Closed Captions broken with h264_qsv encoder

[Sawgr]

Summary of the bug:

Ffmpeg 3.2 has -a53cc turned on by default. It works perfectly well when encoding with libx264. Closed Captions from mpeg files are inserted into the resulting mp4, and they can be turned on or off when playing the file in VLC, any other media player or even Apple TV.

3.2 is supposed to include the same functionality when encoding with h264_qsv (Intel QSV hardware acceleration), but it seems to be somehow broken. Captions are included but they are all messed up. Some words show up, some are just gibberish.

How to reproduce:

% ffmpeg.exe -i "Test.ts" -f mpegts -c:v h264_qsv -c:a:0 libmp3lame -b:a:0 128k Out2.mp4
ffmpeg version N-82579-g28d8789
built on 20161120

[Sawgr]

Log Report

[Sawgr]

Subtitles as extracted after h264_qsv encoding

[Sawgr]

Subtitles correctly extracted after libv264 encoding

[Sawgr]

Original MPEG TS: ​https://www.datafilehost.com/d/2023377c
libx264 encoded file (right Captions): ​https://www.datafilehost.com/d/afe2151a
h264_qsv encoded file (wrong Captions): ​https://www.datafilehost.com/d/12552886

[Carl Eugen Hoyos]

Is this issue also reproducible with 0eac93da?

[Sawgr]

I'm kind of new to this, so I don't really have an answer to that... Any way I can help?

[Carl Eugen Hoyos]

Checkout the relevant version, compile it and test with -a53cc 1

$ git clone https://git.ffmpeg.org/ffmpeg.git ffmpeg
$ cd ffmpeg
$ git checkout 0eac93da
$ ./configure --enable-libmxf
$ make ffmpeg

[Carl Eugen Hoyos]

Or please test this binary:
​https://ffmpeg.zeranoe.com/builds/win32/static/2015/ffmpeg-20151130-git-7b11eea-win32-static.7z

[Sawgr]

Replying to cehoyos:

Or please test this binary:
​https://ffmpeg.zeranoe.com/builds/win32/static/2015/ffmpeg-20151130-git-7b11eea-win32-static.7z

This binary gives me a "Unknown encoder 'h264_qsv' " error. I'm going to try and compile build 0eac93da

[Sawgr]

Trying to compile 0eac93da. I'm stuck at "./configure --enable-libmxf". I assume it's libmfx instead, but in any case I get "libmfx not found using pkg-config". Sorry. this is all new to me, help much appreciated...

[Sawgr]

Still stuck. Can anybody help me compile 0eac93da and I'll do the testing? Thanks

[Carl Eugen Hoyos]

Please test this binary:
​https://ffmpeg.zeranoe.com/builds/win32/static/ffmpeg-20160301-git-1c7e2cf-win32-static.7z

[Sawgr]

Thanks. Tested with different samples, -a53cc enabled. Captions still come up totally messed up. Timing is also incorrect. Here's a transcript of the first few seconds:

1
00:00:00,735 --> 00:00:03,102
m go m hogeme

oo smen Ian s can

2
00:00:04,905 --> 00:00:07,573
eal th teahi oka ty?kaWe
nyto afoonnynor llw, aht rll?h y

3
00:00:09,043 --> 00:00:10,576

Ok, yeahOk

loahI veoulo yo.ouoo

[Carl Eugen Hoyos]

Does the issue disappear if you disable B-frames?

[Sawgr]

I think you are in the right track. Disabling b-frames (-bf 0) gives a way better result. Not yet perfect, but almost readable. This is what I get (as opposed to the text on comment 11). Please let me know what to try next:

1
00:00:00,768 --> 00:00:02,001

I'm gonna get home

s s sas Ian

2
00:00:02,103 --> 00:00:03,235

toeaeaeawith this, okay?

3
00:00:03,337 --> 00:00:04,903

We can deal with thitogeer.

4
00:00:05,006 --> 00:00:07,706

Just don't say anything

to anyone r w, all right?

[Carl Eugen Hoyos]

No more suggestions from me, sorry.