[FFmpeg-devel] [PATCH] Increase max_pic_num

[Michael Niedermayer]

Hi

On Tue, Oct 09, 2007 at 11:17:01AM -0400, Jeff Downs wrote:
> Hi,
> 
> On Tue, 9 Oct 2007, Carl Eugen Hoyos wrote:
> 
> > Hi!
> > 
> > After enabling PAFF decoding, for one sample (PREMIERE HD), I get these
> > errors together with heavy picture distortion:
> > 
> > [h264 @ 0x894cef0]abs_diff_pic_num overflow
> > [h264 @ 0x894cef0]decode_slice_header error
> > 
> > Attached patch fixes both the errors and the picture for this sample.
> > 
> 
> The distortion you receive is because the decoder drops those (reference) 
> frames when this error trips.
> 
> > Index: libavcodec/h264.c
> > ===================================================================
> > --- libavcodec/h264.c	(Revision 10695)
> > +++ libavcodec/h264.c	(Arbeitskopie)
> > @@ -4064,7 +4064,7 @@
> >          h->max_pic_num= 1<< h->sps.log2_max_frame_num;
> >      }else{
> >          h->curr_pic_num= 2*h->frame_num + 1;
> > -        h->max_pic_num= 1<<(h->sps.log2_max_frame_num + 1);
> > +        h->max_pic_num= (1<<(h->sps.log2_max_frame_num + 1)) + 1;
> >      }
> >  
> >      if(h->nal_unit_type == NAL_IDR_SLICE){
> 
> This will likely cause issues with reference picture management and list 
> building because max_pic_num will be wrong.
> 
> I think the actual problem (has been there since before paff) is in the 
> check that causes that error to post.  The spec says its perfectly 
> legitimate to have an abs_diff_pic_num == max_pic_num.
> 
> The following patch should fix this.

patch ok (if it fixes it)

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have often repented speaking, but never of holding my tongue.
-- Xenocrates
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