[x264-devel] CAVLC encoding broken at high resolutions

[BugMaster]

On Wed, 15 Sep 2010 15:04:53 +0200, Martin Fiedler wrote:
> Hi,

> while trying to encode video at very high resolutions (quad HD in my 
> case), I noticed that x264 generates broken H.264 streams when using 
> CAVLC instead of CABAC.

> Here is an example input video stream (~25 MB, 100 frames, 3840x2160, 
> losslessly compressed using FFV1) that exhibits the problem:
>      http://www.parhelic.de/~keyj/x264_broken_cavlc_example.avi
> when encoded using
>      x264 --no-cabac -o blah.264 x264_broken_cavlc_example.avi
> the resulting file shows visible artifacts. If --no-cabac is omitted, 
> the output is just fine.

> I found out that this bug has been introduced in r1327 87de234 and is 
> present until today (r1713 c276662). Since r1327 introduced weighted 
> P-frame prediction, I expected --weightp 0 to work around the bug, but
> this is only true for r1327. In the current revision, --weightp 0 
> actually makes it worse.

> I could not reproduce the bug with low resolutions (like 1920x1080) or
> with CABAC. Adding --no-mbtree also does not improve the situation.

> I hope that this report is helpful :)

> Best regards,

> Martin Fiedler
> _______________________________________________
> x264-devel mailing list
> x264-devel at videolan.org
> http://mailman.videolan.org/listinfo/x264-devel

Hi. It seems this is decoder bug. Both ffh264 and CoreAVC decodes it
with artefacts. But JM, MainConcept and Elecard decode it correctly.