MKVvextract stretches extracted audio/Audio not in sync with video

[cgo]

hey guys.

I'm having a weird problem with mkvextract. there is one specific .ac3 track in my .mkv which I can not extract properly. Let me show you first how the AC3-track looks INSIDE of the .mkv (Track ID 3):

Format                                   : Matroska
Format version                           : Version 1
File size                                : 748 MiB
Duration                                 : 20mn 39s
Overall bit rate                         : 5 065 Kbps
Encoded date                             : UTC 2012-01-15 12:39:53
Writing application                      : mkclean 0.8.6 ro from libebml v0.7.8 + libmatroska v0.8.1 + mkvmerge v2.3.0 ('Freak U') built on Sep  9 2008 17:43:22
Writing library                          : libebml2 v0.21.1 + libmatroska2 v0.22.1

Video
ID                                       : 1
Format                                   : AVC
Format/Info                              : Advanced Video Codec
Format profile                           : High@L3.1
Format settings, CABAC                   : No
Format settings, ReFrames                : 2 frames
Format settings, GOP                     : N=1
Muxing mode                              : Header stripping
Codec ID                                 : V_MPEG4/ISO/AVC
Duration                                 : 20mn 39s
Bit rate                                 : 4 132 Kbps
Width                                    : 1 280 pixels
Height                                   : 720 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 fps
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Bits/(Pixel*Frame)                       : 0.179
Stream size                              : 611 MiB (82%)
Language                                 : English
Color primaries                          : BT.709-5, BT.1361, IEC 61966-2-4, SMPTE RP177
Transfer characteristics                 : BT.709-5, BT.1361
Matrix coefficients                      : BT.709-5, BT.1361, IEC 61966-2-4 709, SMPTE RP177

Audio #1
ID                                       : 2
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Mode extension                           : CM (complete main)
Muxing mode                              : Header stripping
Codec ID                                 : A_AC3
Duration                                 : 20mn 39s
Bit rate mode                            : Constant
Bit rate                                 : 448 Kbps
Channel(s)                               : 6 channels
Channel positions                        : Front: L C R, Side: L R, LFE
Sampling rate                            : 48.0 KHz
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 66.2 MiB (9%)
Title                                    : GER 5.1 TVS
Language                                 : German

Audio #2
ID                                       : 3
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Mode extension                           : CM (complete main)
Muxing mode                              : Header stripping
Codec ID                                 : A_AC3
Duration                                 : 20mn 39s
Bit rate mode                            : Constant
Bit rate                                 : 384 Kbps
Channel(s)                               : 6 channels
Channel positions                        : Front: L C R, Side: L R, LFE
Sampling rate                            : 48.0 KHz
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 56.7 MiB (8%)
Title                                    : ENG
Language                                 : English

And here how that track looks after extraction with mkvextract:

Format                                   : AC-3
Format/Info                              : Audio Coding 3
File size                                : 59.1 MiB
Duration                                 : 21mn 31s
Overall bit rate mode                    : Constant
Overall bit rate                         : 384 Kbps

Audio
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Mode extension                           : CM (complete main)
Duration                                 : 21mn 31s
Bit rate mode                            : Constant
Bit rate                                 : 384 Kbps
Channel(s)                               : 6 channels
Channel positions                        : Front: L C R, Side: L R, LFE
Sampling rate                            : 48.0 KHz
Bit depth                                : 16 bits
Compression mode                         : Lossy
Stream size                              : 59.1 MiB (100%)

I noticed that inside of the mkv the duration of this track is 20mn 39s but the extracted one suddenly get's a duration of 21mn 31s. I tried a few options with mkvextract, --raw output or --fullraw output, nothing worked. I even tried it on different operation systems with different version of mkvextract but still no luck.

That's the reason I can't mux it up into a .mp4 container. Well I can but then the audio isn't in sync with th video anymore. And the problem is not smal delay it seems like mkvextrect "stretched" the audio, making it impossible for me to correct it with delaying back or forwards.

I hope some of you can help me out because I have lot's of files like this. I don't know what else to try. 1st I thought maybe the "header stripping" was the problem but it wasn't. I removed it with MKVtools and with MKVtoolnix. Tried even to "fix" the mkv with mkclean, nothing changed. I hope you can help me.

[aedipuss]

first i'd try to get the mkv to work without header stripping. get the latest mkvmergegui, uncheck header stripping. add the mkv, put checks in just the video, audio, etc. you want and have it re-mux just those parts. check to see if it's in sync. if so go ahead and try converting to mp4.

