[FFmpeg-devel] [PATCH] Add coded_width/height to AVCodecParameters

Michael Niedermayer michael at niedermayer.cc
Sun Apr 3 15:26:02 CEST 2016

On Sun, Apr 03, 2016 at 02:31:06PM +0200, Hendrik Leppkes wrote:
> On Sun, Apr 3, 2016 at 2:07 PM, Michael Niedermayer
> <michael at niedermayer.cc> wrote:
> > Without this or some other change moving data back and forth corrupts it
> > as the cropped & possibly low res resolution modified w/h will be taken
> > a the pre lowres resolution
> > also without 2 sets theres no place to communicate the cropped dimensions
> >
> > can be reproduced with
> > ./ffplay_g -vlowres 2 tickets/162/avid.avi
> >
> lowres is supposed to be applied in the decoder, not the demuxer, so I
> don't see how this is required here.

if iam not mistaken (please correct me if iam wrong)

the demuxer runs a decoder, which initializes various AVCodecContext
fields these then get copied into AVCodecParameters and back into
the users AVCodecContext used for the user appliations decoder

the first decoder will set width & height to the low resolution
with lowres, coded_width / height will represent the stored, true
the data copied into the AVCodecParameters will have lost the width
& height that is stored anywhere but rather contain the lowres

the user app then will initialize its decoder based on coded_width
and coded_height which it will find set to 0 so it fallback to the
compatibility hack of using width & height which are the lowres
values and the decoder will apply the lowres stuff again

above is based on some assumtations i have not verified very step with
a debugger

> AVCodecParameters is supposed to contain container information, not
> pre-interpreted info based on some decoding options.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Never trust a computer, one day, it may think you are the virus. -- Compn
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