From: Jackson Lee <jackson.lee@chipsnmedia.com>

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@chipsnmedia.com>
Signed-off-by: Nas Chung <nas.chung@chipsnmedia.com>
---
 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 {
-- 
2.43.0