[PATCH] media: v4l2-ctrls: Add encoder constant quality control

[Maheshwar Ajja]

When V4L2_CID_MPEG_VIDEO_BITRATE_MODE value is
V4L2_MPEG_VIDEO_BITRATE_MODE_CQ, encoder will produce
constant quality output indicated by
V4L2_CID_MPEG_VIDEO_CONSTANT_QUALITY control value.
Encoder will choose appropriate quantization parameter
and bitrate to produce requested frame quality level.

Signed-off-by: Maheshwar Ajja <majja@xxxxxxxxxxxxxx>
---
 Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 10 ++++++++++
 drivers/media/v4l2-core/v4l2-ctrls.c                      |  2 ++
 include/uapi/linux/v4l2-controls.h                        |  2 ++
 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 d0d506a..b9d3f7a 100644
--- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
+++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
@@ -581,6 +581,8 @@ enum v4l2_mpeg_video_bitrate_mode -
       - Variable bitrate
     * - ``V4L2_MPEG_VIDEO_BITRATE_MODE_CBR``
       - Constant bitrate
+    * - ``V4L2_MPEG_VIDEO_BITRATE_MODE_CQ``
+      - Constant quality
 
 
 
@@ -592,6 +594,14 @@ enum v4l2_mpeg_video_bitrate_mode -
     the average video bitrate. It is ignored if the video bitrate mode
     is set to constant bitrate.
 
+``V4L2_CID_MPEG_VIDEO_CONSTANT_QUALITY (integer)``
+    Constant quality level control. This control is applicable when
+    ``V4L2_CID_MPEG_VIDEO_BITRATE_MODE`` value is
+    ``V4L2_MPEG_VIDEO_BITRATE_MODE_CQ``. Valid range is 1 to 100
+    where 1 indicates lowest quality and 100 indicates highest quality.
+    Encoder will decide the appropriate quantization parameter and
+    bitrate to produce requested frame quality.
+
 ``V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION (integer)``
     For every captured frame, skip this many subsequent frames (default
     0).
diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
index 1c617b4..f94cc9d 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls.c
@@ -199,6 +199,7 @@ const char * const *v4l2_ctrl_get_menu(u32 id)
 	static const char * const mpeg_video_bitrate_mode[] = {
 		"Variable Bitrate",
 		"Constant Bitrate",
+		"Constant Quality",
 		NULL
 	};
 	static const char * const mpeg_stream_type[] = {
@@ -982,6 +983,7 @@ const char *v4l2_ctrl_get_name(u32 id)
 	case V4L2_CID_MPEG_VIDEO_HEVC_SLICE_PARAMS:		return "HEVC Slice Parameters";
 	case V4L2_CID_MPEG_VIDEO_HEVC_DECODE_MODE:		return "HEVC Decode Mode";
 	case V4L2_CID_MPEG_VIDEO_HEVC_START_CODE:		return "HEVC Start Code";
+	case V4L2_CID_MPEG_VIDEO_CONSTANT_QUALITY:		return "Constant Quality";
 
 	/* CAMERA controls */
 	/* Keep the order of the 'case's the same as in v4l2-controls.h! */
diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
index 0ba1005..ca916da 100644
--- a/include/uapi/linux/v4l2-controls.h
+++ b/include/uapi/linux/v4l2-controls.h
@@ -375,6 +375,7 @@ enum v4l2_mpeg_video_aspect {
 enum v4l2_mpeg_video_bitrate_mode {
 	V4L2_MPEG_VIDEO_BITRATE_MODE_VBR = 0,
 	V4L2_MPEG_VIDEO_BITRATE_MODE_CBR = 1,
+	V4L2_MPEG_VIDEO_BITRATE_MODE_CQ  = 2,
 };
 #define V4L2_CID_MPEG_VIDEO_BITRATE		(V4L2_CID_MPEG_BASE+207)
 #define V4L2_CID_MPEG_VIDEO_BITRATE_PEAK	(V4L2_CID_MPEG_BASE+208)
@@ -742,6 +743,7 @@ enum v4l2_cid_mpeg_video_hevc_size_of_length_field {
 #define V4L2_CID_MPEG_VIDEO_HEVC_HIER_CODING_L6_BR	(V4L2_CID_MPEG_BASE + 642)
 #define V4L2_CID_MPEG_VIDEO_REF_NUMBER_FOR_PFRAMES	(V4L2_CID_MPEG_BASE + 643)
 #define V4L2_CID_MPEG_VIDEO_PREPEND_SPSPPS_TO_IDR	(V4L2_CID_MPEG_BASE + 644)
+#define V4L2_CID_MPEG_VIDEO_CONSTANT_QUALITY		(V4L2_CID_MPEG_BASE + 645)
 
 /*  MPEG-class control IDs specific to the CX2341x driver as defined by V4L2 */
 #define V4L2_CID_MPEG_CX2341X_BASE				(V4L2_CTRL_CLASS_MPEG | 0x1000)
-- 
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