[FFmpeg-devel] Corrupted blocks and seeking issues in H264 disc sources

[Andreas Öman]

Hello,

infernix wrote:
> Hi,
> 
> Andreas, perhaps this new sample can give you more insight as to what 
> the problem is? If I find more blocks, I'll upload them and post a followup.
> 

I've taken a quick look at it, and it seems the motion vectors
are somehow incorrect for the affected macro blocks. see [1]
and [2]. (Both frames have errors in the bottom left part of
the picture)

I've done some additional tracing on [1]:

[h264 @ 0x84b1de8]pic:11 mb:15/58
[h264 @ 0x84b1de8]mb_type = 0x1008, partition_count = 1, cbp = 0x0
[h264 @ 0x84b1de8]pred_motion match_count=3
[h264 @ 0x84b1de8]pred_motion ( 0  0 -2) ( 0  0  0) ( 0  8 -8) -> ( 0  0 
-2) at 15 58 0 list 0
[h264 @ 0x84b1de8]final mv:198 102, cabac delta: 198 104

It would seem that the output from decode_cabac_mb_mvd() is
incorrect, but why (or if) it fails for this particular macroblock,
i'm not expert enough to tell.

[1] http://www.olebyn.nu/ffmpeg/issue4_mv_0076.png
[2] http://www.olebyn.nu/ffmpeg/issue5_mv_0050.png