Avidemux driving me crazy!

[JimJay]

I have an mp4 to shorten and I need it to trim the first 1:08 minutes. I've set the Start point at 1:08, both by dragging and by listening just to sure. However, when I hit Copy it keeps ignoring my designated start point and insisting on starting only 36 seconds in - I've rerun it 20+ times and tried it on a fresh copy of the original mp4 but it still won't do it. I've also tried truncated the file it produces but although it again shows that I'm about to truncate another 32 seconds it starts at at the beginning of the previously-truncated clip, ie at 0 seconds (the old 36 second point in the original). I'm using 2.7.5.

Can anyone shed any light on where the program's - or my - screw up is, please?

And if anyone can help with an associated problem: the Avidemux Forum tells me that I'm "not allowed to register" - any idea why not? I'm in the EU, which might have something to do with it...

[DB83]

Well I just tested the process (same version) and all works fine.


Now it may well be that you are trying to shorten on a frame that is not an I-frame and the program is adjusting to ensure that the trim is starting on an I-frame.


All I can suggest is that you upload a trimmed sample long enough to assert if that is the issue or the file is corrupt in some way.

[DB83]

Another suggestion first.


Try remuxing the original both in avidemux (copy video audio mp4 muxer) and mp4boxgui to see if that fixes the clip.

[JimJay]

Thanks. I've just tried remuxing as you suggest but it hasn't made a difference. Just to be clear, are you suggesting producing two remuxed files, one via each program, or remuxing with avidemux and then remuxing that remuxed file itself with mp4boxgui?

[DB83]

Two independent muxed files - not one remuxed from another program.


But if that fails I still suggest you upload - as an attachment here - a two or so minute sample from the original. If the whole file is not too large (< 500 mb) you could even upload the whole thing.

[JimJay]

This is the beginning of the file - I'm trying to trim the first 1:08 off from the start but no joy. And to answer the question before it's even asked - it's in Bulgarian...

[jagabo]

The issue is that which DB83 mentioned in his first replay. In copy mode you can only cut on keyframes. In your video keyframes appear at frames number 0, 900, 1800, 2700... Those correspond to 0 seconds, 36 seconds, 72 seconds, 108 seconds... AviDemux simply picked the nearest keyframe before your selected cut point.

[DB83]

There is a solution if you must trim at that exact place.


The video has a high number of ref frames >> 11 rather than a more typical 4. You would have to re-encode the whole file - you can select AVC and then the resultant file has only 4 ref frames.


Here are two examples. The first has is a re-encode at 4 ref frames. The second is the original 11 ref frames but at the next I-frame (and, yes, the previous was several seconds earlier)

[JimJay]

Guys, many thanks for taking the time to look at this and reply! Hopefully I'll now be able to do what "the client" (okay, my Bulgarian wife ) needs...

[DB83]

Tell the 'client' make mine a large, no very large, Rakia


BTW Bulgaria one of my fav. destinations. Have several friends there.


As to your latter Q. which I have only just noticed, it may assist if you stated the exact issue with registering there - even tho it looks like a quiet place and you will typically get more help, and quicker, here. I have not tried to register there but like many places you have to give a valid email addr. because a validation email will be sent. And that may also be done manually by the admins rather than an automatic process - that happened for me with one forum and I waited almost 7 days for the mail