linux-kernel - Re: [PATCH v2 1/4] media: v4l2-ctrls: Add encoder constant quality control

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Message-ID: <075e4109-00ed-4c47-009a-84915ed6f75a@xs4all.nl>
Date:   Mon, 20 Jul 2020 11:06:15 +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>,
        Maheshwar Ajja <majja@...eaurora.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH v2 1/4] media: v4l2-ctrls: Add encoder constant quality
 control

On 16/06/2020 22:14, Stanimir Varbanov wrote:
> From: Maheshwar Ajja <majja@...eaurora.org>
> 
> 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@...eaurora.org>
> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>

Reviewed-by: Hans Verkuil <hverkuil-cisco@...all.nl>

Thanks!

	Hans

> ---
>  .../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 d0d506a444b1..b9d3f7ae6486 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 3f3fbcd60cc6..bc00d02e411f 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -200,6 +200,7 @@ 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[] = {
> @@ -832,6 +833,7 @@ const char *v4l2_ctrl_get_name(u32 id)
>  	case V4L2_CID_MPEG_VIDEO_GOP_CLOSURE:	return "Video GOP Closure";
>  	case V4L2_CID_MPEG_VIDEO_PULLDOWN:	return "Video Pulldown";
>  	case V4L2_CID_MPEG_VIDEO_BITRATE_MODE:	return "Video Bitrate Mode";
> +	case V4L2_CID_MPEG_VIDEO_CONSTANT_QUALITY:	return "Constant Quality";
>  	case V4L2_CID_MPEG_VIDEO_BITRATE:	return "Video Bitrate";
>  	case V4L2_CID_MPEG_VIDEO_BITRATE_PEAK:	return "Video Peak Bitrate";
>  	case V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION: return "Video Temporal Decimation";
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 62271418c1be..0f7e4388dcce 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)
>