Replace audio in mkv video

[tomkat2010]

I have a mkv video in 720p but with czech language and also a dvd version of the same movie in mp4 but in english. Im trying to dub the english over the high def version. Trouble is the dvd version (english) is shorted in length as the 720p version has about 1 min of filler at the start. Ive cut the audio from the 720 version and pasted it into the english version at the right time so should be in sync, but when exporting in Audacity to either mp3 or wav and then remuxing the audio is 1) out of sync and 2) very faded/washed out and sounds like its in the background. Can anyway recommend any other ways to do this bar an actual video editor timeline edit?

[aedipuss]

you could try mkvmerge gui. open the mkv, uncheck the audio, add the mp4, uncheck the video. click on the mp4 audio, go to the bottom panel and adjust the delay. you might need to do it a few times to get the correct delay by trial and error.

[redwudz]

What I have done is use tsMuxeR to demux the file, then add the new audio to Audacity, along with a silence padding (~1min in your case). You may need to adjust the audio level in audacity. You should be able to drop the other file into Audacity to see what levels it was at. I export in AC3 as I always had trouble with MP3, especially if it was encoded with variable rate audio. That can cause serious sync problems.

Then remux the new file back together with MKVtoolnix (MKVMerge) to output as MKV again.

I'm sure there are much better ways to do this, but it has worked for me.

[tomkat2010]

Thanks for the replies but no luck. I tried merging the clip and altering the delay so that its in sync, this works...but then the rest of the video is out of sync. I tried Cyberlinks Power Director and painstakingly reedited the soundtrack to it precisely, but again even though one part is in sync (say 5min in) later on is out of sync. I dont understand it!
The video is "Kooky" the animated feature if anyones familiar with it.

[Lowlander]

I did quite a few "add-audio-from-dvd-to-hd-video"-jobs myself and found that, if there is more than a constant delay to take care of, getting everything in sync can be _very_ tricky. Sources of trouble are different frame rates and different edits of the same video, e.g. one video being from HDTV with cut out commercial breaks, variable bitrate audio, variable framerate video etc.

The easiest way to judge is to demux the audio from both sources and adding both files to Audacity (or similar) as seperate tracks.

You can adjust for any initial delay very easily, just by looking at the waveforms and time shifting the dvd audio to match the start of the original audio. Take note of the actual amount of time you've just time shifted in millisecs, because that is the value to enter as your audio delay in MKVmerge GUI as described earlier in this thread. Then scroll the audio to the right and check/listen to various parts if the rest of the audio tracks are in sync. If they are, Bob's your uncle. Remux.

If they are not - and I think this is the case here - check if the delay between the tracks constantly grows towards the end. Then you can "measure" (= select) the exact (= zoom in!) time between one significant audio event at the very beginning and one at the very end of the original track, look for the same events in the out-of-sync track, measure the time between those and calculate from the two measurements the numeric factor to enter in MKVmerge's "Strech-by" field. Example: If the time between the first and the last spoken word in the original audio track is 5679.23 secs and the time between the same words in the out-of-sync track is 5683.64 secs, stretch by "567923/568364". If the numbers aren't too big, this can be entered exactly like this. Don't forget to enter any constant delay you found earlier, remux. Best part is: I've seen this actually work!

If the delay between the original and the out-of-sync audio floats back and forth, you may actually be screwed, go out and buy a BluRay of it. Or undergo the potentially frustrating task - still in Audacity - of editing the out-of-sync audio into pieces and matching those to the original track one by one. Good luck!

I personally prefer matching an audio track to another (known to be in sync) audio track over matching an audio track against the video itself. I think this is a matter of taste.

[tomkat2010]

Tried in vain, still out of sync and if I edit along the timeline Im left with gaps of silence. Id buy the bluray but its only available in a czech language, the dvd is in english (hence my re-edit). Anyone here up to the challenge?

[Lowlander]

You say you are left with gaps of silence which shows us that the dvd audio is too short. If the 720p video is from a Bluray and the DVD is PAL, the difference might be 24 versus 25 fps in frame rate, which puts off the audio by about 4 percent.

I'm not very much into patching video frame rates, but it may be worth a shot to patch the video (or even recode it for a test) to 25fps to see if it matches the DVD audio better. Let's still assume we are talking about the same cut of the movie in both videos.

Another approach might be to address the subject from the audio side, keep the 720p video untouched and stretch the dvd audio to match the 720p video's frame rate.

[tomkat2010]

I had a look at the frame rate and both sources are at 25fps. The gaps I referred to are when I edit one part of dialogue to a scene so its in sync, the rest is out so although I can edit it in sync there wouldnt be constant noise, just gaps until it reaches the synced audio. Its weird.

[tomkat2010]

It does appear the Czech version is longer maybe a cut english release. Thats probably why it isnt syncing.

[miolovers389]

Hey, Sorry if i'm late to answer. to Sync... audio and video. We must know what FPS in that video (Sorry again if bad english).

Open video (before mixed) with any media player, example media player classic. if done "Right Click" and choose Properties. After Windows Properties in opened click again tab "MediaInfo".

And then in MediaInfo, find the FPS number of video. it Must Same in MkvMerge, because if just little different can change the quality video.

Example: In MediaInfo, FPS video 23.967 and MkvMerge just 24Fps , and you choosing 24Fps in MkvMerge. The Video can affect. THE SOLUTION just type fps 23.967 in MkvMerge.

[tomkat2010]

Thanks for that, both videos (the bluray version and the english dvd version) are 25fps.
Ive tried editing in other timeline programs with just the audio but its the same.

I think you could have a point if the sync was around 2 seconds out, but its around 10 seconds out.

For example you can sync the audio perfectly one one scene and this (should) be correct for the rest of the movie, but skip ahead like 5 minutes and it out so you cant get it right.

[tomkat2010]

As a footnote I'd just like to say thank to the above poster as the advice on checking the fps worked. Within Windows both videos were 25fps but when in MKV merge the detail was that it was around 23.97fps, I altered this and it synced fine. So many thanks! I find it odd how it affected the timing so drastically though.