[FFmpeg-devel] [RFC] H.264 error concealment and mpegvideo frame handling

[Michael Niedermayer]

On Wed, Sep 22, 2010 at 01:29:35AM -0700, Jason Garrett-Glaser wrote:
> ffh264 does not handle the case of missing reference frames correctly.
>  Suppose we have 16 refs and we just decoded frame num 18.  Here's our
> reflist:
> 
> 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4
> 
> Then, we decode frame num 20 (19 went missing):
> 
> 4 18 17 16 15 14 13 12 11 10 9 8 7 6 5
> 
> This is obviously buggy and wrong.  So I do this to fix it:
> 
> --- libavcodec/h264.c	(revision 25148)
> +++ libavcodec/h264.c	(working copy)
> @@ -1905,6 +1905,8 @@
>              s->current_picture_ptr->frame_num= h->prev_frame_num;
>              ff_generate_sliding_window_mmcos(h);
>              ff_h264_execute_ref_pic_marking(h, h->mmco, h->mmco_index);
> +            ff_copy_picture(h->short_ref[0], h->short_ref[1]);
> +            h->short_ref[0]->frame_num = h->prev_frame_num;
>          }
> 
>          /* See if we have a decoded first field looking for a pair... */
> 
> This gives us:
> 
> 18 18 17 16 15 14 13 12 11 10 9 8 7 6 5

shouldnt that be 19 18 ... ?

either way ff_copy_picture() is wrong, we should for the entries that are
left after gap handling allocate seperate pictures and fill them (this
filling could then in the future be replaced by code that uses the b frame
direct mode and motion vectors of the surrounding frames)

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

Thouse who are best at talking, realize last or never when they are wrong.
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