linux-kernel - Re: [EXT] Re: [PATCH v4 00/11] Add V4L2 driver for i.MX8 JPEG Encoder/Decoder

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Date:   Fri, 6 Nov 2020 01:04:45 +0000
From:   Mirela Rabulea <mirela.rabulea@....com>
To:     "mchehab@...nel.org" <mchehab@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "Mirela Rabulea (OSS)" <mirela.rabulea@....nxp.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>
CC:     dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "laurent.pinchart+renesas@...asonboard.com" 
        <laurent.pinchart+renesas@...asonboard.com>,
        Aisheng Dong <aisheng.dong@....com>,
        Laurentiu Palcu <laurentiu.palcu@....com>,
        Robert Chiras <robert.chiras@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
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        "p.zabel@...gutronix.de" <p.zabel@...gutronix.de>,
        "niklas.soderlund+renesas@...natech.se" 
        <niklas.soderlund+renesas@...natech.se>,
        Daniel Baluta <daniel.baluta@....com>,
        "dafna.hirschfeld@...labora.com" <dafna.hirschfeld@...labora.com>,
        "ezequiel@...labora.com" <ezequiel@...labora.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
Subject: Re: [EXT] Re: [PATCH v4 00/11] Add V4L2 driver for i.MX8 JPEG
 Encoder/Decoder

On Wed, 2020-11-04 at 15:08 +0100, Hans Verkuil wrote:
> 
> This was never really well defined. Basically the JPEG standard
> doesn't
> store colorimetry as metadata, instead it is understood to be sRGB
> colorimetry.
> 
> So if you take what a HW JPEG encoder creates and want to show it on
> another
> device, then it will be interpreted as sRGB. Now if userspace adds
> some JPEG
> extension where it declares the colorimetry to be something else,
> then that
> is fine, but that's out of scope of a HW JPEG encoder driver, IMHO.
> 
> I suspect that the coda patch was actually trying to make coda behave
> with
> an older version of v4l2-compliance where a JPEG codec was tested in
> the
> same way as a H264 codec. Later we realized that that didn't make
> sense for
> JPEG codecs and the test was changed. But now coda fails on that
> test.
> 
> > Once I clarify on this, I'll include a fix in v5.
> 
> I hope this helps.
> 
>         Hans
> 

Thanks for clarifying, I fixed the colorspace information to sRGB, for
both capture & output (V4L2_COLORSPACE_SRGB, V4L2_YCBCR_ENC_601 and
V4L2_QUANTIZATION_FULL_RANGE). All pass now. It will be in the next
version.