h264 - gray chroma - error while decoding - left block unavailable

[latot]

Hi all, well i found this problem from mpv, i can't reproduce a video, but when i test the file with ffmpeg don't works either.

This don't happen always, the version 3.2.6 is the last can reproduce and work with this video, but from 3.2.7 to 3.3.4 fails.

here a fragmente from:

ffmpeg -i in.mkv out.mkv

....
[h264 @ 0xa44ae0] Reference 6 >= 3
[h264 @ 0xa44ae0] error while decoding MB 39 2, bytestream 24332
[h264 @ 0xa44ae0] concealing 7930 DC, 7930 AC, 7930 MV errors in P frame
[h264 @ 0xa31460] top block unavailable for requested intra mode
[h264 @ 0xa31460] error while decoding MB 109 0, bytestream 20972
[h264 @ 0xa31460] concealing 8100 DC, 8100 AC, 8100 MV errors in P frame
[h264 @ 0x9dd5e0] Reference 4 >= 4
[h264 @ 0x9dd5e0] error while decoding MB 32 1, bytestream 22037
[h264 @ 0x9dd5e0] concealing 8057 DC, 8057 AC, 8057 MV errors in P frame
[h264 @ 0x9f26c0] gray chroma
[h264 @ 0x9f26c0] error while decoding MB 101 1, bytestream 24052
[h264 @ 0x9f26c0] concealing 7988 DC, 7988 AC, 7988 MV errors in P frame
[h264 @ 0x1c314c0] top block unavailable for requested intra mode
[h264 @ 0x1c314c0] error while decoding MB 106 0, bytestream 23977
[h264 @ 0x837e60] concealing 7769 DC, 7769 AC, 7769 MV errors in P frame
[h264 @ 0x1c314c0] concealing 8103 DC, 8103 AC, 8103 MV errors in P frame
[h264 @ 0xa56780] gray chroma
[h264 @ 0xa56780] error while decoding MB 84 0, bytestream 22106
[h264 @ 0xa56780] concealing 8125 DC, 8125 AC, 8125 MV errors in P frame
[h264 @ 0x1b488a0] concealing 7779 DC, 7779 AC, 7779 MV errors in P frame
[h264 @ 0xb65f60] gray chroma
[h264 @ 0xb65f60] error while decoding MB 17 2, bytestream 17086
[h264 @ 0xb65f60] concealing 7952 DC, 7952 AC, 7952 MV errors in P frame
frame= 47 fps= 45 q=0.0 size= 0kB time=00:00:01.63 bitrate= 0.0kbits/s[h264 @ 0xa44ae0] left block unavailable for requested intra mode
[h264 @ 0xa44ae0] error while decoding MB 0 2, bytestream 19416
[h264 @ 0xa44ae0] concealing 7969 DC, 7969 AC, 7969 MV errors in P frame
[h264 @ 0xa31460] gray chroma
[h264 @ 0xa31460] error while decoding MB 43 1, bytestream 19356
...

X10000000, and continue, and continue.

I found some things, first, i can reproduce this with ffmpeg-3.2.6 installed, all works, with upper version fails.

But, if i rencode the video with ffmpeg-3.2.6 the video start working with any version of ffmpeg.

I use Gentoo 64, and i try a lot of combinations of USEs but i get the same result.

Thx.

[latot]

test

[BugMaster]

This file is out of spec 4:4:4 x264 encode with x264 SEI removed (may be due splitting of mkv). It can't be decoded without x264 SEI. To fix it you need to either restore x264 SEI (with core 150 or lower) or re-encode it with new x264 version (r2851 core 151 or higher) where out of spec behavior was fixed (or with old version but 8x8dct disabled).

[latot]

D:

So the problem is in the file, and a mix with x264 if i understand right....

I upload only 5 segs of the file because is too big, but both have the same issue.

I don't have problem installing a lower core than 150 (i would like avoid rencoding), sadly i don't know how restore the SEI, can you help me please?, maybe with some doc, or place where i can found how do that? (i don't know how use ffmpeg for that)

Thx for your help.

