Can you change Aspect Ratio in Avidemux without reencoding?

[tokintmash]

These are interlaced H.264 streams which I have copied into MKV container (from MPG) using Avanti. Although I did choose 4:3 as the aspect ratio in Avanti, they appear to be something else (maybe square - narrower) in Avidemux and in VLC too. Can I do something about it without reencoding?

[poisondeathray]

Not in avidemux without re-encoding

Try mkvtoolnix

[tokintmash]

Yes, well I used to do this with mkvtoolnix but I am desperately looking for and alternative because mkvmerge has no preview window, plus audio and video are progressively going out of sync.

Until now I have:

1. demuxed audio/video
2. muxed them again in mkvmerge
3. then streched the audio to sync
4. then played the clip in a player and marked the timecodes to split at
5. then split
6. then merge the ones I want again

It is all a lot of work. Plus streching to sync is not perfect and results in clicks between clips. This is footage from my helmet camera, so I cut a lot and it is driving me nuts

I managed to directly copy audio and video into MKV container in Avanti. In this case audio and video stay synced but for some reason MKVmerge is not able to work with these files anymore. The problem seams to be with audio codec. This is the error I get if I try to merge two of these MKV files - "Error: track 2: Malformed codec id 'A_AAC'".

How is it different if I demux and mux or just copy streams?

[poisondeathray]

Yes I remember your original topic
https://forum.videohelp.com/topic364743.html

You can try h264info on the raw avc stream to set DAR flags

Also you might try different ffmpeg versions, some may work better; or even compile a specific version yourself. Maybe they fixed something by now...
http://ffmpeg.arrozcru.org/autobuilds/

If there are timecodes, demuxing into raw avc stream will sometimes cause sync errors. But if the "copy stream" doesn't work properly, then you might still get errors

Your files are non standard, that seems to give all the usual software problems.