How to extract audio from MKV file without delay?

This is probably the most newbie question of the century, but here goes.
I'm trying to extract files out of a MKV container and not having much luck. I have previously used gMKVExtractGUI with no issues, but now I've suddenly got two files it just won't work well with.

One MKV contains MPEG2 video and AC3 audio and the other one MPEG4 video and AAC audio. The videos seem to extract without issues, but the audio results in files which won't play in sync with the video. The extracted audio and video are not even of the same length and they contain the word DELAY in the extracted filenames.

So basically I would like to know how do I extract from a MKV container which result in files which play in sync and have the same length?? Preferrably with some type of software that is free and (if possible) does not re-encode or lower the quality of the extracted video / audio.

Try clever FFmpeg-GUI, then you will have more information about the individual stream durations and any delays.
You can also use it to extract, re-encode and mux all or individual streams.


[Attachment 77914 - Click to enlarge]

[Attachment 77915 - Click to enlarge]

What do you want to do with the extracted streams?
Do you want to replace the audio/video tracks?
If so, you also need to consider the frame rates of the videos.
Tell us exactly what you want to do.

Originally Posted by ProWo

Try clever FFmpeg-GUI, then you will have more information about the individual stream durations and any delays.
You can also use it to extract, re-encode and mux all or individual streams.


[Attachment 77914 - Click to enlarge]

[Attachment 77915 - Click to enlarge]

What do you want to do with the extracted streams?
Do you want to replace the audio/video tracks?
If so, you also need to consider the frame rates of the videos.
Tell us exactly what you want to do.

Thanks for replying. I tried it, but it ends up the same way in that software too.
For example this one file I have, it's 23 minutes and 12 seconds long. After I extract the streams in clever FFmpeg-GUI, I end up with an *.aac audio file that is only 23 minutes and 9 seconds long.
When I open the file in clever FFmpeg-GUI, it doesn't display any delays or as much information as the file in your example (see my attached image).


[Attachment 77927 - Click to enlarge]

What I'm trying to do is use the extracted audio when editing a different video in another video editing software, but the audio needs to be the exact same length as the original.

Originally Posted by ProWo

I think, the audio IS 23 min, 9 sec long.
In the start window from clever Ffmpeg-GUI, after loading this video, is there shown any audio delay?

Well, the video is 23 mins and 12 secs so the audio should be the same. Also, the extracted 23 mins and 9 secs file cuts off at the end before the song that is playing has a chance to stop so it's definitely not complete.
I can't see anything about an audio delay within FFmpeg. Is this the correct screen (the start windows)?

[Attachment 77931 - Click to enlarge]

Originally Posted by Ennio

What I'm missing in your initial post is what your target is. I have a hunch that you want to mux audio from file A with video from file B.

Hi! No that is not what I'm planning on doing. I need it for something I'm editing in a different software, I just want it to be the full version and not one that cuts off the ending by 3 seconds.

Originally Posted by guy24s

Well, the video is 23 mins and 12 secs so the audio should be the same. Also, the extracted 23 mins and 9 secs file cuts off at the end before the song that is playing has a chance to stop so it's definitely not complete.

Does the audio play to end in the Episod 1.mkv?

Originally Posted by guy24s

This is probably the most newbie question of the century, but here goes.
I'm trying to extract files out of a MKV container and not having much luck. I have previously used gMKVExtractGUI with no issues, but now I've suddenly got two files it just won't work well with.

One MKV contains MPEG2 video and AC3 audio and the other one MPEG4 video and AAC audio. The videos seem to extract without issues, but the audio results in files which won't play in sync with the video. The extracted audio and video are not even of the same length and they contain the word DELAY in the extracted filenames.

So basically I would like to know how do I extract from a MKV container which result in files which play in sync and have the same length?? Preferrably with some type of software that is free and (if possible) does not re-encode or lower the quality of the extracted video / audio.

I suspect each audio stream was muxed in original MKV with different parameters.

1. Extract audio streams with mkvcleaver
2. Mux them into one wile with mkvtoolnix adjusting attributes there for each stream like fps, delay etc
3. Play output file switching to different audio streams to see all is in sync. If not, go to point 2 again and repeat until everything is in sync

Originally Posted by ProWo

Originally Posted by guy24s

Well, the video is 23 mins and 12 secs so the audio should be the same. Also, the extracted 23 mins and 9 secs file cuts off at the end before the song that is playing has a chance to stop so it's definitely not complete.

