[FFmpeg-devel] [PATCH 4/4] vc2enc: only warn on a non-standard base video format

Michael Niedermayer michael at niedermayer.cc
Thu Apr 21 04:54:11 CEST 2016

On Sun, Apr 17, 2016 at 06:53:58PM +0100, Rostislav Pehlivanov wrote:
> On 17 April 2016 at 03:40, Michael Niedermayer <michael at niedermayer.cc>
> wrote:
> >
> > is this a spec compliance or a profile compliance issue or something
> > else ?
> >
> > from just the Commit message above it sounds a bit like a profile /
> > hw decoder limitation, in which case this patch with a different
> > av_log() message should be ok ...
> >
> >
> It's a hardware limitation. Basically, SMPTE ST 2042-2:2009 (a separate
> specification from the VC-2 specs) defines levels 1-7, an each level has a
> few associated base video formats (e.g. 6 for 4K and 3 for 720/1080). So
> each hardware decoder which claims to support a level must support all
> video formats associated with that level. The VC-2 specifications say
> nothing about restricting the level. Our decoder doesn't care about the
> level since Dirac was a general purpose codec and so it supports everything.
> BTW the encoder hasn't been tested on hardware, and I've only heard of
> legends about such existing. The spec isn't well written so I'm pretty sure
> turning on huge slice sizes would crash hardware decoders since they'd have
> no memory. So the level value doesn't do much at all to ensure hardware can
> still decode.

then patch LGTM


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Frequently ignored answer#1 FFmpeg bugs should be sent to our bugtracker. User
questions about the command line tools should be sent to the ffmpeg-user ML.
And questions about how to use libav* should be sent to the libav-user ML.
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