linux-kernel - Re: [PATCH v3 1/3] media: v4l2-ctrls: Add average qp control

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Date: Wed, 22 May 2024 13:38:02 +0200
From: Hans Verkuil <hverkuil-cisco@...all.nl>
To: Ming Qian <ming.qian@....com>, mchehab@...nel.org
Cc: nicolas@...fresne.ca, shawnguo@...nel.org, robh+dt@...nel.org,
 s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com,
 linux-imx@....com, xiahong.bao@....com, eagle.zhou@....com,
 tao.jiang_2@....com, ming.qian@....nxp.com, imx@...ts.linux.dev,
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 1/3] media: v4l2-ctrls: Add average qp control

On 06/05/2024 10:49, Ming Qian wrote:
> Add a control V4L2_CID_MPEG_VIDEO_AVERAGE_QP to report the average qp
> value of current encoded frame. the value applies to the last dequeued
> capture buffer.
> 
> Signed-off-by: Ming Qian <ming.qian@....com>

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

Regards,

	Hans

> ---
> v3
> - document the valid range of the new ctrl
> 
> v2
>  - improve document description according Hans's comments
>  - drop volatile flag
> 
>  .../userspace-api/media/v4l/ext-ctrls-codec.rst    | 14 ++++++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls-defs.c          |  5 +++++
>  include/uapi/linux/v4l2-controls.h                 |  2 ++
>  3 files changed, 21 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 2a165ae063fb..4a379bd9e3fb 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -1653,6 +1653,20 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_type -
>      Quantization parameter for a P frame for FWHT. Valid range: from 1
>      to 31.
>  
> +``V4L2_CID_MPEG_VIDEO_AVERAGE_QP (integer)``
> +    This read-only control returns the average QP value of the currently
> +    encoded frame. The value applies to the last dequeued capture buffer
> +    (VIDIOC_DQBUF). Its valid range depends on the encoding format and parameters.
> +    For H264, its valid range is from 0 to 51.
> +    For HEVC, its valid range is from 0 to 51 for 8 bit and
> +    from 0 to 63 for 10 bit.
> +    For H263 and MPEG4, its valid range is from 1 to 31.
> +    For VP8, its valid range is from 0 to 127.
> +    For VP9, its valid range is from 0 to 255.
> +    If the codec's MIN_QP and MAX_QP are set, then the QP will meet both requirements.
> +    Codecs need to always use the specified range, rather then a HW custom range.
> +    Applicable to encoders
> +
>  .. raw:: latex
>  
>      \normalsize
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> index 8696eb1cdd61..1ea52011247a 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> @@ -970,6 +970,7 @@ const char *v4l2_ctrl_get_name(u32 id)
>  	case V4L2_CID_MPEG_VIDEO_LTR_COUNT:			return "LTR Count";
>  	case V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX:		return "Frame LTR Index";
>  	case V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES:		return "Use LTR Frames";
> +	case V4L2_CID_MPEG_VIDEO_AVERAGE_QP:			return "Average QP Value";
>  	case V4L2_CID_FWHT_I_FRAME_QP:				return "FWHT I-Frame QP Value";
>  	case V4L2_CID_FWHT_P_FRAME_QP:				return "FWHT P-Frame QP Value";
>  
> @@ -1507,6 +1508,10 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
>  		*max = 0xffffffffffffLL;
>  		*step = 1;
>  		break;
> +	case V4L2_CID_MPEG_VIDEO_AVERAGE_QP:
> +		*type = V4L2_CTRL_TYPE_INTEGER;
> +		*flags |= V4L2_CTRL_FLAG_READ_ONLY;
> +		break;
>  	case V4L2_CID_PIXEL_RATE:
>  		*type = V4L2_CTRL_TYPE_INTEGER64;
>  		*flags |= V4L2_CTRL_FLAG_READ_ONLY;
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 99c3f5e99da7..974fd254e573 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -898,6 +898,8 @@ enum v4l2_mpeg_video_av1_level {
>  	V4L2_MPEG_VIDEO_AV1_LEVEL_7_3 = 23
>  };
>  
> +#define V4L2_CID_MPEG_VIDEO_AVERAGE_QP  (V4L2_CID_CODEC_BASE + 657)
> +
>  /*  MPEG-class control IDs specific to the CX2341x driver as defined by V4L2 */
>  #define V4L2_CID_CODEC_CX2341X_BASE				(V4L2_CTRL_CLASS_CODEC | 0x1000)
>  #define V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE		(V4L2_CID_CODEC_CX2341X_BASE+0)