[FFmpeg-devel] [RFC] Error concealment for B-frames/fixing issue 824

Baptiste Coudurier baptiste.coudurier
Mon Apr 13 01:07:57 CEST 2009

On Fri, Apr 10, 2009 at 06:50:08PM -0700, Baptiste Coudurier wrote:
> Hi Reimar,
> On 4/9/2009 3:13 PM, Reimar D?ffinger wrote:
> > On Thu, Apr 09, 2009 at 10:52:32PM +0200, Michael Niedermayer wrote:
> >> there are 2 very seperate things
> >> 1. errors
> >> 2. b frames without reference frames after seeking
> >>
> >> normal users dont want to see randomly trashed frames after seeking
> >> in undamged files
> > 
> > I think I agree... Is there a counter somewhere that could be used to
> > find out which frame in the GOP we are at?
> Yes temp_ref in pic structure.
> > Some options I can think of:
> > 1) change code to not skip a B-frame if it is the second frame in a closed GOP
> > 2) only skip B-frames if they directly follow the first I-frame of a non-closed GOP
> > 3) (without really knowing what "broken link" means) only skip B-frames if "broken
> > link" is set
> From what I understand, broken link explicitly state that the 2 next b
> frames cannot be decoded because the stream was cut at the preceding I
> frame, therefore the original reference I frame is no more available.
> And I think your strategy should be ok :)

Here is another attempt.

It will decodes them only is closed gop is set.
I got a sample with open gop and B frames before the I frame, it
works, also, decoding them anyway does not crash when dummy picture is
allocated some block are gray.

Patch attached.

Baptiste COUDURIER                              GnuPG Key Id: 0x5C1ABAAA    
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FFmpeg maintainer                                  http://www.ffmpeg.org
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