[poisondeathray]

Try muxing it directly e.g. mkvtomp4 or ffmpeg

[cgo]

first i'd try to get the mkv to work without header stripping. get the latest mkvmergegui, uncheck header stripping. add the mkv, put checks in just the video, audio, etc. you want and have it re-mux just those parts. check to see if it's in sync. if so go ahead and try converting to mp4.

thanks for the reply!

but I already tried that. I used 5.0.1 once and the latest one 5.2.* the remuxing progress went fine and everything was still in sync. But not after extracting/converting to mp4. Do you think the header stripping is the main problem?

[cgo]

Try muxing it directly e.g. mkvtomp4 or ffmpeg

thanks for the advice.

I tried mkvtomp4 but the audio is also not in sync with mkvtomp4. I think to problem with those muxers are that they all use mkvextract which causes the problem or changes the audio track.

I used ffmpeg with this command: "ffmpeg -i source.mkv -vcodec copy -acodec copy output.mp4"

but I got this error:

"[mp4 @ 0x7f9ccb011200] pts < dts in stream 0
av_interleaved_write_frame(): Operation not permitted"

What did I do wrong?

[poisondeathray]

you didn't necessarily do anything wrong with ffmpeg , might be some incompatibility in your file

you can try eac3to

eac3to input.mkv -demux

[poisondeathray]

Also what is the actual source? What was this mkv derived from ? Is it a "euro" source 25 fps ?

20min 39 vs. 21min 31 is almost the difference between 25fps and 23.976 fps .... might be some other funky business going on

It it a VFR mkv ? If so you will never get the MP4 in sync without making it VFR

Also note , mediainfo is not necessarily correct, all it does is read header information

[cgo]

thanks for your help!

seems like eac3to has extracted the ac3 file correctly, all I can tell right now is that the duration of the extracted ac3 file is correct. I'll try to put them into a mp4 container now as soon as possible but my external drive where all the files are just kind of died so I'm working an that now.

about the source I'm not quite sure. It's a little mixed up but the 1st audio track is german (I guess from europe) and the 2nd audio track (which makes problems) is definitly from US source.

video and 1st audio track are perfectly sync no matter what. Guess you're right about that 25 fps and 23,96 fps. Does that help us?

[poisondeathray]

Well try muxing it in as is first (from the eac3to demux) , if it's in sync, case solved


If not, and still there is a discrepancy in A/V length, you would have to convert either the video or audio to match (either fps of video, or stretch/shrink audio to match with an audio editor e.g. audacity, or eac3to can do it too)

(If it was "euro" source, the "english" audio might be already sped up)

Having more information about the source can often help. E.g. if this was Hollywood theatrical production, then the real original would be film rate, 23.976 (or 24000/1001 exactly) , but the mkv you have might have other processing done to it. But if it was BBC production, it might be 25fps

[cgo]

Well try muxing it in as is first (from the eac3to demux) , if it's in sync, case solved


If not, and still there is a discrepancy in A/V length, you would have to convert either the video or audio to match (either fps of video, or stretch/shrink audio to match with an audio editor e.g. audacity, or eac3to can do it too)

(If it was "euro" source, the "english" audio might be already sped up)

Having more information about the source can often help. E.g. if this was Hollywood theatrical production, then the real original would be film rate, 23.976 (or 24000/1001 exactly) , but the mkv you have might have other processing done to it. But if it was BBC production, it might be 25fps

eac3to did something with the ac3 file without reencode it, I don't know what exactly it did but it's far better as the extracted one with mkvextract. now it fits better with the video but it isn't 100% in sync. I'll try a few things with audacity now, thank you and please let me know something comes into your mind.

[poisondeathray]

can you post the eac3to log file ? it will say what has been done

is the desync constant (e.g. 1sec off the entire way) , or progressively worsening ? how much is it off by ?

was original mkv in sync (when you selected english audio track) ?

