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Message-ID: <46ea74867fee6f0dbefb4c2d24a682d15beb41e7.camel@ndufresne.ca>
Subject: Re: [PATCH 1/2] media: v4l2-ctrls: Add average qp control
From: Nicolas Dufresne <nicolas@ndufresne.ca>
To: Hans Verkuil <hverkuil-cisco@xs4all.nl>, Ming Qian <ming.qian@nxp.com>, 
	mchehab@kernel.org
Cc: shawnguo@kernel.org, robh+dt@kernel.org, s.hauer@pengutronix.de, 
 kernel@pengutronix.de, festevam@gmail.com, linux-imx@nxp.com,
 xiahong.bao@nxp.com,  eagle.zhou@nxp.com, tao.jiang_2@nxp.com,
 ming.qian@oss.nxp.com,  imx@lists.linux.dev, linux-media@vger.kernel.org,
 linux-kernel@vger.kernel.org,  linux-arm-kernel@lists.infradead.org
Date: Wed, 01 May 2024 15:55:46 -0400
In-Reply-To: <25a33db9-3bc1-4d90-83d4-0bdbea9bc5d8@xs4all.nl>
References: <20240329092352.2648837-1-ming.qian@nxp.com>
	 <25a33db9-3bc1-4d90-83d4-0bdbea9bc5d8@xs4all.nl>
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Le mercredi 24 avril 2024 =C3=A0 12:03 +0200, Hans Verkuil a =C3=A9crit=C2=
=A0:
> On 29/03/2024 10:23, Ming Qian wrote:
> > Add a control V4L2_CID_MPEG_VIDEO_AVERAGE_QP to report the average qp
> > value of current encoded frame.
> >=20
> > Signed-off-by: Ming Qian <ming.qian@nxp.com>
> > ---
> >  Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst | 4 ++++
> >  drivers/media/v4l2-core/v4l2-ctrls-defs.c                 | 5 +++++
> >  include/uapi/linux/v4l2-controls.h                        | 2 ++
> >  3 files changed, 11 insertions(+)
> >=20
> > diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst =
b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > index 2a165ae063fb..cef20b3f54ca 100644
> > --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> > @@ -1653,6 +1653,10 @@ enum v4l2_mpeg_video_h264_hierarchical_coding_ty=
pe -
> >      Quantization parameter for a P frame for FWHT. Valid range: from 1
> >      to 31.
> > =20
> > +``V4L2_CID_MPEG_VIDEO_AVERAGE_QP (integer)``
> > +    This read-only control returns the average qp value of the current=
ly
> > +    encoded frame. Applicable to the H264 and HEVC encoders.
>=20
> qp -> QP
>=20
> Why is this applicable to H264/HEVC only? I think it is fine for any code=
c.

Same question, though we should document the range, which will differ per-
codecs. We should also document to always use the specified range, rather t=
hen a
HW custom range. This way we don't endup with issues we have hit with other=
 ill-
defined controls.

Nicolas

>=20
> This needs to document that the value applies to the last dequeued buffer
> (VIDIOC_DQBUF).
>=20
> > +
> >  .. raw:: latex
> > =20
> >      \normalsize
> > diff --git a/drivers/media/v4l2-core/v4l2-ctrls-defs.c b/drivers/media/=
v4l2-core/v4l2-ctrls-defs.c
> > index 8696eb1cdd61..88e86e4e539d 100644
> > --- a/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > +++ b/drivers/media/v4l2-core/v4l2-ctrls-defs.c
> > @@ -972,6 +972,7 @@ const char *v4l2_ctrl_get_name(u32 id)
> >  	case V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES:		return "Use LTR Frames";
> >  	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";
> > +	case V4L2_CID_MPEG_VIDEO_AVERAGE_QP:			return "Average QP value";
>=20
> value -> Value
>=20
> Also move it up two lines so that it follows V4L2_CID_MPEG_VIDEO_USE_LTR_=
FRAMES
> rather than FWHT controls.
>=20
> > =20
> >  	/* VPX controls */
> >  	case V4L2_CID_MPEG_VIDEO_VPX_NUM_PARTITIONS:		return "VPX Number of P=
artitions";
> > @@ -1507,6 +1508,10 @@ void v4l2_ctrl_fill(u32 id, const char **name, e=
num v4l2_ctrl_type *type,
> >  		*max =3D 0xffffffffffffLL;
> >  		*step =3D 1;
> >  		break;
> > +	case V4L2_CID_MPEG_VIDEO_AVERAGE_QP:
> > +		*type =3D V4L2_CTRL_TYPE_INTEGER;
> > +		*flags |=3D V4L2_CTRL_FLAG_VOLATILE | V4L2_CTRL_FLAG_READ_ONLY;
>=20
> Drop the volatile flag, this isn't a volatile value.
>=20
> > +		break;
> >  	case V4L2_CID_PIXEL_RATE:
> >  		*type =3D V4L2_CTRL_TYPE_INTEGER64;
> >  		*flags |=3D V4L2_CTRL_FLAG_READ_ONLY;
> > diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4=
l2-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 =3D 23
> >  };
> > =20
> > +#define V4L2_CID_MPEG_VIDEO_AVERAGE_QP  (V4L2_CID_CODEC_BASE + 657)
> > +
> >  /*  MPEG-class control IDs specific to the CX2341x driver as defined b=
y V4L2 */
> >  #define V4L2_CID_CODEC_CX2341X_BASE				(V4L2_CTRL_CLASS_CODEC | 0x1000=
)
> >  #define V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE		(V4L2_CID_COD=
EC_CX2341X_BASE+0)
>=20
> Regards,
>=20
> 	Hans
>=20