Hello there & this is my first post here:
Thx for allowing me to join & I don't usually have problems with software and how they function but when I am stumped I do ask for assistance.
My situation is this......I do dl various mkv files and most of them are compressed Blu ray movies. These mkv files can be from anywhere on the planet and most are created where the default language (audio) is not English. My media player of choice is WMP classic Cinema Series as it seems to be capable of playing just about anything troublefree whereas VLC or GOM or MPlayer have troubles with 1080p/720p files.
I am using the MKVToolnix program which contains all of the MKVmerge essentials to edit the contents of the mkv files. What I do in all cases is to remove the foreign languages and then make English the default audio for my purposes.
Now these files play without issue (in most cases) as they are received. A few have had some playback issues with repeating video glitches (incorrect reframes settings?) or audio out of sync problems (the audio problems I have been able to correct).
What I am coming across is a syn problem? when I extract all of the files I want to keep (h264 video & either the DTS or AC3 audio) and then let mmg remux these back together to create a new mkv file.
What I get will be a new mkv file that now has a video problem where glitches are present and is unwatchable.
I've tried repeated attempts slightly altering the video sync by introducing a small delay or doing a small stretch to see if this resolves the problem.
When the vid & audio are extracted the DTS or AC3 audio file will play as it should do through WMP classic, but the h264 video file fails miserably.
What I want to know is...should MKVMerge upset the sync of both video & audio files so that when you mux everything back together again you end up with a file that is now basically corrupt?
I'm using MKVToolnix 4.5 (lightspeed)... no errors are displayed at any time the programs run thru their various duties.
Any suggestions would be appreciated as I'm baffled as to whether it's something I am doing or there is a problem with the original mkv file as it was created.

Thx very much, Steve