Does the audio play to end in the Episod 1.mkv?

Yes it does.

Could you upload this video and post the link here?
I'ld investigate on this strange case.

Originally Posted by tuskacz

I suspect each audio stream was muxed in original MKV with different parameters.

1. Extract audio streams with mkvcleaver
2. Mux them into one wile with mkvtoolnix adjusting attributes there for each stream like fps, delay etc
3. Play output file switching to different audio streams to see all is in sync. If not, go to point 2 again and repeat until everything is in sync

I tried step 1 and ended up with the same as I did in FFmpeg, a file that is 23:09 in length. The funny thing is that when I play the file in for example Media Player Classic, it plays until 23:09 and stops, but the audio keeps on playing to the end. Basically the file reaches 23:09 and stops, but I do hear the last 3 seconds coming out of my speaker. But when I open the file in my editing program, it just cuts off at 23:09 and I don't hear the last 3 seconds of the middle of the song.
Unfortunately I couldn't do step 2 and 3, I am not that familiar with mkvtoolnix and how to adjust the streams. I probably will just end up converting the whole MKV file to MPG or something and extract the audio that way. I was hoping to get it without having to re-encode it, but this just seems like too much work.

After adding the video to your editor, add 3 seconds at the end. Then import the 3 second longer audio.

Another possible option would be to open the audio first, then import the video.

Originally Posted by jagabo

After adding the video to your editor, add 3 seconds at the end. Then import the 3 second longer audio.

Another possible option would be to open the audio first, then import the video.

I think I figured a solution that will work for me. Thanks everyone who has been helping me!
PS: jagabo, I sent you a private message a couple of weeks ago asking for help on an audio file, did you get my message? I decided to write directly to you because you helped me with a similar audio file problem in the past and the results were so good. Whenever you have some time, take a look in your inbox.

Originally Posted by guy24s

This is probably the most newbie question of the century, but here goes.
I'm trying to extract files out of a MKV container and not having much luck. I have previously used gMKVExtractGUI with no issues, but now I've suddenly got two files it just won't work well with.

One MKV contains MPEG2 video and AC3 audio and the other one MPEG4 video and AAC audio. The videos seem to extract without issues, but the audio results in files which won't play in sync with the video. The extracted audio and video are not even of the same length and they contain the word DELAY in the extracted filenames.

So basically I would like to know how do I extract from a MKV container which result in files which play in sync and have the same length?? Preferrably with some type of software that is free and (if possible) does not re-encode or lower the quality of the extracted video / audio.

Have you tried loading your video into mkvtoolnix, unchecking all entries except the audio you want, then saving it? It will give you an MKA file that you might be able to process elsewhere. Just a thought.

Originally Posted by Moralez

Have you tried loading your video into mkvtoolnix, unchecking all entries except the audio you want, then saving it? It will give you an MKA file that you might be able to process elsewhere. Just a thought.

Yes that was the first software I tried it with.

Originally Posted by guy24s

I think I figured a solution that will work for me.

I suggest you explain what you did for the benefit of someone who might have a similar problem in the future.

Originally Posted by guy24s

PS: jagabo, I sent you a private message a couple of weeks ago asking for help on an audio file, did you get my message? I decided to write directly to you because you helped me with a similar audio file problem in the past and the results were so good. Whenever you have some time, take a look in your inbox.

Sorry. I'm not around much these days so I forgot to address your PM. I suggest you post a sample in the forums here. I'm not real familiar with ffmpeg's aexciter filter so I can't answer off the top of my head. I seem to recall that I used a spectrum analyzer to see where frequencies were dropping, set aexciter to boost frequencies above that, and finally fine tuned all the settings until I got something that sounded good.

Originally Posted by jagabo

I suggest you explain what you did for the benefit of someone who might have a similar problem in the future.

Sure, but nobody will probably like to use my solution as I ended up going a lossy route; I just converted the whole file to MPEG2 and after that I could extract the audio. The destination project that the audio was going to be used with was an MPEG2 file anyway. I just had to get this done kinda quick and it seemed too complicated for me to get it working in ffmpeg.

Originally Posted by guy24s

I suggest you post a sample in the forums here. I'm not real familiar with ffmpeg's aexciter filter so I can't answer off the top of my head.

No worries, that is what I did and I did get some help.