linux-kernel - Re: [PATCH 03/12] media: hantro: Fix H264 motion vector buffer offset

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Date:   Tue, 10 Sep 2019 11:18:34 +0100
From:   Ezequiel Garcia <ezequiel@...labora.com>
To:     Jonas Karlman <jonas@...boo.se>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-rockchip@...ts.infradead.org" 
        <linux-rockchip@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 03/12] media: hantro: Fix H264 motion vector buffer
 offset

Hi Jonas,

Thanks for fixing this, I'm happy we are reducing the amount
of black magic here.

On Sun, 2019-09-01 at 12:45 +0000, Jonas Karlman wrote:
> A decoded 8-bit 4:2:0 frame need memory for up to 448 macroblocks
> and is laid out in memory as follow:
> 
> +-------------------+
> > Y-plane   256 MBs |
> +-------------------+
> > UV-plane  128 MBs |
> +-------------------+
> > MV buffer  64 MBs |
> +-------------------+
> 
> The motion vector buffer offset is currently correct for 4:2:0 because
> the extra space for motion vectors is overallocated with an extra 64 MBs.
> 
> Wrong offset for both destination and motion vector buffer are used
> for the bottom field of field encoded content, wrong offset is
> also used for 4:0:0 (monochrome) content.
> 
> Fix this by always setting the motion vector address to the expected
> 384 MBs offset for 4:2:0 and 256 MBs offset for 4:0:0 content.
> 
> Also use correct destination and motion vector buffer offset
> for the bottom field of field encoded content.
> 
> While at it also extend the check for 4:0:0 (monochrome) to include an
> additional check for High Profile (100).
> 

As with the scaling list, I believe it would make a lot of sense
to document this in the driver itself.

Thanks,
Ezequiel