MKV mystery

[Zeroknight]

I have been attempting to convert a set of MKV files into AVIs. So far I have had very few problems.

Recently I have been working with a set that seems to have a problem.

The first four MKV files work correctly, and I had no problems converting them. However, the fifth file is a major pain.

When I play the MKV with Media Player Classic, it plays correctly. The audio and video synch as it should, and there appear to be no problems.

However, when I extract the audio and video from the MKV, that's when the problem starts.

No matter what I try, the audio doesn't synch with the video when I recombine the files into an AVI. I use VirtualDubMod and VirtualDub to recombine.

I've tried Time Stretch, ReSampling, complete reencoding... nothing seems to make the files match up. Yet, when I play the original file in the MKV container, they do match up.

Does anyone have any ideas? Is there perhaps a way to "capture" the video/audio as it is played? If there were it would fix my problem.

Any thoughts would be greatly appreciated.

[junkmalle]

Is the extracted audio VBR MP3? If so, put VirtualDub in Audio Full Processing mode and reencode it to CBR.

If the extracted audio is uncompressed PCM? If so, and it is off by a fixed amount throughout the video you can simply use VirtualDub's Audio Interleaving to skew it.

[Zeroknight]

Here's the thing; I tried reencoding the audio to CBR (I belive it is very VRB)... that did not work.

Here's another thing; VirtualDubMod warns me at the beginning that the VIDEO is VBR.. and that I should use a different program to deal with the video...

The audio is not off by a set amount. I already tried skewing the audio. The audio gets more out of synch the further into the video it gets (after remuxing).

[Dragonsf]

Have you loaded the Audio into a wave-editor and compared the run-length?
If the audio is not the same lenghth, the time lag will be increased progressily with each frame.

[laspis59]

Is there perhaps a way to "capture" the video/audio as it is played? If there were it would fix my problem.Any thoughts would be greatly appreciated.

Capture Pad.Turn off Hardware Acceleration in Options>Advanced
I'd use huffyuv for capture.

[Zeroknight]

Whulp.. I tried CapturePad... apparently my system is not powerful enough to actually use it with any degree of success

The duration of the audio file is different from the video file, so I understand about it becoming more out of synch the further into the video it gets. What I don't understand is how Media Player Classic can play it from the MKV file with zero synch problems, yet when I try to work with the seperate files I cannot get them to synch.

Sigh... I've started editing the audio file by adding creative silences to increase the time and manually synch the file. I know there must be a better way of doing it, but I can't for the life of me find one that actually works.

[Zeroknight]

Is there such a thing as an MKV converter that has the same reliability as Media Player Classic? Perhaps one that uses the same decoder so that it can reliably redo the contents without error?

[junkmalle]

The duration of the audio file is different from the video file, so I understand about it becoming more out of synch the further into the video it gets.

One place I've seen this happen is when converting variable video frame rate RMVB (Real Video) files. RMVB has a "repeat" frame type. When successive frames are identical it simply tells the decoder to repeat the last frame. VirtualDubMod doesn't seem to understand this and skips the frame. So at every repeat frame the video and audio get more out of sync.

The solution for RMVB files was to use AVISynth with its "convertfps" option. The script looks something like:

#ASYNTHER RMVB 23.976fps
DirectShowSource("filename.rmvb", fps=23.976, convertfps=true)

Change the filename and fps arguments to the proper name and value. Then open that script with VirtualDubMod.

You have to have a very recent version of AVISynth for this to work. And of course, you'll be reencoding the video.

[Zeroknight]

Well.. I tried reencoding the video.. no dice.

It's funny... I've tried at least twenty different encoders, I've redone the audio at least a hundred times, including "stretching" the duration... still no luck

Oh! I did find a way to encode the video and audio so that they match up... only one problem tho.. when I do that the video "gains" corrupted frames

Sigh.. it simply boggles my mind that the player has no problem with the entire video/audio thing, but the moment I try to change it, it all goes to that warm place down under...

[Zeroknight]

OMG! I found it!!!

Assuming you want to remake an MKV file into a DvD ready VOB set, here's what I did and it worked perfectly:

The first things you need to do are make sure you have the matroska codecs installed.

Next thing you need is mkvmerge GUI. Using this you change the MKV so it has only ONE video and ONE audio (assuming the file has multiple audio tracks). Unfortunately I do not know if this process will work if you leave subtitles in, as I despise subtitles and so haven't tested it (and prolly never will... ).

Ok.. once you have a new MKV file with single audio/video, you now load that file up in WinAVI! This marvellous program was able to convert my problem file when VirtualDubMod was unable to touch it (at least not correctly)!

I haven't tried making the problem file into an actual AVI, as my final goal was for DvD VOBs, but I imagine since the DvD aspect functioned like a charm, the AVI aspect would be the same.

So.. WinAVI was able to synch the audio and video in SPITE of the VBR video and audio AND in spite of the difference in length between the two.

Thank you everyone for trying to help me with this. I wanted to reply with my sucsess just in case someone else is having this problem. I like to give back when I can

[ChristianHJW]

Converting MKV files into old, outdated AVI files ? BS ....

If you want to make a DVD from your MKV, follow this guide http://www.matroska.org/technical/guides/dvd/index.html and report back to matroska-users AT lists DO matroska DOT org if it worked for you

Christian
matroska project admin
http://www.matroska.org