Re: [PATCH v1 1/4] media: v4l2-controls: Add control for background detection

[Nicolas Dufresne]

Le mardi 24 mars 2026 à 14:03 +0900, Jackson.lee a écrit :
> From: Jackson Lee <jackson.lee@xxxxxxxxxxxxxxx>
> 
> Add a generic V4L2 boolean control V4L2_CID_MPEG_VIDEO_BACKGROUND_DETECTION
> that allows encoders to detect background regions in a frame and use fewer
> bits or skip mode to encode them, potentially reducing bitrate for streams
> with stationary scenes.
> 
> Signed-off-by: Jackson Lee <jackson.lee@xxxxxxxxxxxxxxx>
> Signed-off-by: Nas Chung <nas.chung@xxxxxxxxxxxxxxx>

Reviewed-by: Nicolas Dufresne <nicolas.dufresne@xxxxxxxxxxxxx>

> ---
>  Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 6 ++++++
>  drivers/media/v4l2-core/v4l2-ctrls-defs.c                 | 2 ++
>  include/uapi/linux/v4l2-controls.h                        | 2 ++
>  3 files changed, 10 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index c8890cb5e00a..ab865a1a6ba9 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -737,6 +737,12 @@ enum v4l2_mpeg_video_frame_skip_mode -
>      Enable writing sample aspect ratio in the Video Usability
>      Information. Applicable to the H264 encoder.
>  
> +``V4L2_CID_MPEG_VIDEO_BACKGROUND_DETECTION (boolean)``
> +    If enabled, the encoder detect a background region in frame and
> +    use low bits or skip mode to encode the background region.
> +    If a lot of scenes are stationary or background, It may help to
> +    reduce the video bitrate. Applicable to the encoder.
> +
>  .. _v4l2-mpeg-video-h264-vui-sar-idc:
>  
>  ``V4L2_CID_MPEG_VIDEO_H264_VUI_SAR_IDC``
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-
> core/v4l2-ctrls-defs.c
> index 551426c4cd01..e062f2088490 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -889,6 +889,7 @@ const char *v4l2_ctrl_get_name(u32 id)
>  	case V4L2_CID_MPEG_VIDEO_DEC_DISPLAY_DELAY:		return
> "Display Delay";
>  	case V4L2_CID_MPEG_VIDEO_DEC_DISPLAY_DELAY_ENABLE:	return
> "Display Delay Enable";
>  	case V4L2_CID_MPEG_VIDEO_AU_DELIMITER:			return
> "Generate Access Unit Delimiters";
> +	case V4L2_CID_MPEG_VIDEO_BACKGROUND_DETECTION:		return
> "Background Detection";
>  	case V4L2_CID_MPEG_VIDEO_H263_I_FRAME_QP:		return "H263
> I-Frame QP Value";
>  	case V4L2_CID_MPEG_VIDEO_H263_P_FRAME_QP:		return "H263
> P-Frame QP Value";
>  	case V4L2_CID_MPEG_VIDEO_H263_B_FRAME_QP:		return "H263
> B-Frame QP Value";
> @@ -1296,6 +1297,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum
> v4l2_ctrl_type *type,
>  	case V4L2_CID_MPEG_VIDEO_MPEG4_QPEL:
>  	case V4L2_CID_MPEG_VIDEO_REPEAT_SEQ_HEADER:
>  	case V4L2_CID_MPEG_VIDEO_AU_DELIMITER:
> +	case V4L2_CID_MPEG_VIDEO_BACKGROUND_DETECTION:
>  	case V4L2_CID_WIDE_DYNAMIC_RANGE:
>  	case V4L2_CID_IMAGE_STABILIZATION:
>  	case V4L2_CID_RDS_RECEPTION:
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-
> controls.h
> index 68dd0c4e47b2..affec0ab4781 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -464,6 +464,8 @@ enum v4l2_mpeg_video_intra_refresh_period_type {
>  	V4L2_CID_MPEG_VIDEO_INTRA_REFRESH_PERIOD_TYPE_CYCLIC	= 1,
>  };
>  
> +#define V4L2_CID_MPEG_VIDEO_BACKGROUND_DETECTION	(V4L2_CID_CODEC_BASE
> + 238)
> +
>  /* CIDs for the MPEG-2 Part 2 (H.262) codec */
>  #define
> V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL			(V4L2_CID_CODEC_BASE+270)
>  enum v4l2_mpeg_video_mpeg2_level {

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