linux-kernel - Re: [PATCH v3 2/3] media: uapi: Add VP9 stateless decoder controls

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Date:   Mon, 11 May 2020 08:17:06 -0400
From:   Nicolas Dufresne <nicolas.dufresne@...labora.com>
To:     Hans Verkuil <hverkuil@...all.nl>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Cc:     Tomasz Figa <tfiga@...omium.org>, kernel@...labora.com,
        Jonas Karlman <jonas@...boo.se>,
        Heiko Stuebner <heiko@...ech.de>,
        Alexandre Courbot <acourbot@...omium.org>,
        Jeffrey Kardatzke <jkardatzke@...omium.org>,
        gustavo.padovan@...labora.com,
        Boris Brezillon <boris.brezillon@...labora.com>
Subject: Re: [PATCH v3 2/3] media: uapi: Add VP9 stateless decoder controls

Le vendredi 08 mai 2020 à 15:16 +0200, Hans Verkuil a écrit :
> > I think this comes directly from the spec. The Rockchip VDEC doesn't
> > seem to use it.
> > Do you think we can drop it from here, and rely on the V4L2 colorspace
> > passed in the format negotiation?
> 
> 
> That would be preferred, yes. Otherwise you would have two places where you can
> define colorspaces, and that's confusing.

This is indeed redundant with the color information in the format. In
VP8/9 there is only 1 header for everything, so it's harder to figure-
out what to filter. While in H.264/HEVC this information is usually set
an an extension header.

Though this do re-open the discussion about SPS in H.264/HEVC. In there
you will find the coded size and the crop window and the sub-sampling.
I don't remember exactly what was the conclusion, but I think it was
kept to allow allow bitstream reconstruction. But it will effectively
overlap directly (or indirectly) with some V4L2 generic API.

regards,
Nicolas

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