Sync problems when adding a new language to mkv movie

[gideva]

Hi there,

hope you can help me with this issue... I am trying to add spanish language to some movies (mkv files). I followed some guides but in the majority of the cases I cannot reach a decent result because the audio/video are completely out of sync.
Most of the times I have a mkv file (the good quality one) and an avi file (spanish soundtrack).

What I do is:

1) If the videos do not have the same frame rate I convert one of them with Handbrake so they can match
2) I extract the audio from the avi with MKVtools
3) I check the sync between the two videos with Avidemux (checking the frame/audio difference)
4) Resync the mkv and the audio track (using the correction obtained with Avidemux) with MKVToolNIX.

What am I missing?

Hope you can help me out

Thanks

[smrpix]

Step 1 is generally unnecessary as audio is based on time - seconds, milliseconds, not framerate.

You need to do a more detailed analysis of where your sync is failing. Put both tracks into an audio editor like Audacity and compare waveforms, particularly on sound effects and music that would be common to both language versions.

See if your sync is drifting over time or if the language versions of the film actually represent different cuts with different scenes.

Sync drift can be corrected in audacity by stretching the track, different cuts can be adjusted for by splitting, and slipping and sliding the tracks to their appropriate locations.

You can then output your modified Spanish language track and mux into the mkv as usual.

[gideva]

Thanks. I will try as you suggest