linux-kernel - Re: [PATCH 40/40] media: imx: set and propagate empty field, colorimetry params

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Date:   Tue, 18 Apr 2017 11:30:19 +0200
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Steve Longerbeam <slongerbeam@...il.com>
Cc:     gregkh@...uxfoundation.org, mchehab@...nel.org,
        rmk+kernel@...linux.org.uk, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        Steve Longerbeam <steve_longerbeam@...tor.com>
Subject: Re: [PATCH 40/40] media: imx: set and propagate empty field,
 colorimetry params

On Thu, 2017-04-13 at 09:40 -0700, Steve Longerbeam wrote:
[...]
> >> @@ -804,12 +804,29 @@ static void prp_try_fmt(struct prp_priv *priv,
> >>  					      &sdformat->format.height,
> >>  					      infmt->height / 4, MAX_H_SRC,
> >>  					      H_ALIGN_SRC, S_ALIGN);
> >> +
> >> +		/*
> >> +		 * The Image Converter produces fixed quantization
> >> +		 * (full range for RGB, limited range for YUV), and
> >> +		 * uses a fixed Y`CbCr encoding (V4L2_YCBCR_ENC_601).
> >> +		 * For colorspace and transfer func, just propagate
> >> +		 * from the sink.
> >> +		 */
> >> +		sdformat->format.quantization =
> >> +			((*cc)->cs != IPUV3_COLORSPACE_YUV) ?
> >> +			V4L2_QUANTIZATION_FULL_RANGE :
> >> +			V4L2_QUANTIZATION_LIM_RANGE;
> >> +		sdformat->format.ycbcr_enc = V4L2_YCBCR_ENC_601;
> >
> > Support for V4L2_YCBCR_ENC_709 and quantization options could be added
> > to the IPUv3 core code, so this limitation could be relaxed later.
> 
> Yes, I was going to mention that too. We can add coefficient tables
> to ipu-ic for all the encodings enumerated in enum v4l2_ycbcr_encoding.

Exactly.

> I know that quantization is programmable in the DP, but is it in the
> IC? AFAICT there is none.

We have a freely programmable 4x3 matrix multiplication both before and
after processing in each task, and there is a saturation mode switch
that can limit the first component to (16...235) and the other two to
(16...240). That should be enough for at least full/limited range YCbCr
quantizations. So we apparently can't saturate to limited range RGB, but
for example full-range -> limited-range RGB conversions should be
perfectly possible.

regards
Philipp