linux-kernel - Re: [PATCH v3 1/2] media: v4l2-ctrls: Add intra-refresh period control

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Message-ID: <704d2df0-16dc-c1d6-d989-0ac176502cac@xs4all.nl>
Date:   Tue, 13 Apr 2021 17:56:27 +0200
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@...labora.com
Subject: Re: [PATCH v3 1/2] media: v4l2-ctrls: Add intra-refresh period
 control

On 02/03/2021 10:53, 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      | 12 ++++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls.c                 |  2 ++
>  include/uapi/linux/v4l2-controls.h                   |  1 +
>  3 files changed, 15 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 00944e97d638..49e6d364ded7 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -1104,6 +1104,18 @@ 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. In other words, this defines the number of frames
> +    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. Note that intra-refresh  is mutually

Double space after 'intra-refresh'

> +    exclusive with V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB control.

1) The same must be mentioned in the V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB
   control documentation as well.
2) What does it mean: 'mutually exclusive'? Does that mean that a driver
   implements only one or the other? If not, and both can be implemented, then
   how does userspace know which control is applied?

Also, you mentioned that V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB is
enumerated in the venus driver, but doesn't do anything. Wouldn't it be
better to remove it?

Regards,

	Hans

> +    Applicable to H264 and HEVC encoders.
> +
>  ``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 016cf6204cbb..2ee463e08f1e 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";
> @@ -1276,6 +1277,7 @@ 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 039c0d7add1b..1fddd9f0d4f1 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -428,6 +428,7 @@ enum v4l2_mpeg_video_multi_slice_mode {
>  #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_BASELAYER_PRIORITY_ID	(V4L2_CID_CODEC_BASE+230)
> +#define V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD	(V4L2_CID_CODEC_BASE+231)
>  
>  /* CIDs for the MPEG-2 Part 2 (H.262) codec */
>  #define V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL			(V4L2_CID_CODEC_BASE+270)
>