frames it will take to fully refresh a frame and leave it to the driver to
calculate the number of macroblocks?

If I am right, then you need to clearly document the relationship between the
two controls, and what happens if you set them both.

It seems the venus driver already supports V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB,
so why add this control as well?

Regards,

	Hans

> +
>  ``V4L2_CID_MPEG_VIDEO_FRAME_RC_ENABLE (boolean)``
>      Frame level rate control enable. If this control is disabled then
>      the quantization parameter for each frame type is constant and set
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index 5cbe0ffbf501..ac44848d2d6e 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -869,6 +869,7 @@ const char *v4l2_ctrl_get_name(u32 id)
>  	case V4L2_CID_MPEG_VIDEO_DECODER_SLICE_INTERFACE:	return "Decoder Slice Interface";
>  	case V4L2_CID_MPEG_VIDEO_DECODER_MPEG4_DEBLOCK_FILTER:	return "MPEG4 Loop Filter Enable";
>  	case V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB:	return "Number of Intra Refresh MBs";
> +	case V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD:		return "Intra Refresh Period";
>  	case V4L2_CID_MPEG_VIDEO_FRAME_RC_ENABLE:		return "Frame Level Rate Control Enable";
>  	case V4L2_CID_MPEG_VIDEO_MB_RC_ENABLE:			return "H264 MB Level Rate Control";
>  	case V4L2_CID_MPEG_VIDEO_HEADER_MODE:			return "Sequence Header Mode";
> @@ -1260,6 +1261,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
>  		break;
>  	case V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE:
>  	case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:
> +	case V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD:
>  		*type = V4L2_CTRL_TYPE_INTEGER;
>  		break;
>  	case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME:
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 823b214aac0c..54b9072ac49d 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -422,6 +422,7 @@ enum v4l2_mpeg_video_multi_slice_mode {
>  #define V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE		(V4L2_CID_CODEC_BASE+227)
>  #define V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE		(V4L2_CID_CODEC_BASE+228)
>  #define V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME		(V4L2_CID_CODEC_BASE+229)
> +#define V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD	(V4L2_CID_CODEC_BASE+230)
>  
>  /* CIDs for the MPEG-2 Part 2 (H.262) codec */
>  #define V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL			(V4L2_CID_CODEC_BASE+270)
>