Avidemux Vs WMP Sync Issues

[Greyback23]

Salutations y’all it’s been quite a while.

I’ve been doing video editing a bit more frequently of late, using Avidemux
as honestly it’s the best option I’ve found so far that doesn’t
have usually a draw back save for the time it takes but that’s
every program so far and I have a lot of time to wait. And yet
I’ve come across something I cannot explain but I’ll try my best:

I started converting MKVs to MP4, managing to sync the audio of
a dual audio file that was running slightly ahead with the audio,
it works perfectly in avidemux and even VLC
player oddly enough. But here’s where it gets confusing. I started
having issues, the audio wouldn’t sync as it usually has every time
I use WMP (Windows Media Player).

Now when I cut a small few seconds or even a minute section from
the converted MP4s, run them through again and add say 300
milliseconds+ shift to it, the syncing is perfection. But the
moment I do the same with the entire MP4 video, the sync is out
by a few seconds again.

I can’t figure out what the issue is. It’s probably WMP but I’ve used
it for years and it still beats most others I’ve tried.

I don’t get why the sync works on a small cut portion even in WMP
but the complete file from start to finish goes those few seconds out
of sync. I’ve been trying to convert these episodes for almost 2 or 3
years+ and finally got around to it, but this is somewhat stopping
me after I have literally spent hours searching for the perfect copies.

Any ideas how to solve this? Or even how to fix WMP?

Funny fact: if I have Bluetooth headphones attached the audio sync
is almost if not dead on point even with WMP. But without them, it
fails once again.

I’ve tried updating codecs, restarting, re-converting, disabling and
re-enabling different audio drivers and everything I’ve come across
that was suggested. The shift refuses to work when I try to run it.
I even disabled the WMP option to drop frames to keep it all
in sync. It doesn’t do a thing to help

Any assistance or anything would be appreciated..

[hello_hello]

Can you upload a sample MKV and MP4? I assume it'd be better to upload samples without removing/cutting anything from the beginning, as that's a factor in the audio-sync problem, but just 10 or 20 seconds or something of each from there.

For the original MKVs, try opening some with gMKVExtractGUI to check for a delay. Both the video and audio stream can have a delay, and if a video delay isn't being applied when converting to MP4 that can mess with the sync. The streams should show 2 delay values. One is the actual delay, and for the video the other is the delay relative to any audio delay, and for the audio stream it's audio delay relative to the video, or something....

If you see zero ms twice for each stream, there's no delay.