[x264-devel] x264 encoding corruption bug w/ AltiVec enabled

[Timothy Pearson]

On 01/31/2019 03:57 AM, Luca Barbato wrote:
>> To be 100% sure it is out of the picture could you please convert the
>> input to y4m and disable libavcodec and libavformat from your x264 build?
> 
> I tried locally and using a y4m source it shows no problem that I could
> see, are all the patches from https://github.com/lu-zero/x264/ folded in
> the tree you are using?
> 
> lu

After some interactive debugging, we've narrowed the corruption down to
two causes:

1.) The master x264 tree fails checkasm in the luma category

2.) Even when using a known good tree (passes checkasm8 and checkasm10),
encoding a yuv422 file (both input and output as yuv422) will produce a
file corrupted beyond recognition.  yuv420 does not have this problem.

Sample of corrupted output:

http://imgbin.ca/image.uploads/31-01-2019/original-7f7b0a742265bf05563c6ed4212928b0.png

Command line to generate:

x264 --threads 16 --fps 30 --keyint 30 --min-keyint 30 --scenecut 0
--preset ultrafast --tune grain --bitrate 25600 --output-csp i422
--trellis 0 -o Big_Buck_Bunny_encoding_failure.ogv Big_Buck_Bunny_yuv422.y4m

-- 
Timothy Pearson
Raptor Engineering
+1 (415) 727-8645 (direct line)
+1 (512) 690-0200 (switchboard)
https://www.raptorengineering.com