[cgo]

can you post the eac3to log file ? it will say what has been done

is the desync constant (e.g. 1sec off the entire way) , or progressively worsening ? how much is it off by ?

was original mkv in sync (when you selected english audio track) ?

yeah sure.
the original mkv was always in sync both of the audio tracks where in sync. maybe there's a funktion inside the mkv container which corrects the ac3 track somehow.

it's not constant delay and at the first few minutes I thought everything was in sync, but it get's worse. Maybe it get's up to 0,7sec-1,0sec I'm not sure Sound come earlier btw. Here's the eac3to log file:

eac3to v3.24
command line: C:\Users\****\Desktop\eac3to\eac3to.exe  D:\Downloads\source.mkv -demux
------------------------------------------------------------------------------
MKV, 1 video track, 2 audio tracks, 0:20:40, 25p
1: h264/AVC, 720p (16:9)
2: AC3, German, 5.1 channels, 448kbps, 48kHz
3: AC3, 5.1 channels, 384kbps, 48kHz, dialnorm: -27dB
[v01] The video track doesn't contain framerate information.  <WARNING>
[v01] Extracting video track number 1...
[a02] Extracting audio track number 2...
[a03] Extracting audio track number 3...
[v01] Writing new framerate "25fps" to bitstream.
[a03] Removing AC3 dialog normalization...
[v01] Creating file "source - 1 - h264, 720p.h264"...
[a02] Creating file "source - 2 - AC3, German, 5.1 channels, 448kbps, 48kHz.ac3"...
[a03] Creating file "source - 3 - AC3, 5.1 channels, 384kbps, 48kHz.ac3"...
[a03] Audio overlaps for 11ms at playtime 0:00:01.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:01.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:01.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:01.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:02.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:02.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:02.  <WARNING>
[a03] Audio overlaps for 13ms at playtime 0:00:03.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:03.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:03.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:03.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:03.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:04.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:04.  <WARNING>
[a03] Audio overlaps for 12ms at playtime 0:00:04.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:04.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:05.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:05.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:05.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:05.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:06.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:06.  <WARNING>
[a03] Audio overlaps for 13ms at playtime 0:00:06.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:06.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:00:07.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:00:07.  <WARNING>

[...]

[a03] Audio overlaps for 10ms at playtime 0:20:34.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:35.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:20:35.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:35.  <WARNING>
[a03] Audio overlaps for 12ms at playtime 0:20:35.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:36.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:36.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:20:36.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:36.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:20:36.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:37.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:20:37.  <WARNING>
[a03] Audio overlaps for 12ms at playtime 0:20:37.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:20:38.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:38.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:20:38.  <WARNING>
[a03] Audio overlaps for 11ms at playtime 0:20:38.  <WARNING>
[a03] Audio overlaps for 10ms at playtime 0:20:39.  <WARNING>
[a03] Starting 2nd pass...
[a03] Realizing (E-)AC3 gaps...
[a03] Creating file "source - 3 - AC3, 5.1 channels, 384kbps, 48kHz.ac3"...
Video track 1 contains 30970 frames.
eac3to processing took 5 minutes, 54 seconds.
Done.

does this say something to you?

[poisondeathray]

It means there were a bunch of audio gaps in track 3 (the english), that it tried to fix

Not sure what else to do, you'll have to play with ti

Or just leave it as is, is there any reason why you want to mux into mp4 ?

[cgo]

It means there were a bunch of audio gaps in track 3 (the english), that it tried to fix

Not sure what else to do, you'll have to play with ti

Or just leave it as is, is there any reason why you want to mux into mp4 ?

hmmm ok... what do you mean with ti?

mp4 just so I could watch it on apple tv. kind of important for me :/. I'll try the slowdown and speedup option with eac2to and see what happens.

[poisondeathray]

sorry, typo

"ti" = "it" ; play with it

[cgo]

sorry, typo

"ti" = "it" ; play with it

hey. I just tested the ac3 file with eac3to and the slowdown speedup options. turns out the speedup options is all i need to do and the audio is perfectly in sync with audio. you were right ac3 was in 23,76 fps and needed to be 25.00 fps.

thank you so much for your help. just one more question: do you know any other method to do this? I'm working on a mac and I couldn't get eac3to to work with wine. if not, thaks again and have good night!

[poisondeathray]

Well you can do it in any audio editor, it's just the ratio of 24000/1001 vs. 25.0

But I don't know if eac3to "fixed" something besides the slowdown (like gaps & errors)

or maybe avidemux ? there is a mac version

load the mkv, select the audio track, audio => set ac3 => then under audio filters set PAL to FILM => then audio=>save (enter name with extension )

EDIT: actually it's the other way around for you: FILM=>PAL

Alternatively, you can try muxing 24000/1001 FPS for the video, and keeping the audio as is