media: v4l2-ctrl: Add control for h.264 chroma qp offset

Allow to add fixed quantization parameter offset between luma and
chroma quantization parameters. This control directly corresponds
to the chroma_qp_index_offset field of the h.264 picture parameter
set.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

Documentation/media/uapi/v4l/extended-controls.rst

@@ -1158,6 +1158,11 @@ enum v4l2_mpeg_video_h264_entropy_mode -
     Enable constrained intra prediction for H264. Applicable to the H264
     encoder.
 
+``V4L2_CID_MPEG_VIDEO_H264_CHROMA_QP_INDEX_OFFSET (integer)``
+    Specify the offset that should be added to the luma quantization
+    parameter to determine the chroma quantization parameter. Applicable
+    to the H264 encoder.
+
 ``V4L2_CID_MPEG_VIDEO_CYCLIC_INTRA_REFRESH_MB (integer)``
     Cyclic intra macroblock refresh. This is the number of continuous
     macroblocks refreshed every frame. Each frame a successive set of

drivers/media/v4l2-core/v4l2-ctrls.c

@@ -827,6 +827,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 								return "H264 Set QP Value for HC Layers";
 	case V4L2_CID_MPEG_VIDEO_H264_CONSTRAINED_INTRA_PREDICTION:
 								return "H264 Constrained Intra Pred";
+	case V4L2_CID_MPEG_VIDEO_H264_CHROMA_QP_INDEX_OFFSET:	return "H264 Chroma QP Index Offset";
 	case V4L2_CID_MPEG_VIDEO_MPEG4_I_FRAME_QP:		return "MPEG4 I-Frame QP Value";
 	case V4L2_CID_MPEG_VIDEO_MPEG4_P_FRAME_QP:		return "MPEG4 P-Frame QP Value";
 	case V4L2_CID_MPEG_VIDEO_MPEG4_B_FRAME_QP:		return "MPEG4 B-Frame QP Value";

include/uapi/linux/v4l2-controls.h

@@ -534,6 +534,7 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type {
 #define V4L2_CID_MPEG_VIDEO_H264_HIERARCHICAL_CODING_LAYER	(V4L2_CID_MPEG_BASE+381)
 #define V4L2_CID_MPEG_VIDEO_H264_HIERARCHICAL_CODING_LAYER_QP	(V4L2_CID_MPEG_BASE+382)
 #define V4L2_CID_MPEG_VIDEO_H264_CONSTRAINED_INTRA_PREDICTION	(V4L2_CID_MPEG_BASE+383)
+#define V4L2_CID_MPEG_VIDEO_H264_CHROMA_QP_INDEX_OFFSET		(V4L2_CID_MPEG_BASE+384)
 #define V4L2_CID_MPEG_VIDEO_MPEG4_I_FRAME_QP	(V4L2_CID_MPEG_BASE+400)
 #define V4L2_CID_MPEG_VIDEO_MPEG4_P_FRAME_QP	(V4L2_CID_MPEG_BASE+401)
 #define V4L2_CID_MPEG_VIDEO_MPEG4_B_FRAME_QP	(V4L2_CID_MPEG_BASE+402)