[BugMaster]

I am dunno how to do this with ffmpeg itself but you can:
1) extract raw h264 video track from your mkv file
2) concat sei.h264 + video_track.h264 files to resulting fixed.h264
3) mux new fixed.mkv file which should decode correctly with all versions of ffmpeg

[latot]

Hi, sorry my ignorant question, but how i get the sei.h264?

and for concat you mean 'cat sei.h264 video_track.h264 > newfile'?

Thx.

[BugMaster]

I have attached sei.h264 above my previous comment. As for concat command, yes if you are at linux (on windows it can treate as text instead of binary and add not needed line breaks bytes). On windows it would be something like copy /B sei.h264 + video_track.h264 newfile.h264

[latot]

Hi, just finishing this (then, or now, i'll try fix all the filies i have with this), this sei.h264 file works for all the files with this problem?, or there is some condition or something?

Thx.

[BugMaster]

It should work for all the files with this problem where x264 detection (core 150) is needed.

[latot]

Hi!

I use this to fix 24 files, and now all seems to work!, thx for your solution.

Note, this solution is better than seems, because i'm using x264 with core 152 and now all the videos can be reproduced.

Thx.

[Carl Eugen Hoyos]

Can you explain how exactly you produced the broken files?

[latot]

Sadly no, i not produce this file, the only thing i know about this video is with one versions works and in the next not...

The closer issue i found with this is
​https://github.com/mpv-player/mpv/issues/4559

Where explain is possible a problem with a lower version of x264.

Thx.

[Thirumalaisamy K]

Replying to cehoyos:

Can you explain how exactly you produced the broken files?

Just encode a video with ffmpeg that's build with old x264 versions.
As of now all latest ffmpeg builds (both stable & git) at ​https://evermeet.cx/ffmpeg/ has issues.

you can just reproduce a similar file with the following command

ffmpeg -i input.ext -c:v libx264 -profile high444 -pix_fmt yuv444p -an out.ext

[Carl Eugen Hoyos]

Replying to KTSamy:

Replying to cehoyos:

Can you explain how exactly you produced the broken files?

Just encode a video with ffmpeg that's build with old x264 versions.
As of now all latest ffmpeg builds (both stable & git) at ​https://evermeet.cx/ffmpeg/ has issues.

you can just reproduce a similar file with the following command

ffmpeg -i input.ext -c:v libx264 -profile high444 -pix_fmt yuv444p -an out.ext

(This command line does not work.)
Did you test this yourself or are you speculating - the reason I ask is that so far, nobody could explain how to produce such a file: Don't you agree that it most likely isn't so easy?

[Terran Vigil]

Also ran into this, simply by decoding any source to yuv444, encoding that with x264 as high444. Decode the resulting mp4 with ffmpeg and you'll see the same issue as noted in this ticket. It appears to be a regression that was introduced in:

840b41b2a643fc8f0617c0370125a19c02c6b586

[Carl Eugen Hoyos]

Please explain how - exactly! - I can produce such a file.

[Thirumalaisamy K]

Replying to cehoyos:

Please explain how - exactly! - I can produce such a file.

I don't have exact issues with ffmpeg. But, with ffplay.

The method I have mentioned can produce the file with a similar(?) issue. But, it will play with ffplay as usual if you start from the beginning. But if you pass seek parameter, you will see ffplay will won't play properly & can see the similar errors.

Just encode as I have mentioned & try the following

ffplay -ss 5 out.ext

Edit:

Just use ffmpeg streamcopy with seek on previously encoded file with 8x8dct enabled to get a file with this issue. You will get similar error when you play the file with ffplay (without seek now)

ffmpeg -ss 10 -i out.ext -c copy out2.ext

Note: Older ffplay versions (at least 3.2.4) are working fine. But, all 3.3 & 3.4 versions will have the issues in playing the videos that was encoded with 8x8dct enabled. Videos encoded with ffmpeg wich has newer x264 encoder will not produce such files as they force disables 8x8dct when you encode to a video with 4:4:4 Chroma subsampling.

[Terran Vigil]

Replying to cehoyos:

Please explain how - exactly! - I can produce such a file.

See my comment above on how to reproduce as well as the commit that introduced the issue.

[Carl Eugen Hoyos]

Needs -x264_build 150