Shifting audio for MP4 not working with avidemux

[markbc]

Hello,

I've searched and tinkered for hours but haven't got a resolution yet, so I'll post here.

I have a GoPro sports videocamera camera that makes MP4's. The audio is terrible so I record an MP3 file separately with my Edirol audio recorder. I have successfully brought these two files together in Yamb, deleting out the old audio file, to get a nice MP4 file as a result. Of course, the audio will need to be shifted. I open it up in Media Player Classic to determine that for example I need to shift the audio by +9000 ms.

Then I open up the MP4 in avidemux and I tick the shift audio box and enter 9000. But when I play the file it isn't shifted, and when I save it it isn't shifted. How do I actually get it to do this?

Thanks very much for any assistance.

[davexnet]

Perhaps a bug in Avidemux. If you shift the audio 9 seconds forward, in theory
there should be be 9 seconds of silence at the beginning of the video.
Try reporting the problem at their forum:
http://www.avidemux.org/smf/

[markbc]

Thanks. I get the following warning message when opening the file:

"H.264 detected

If the file is using B-frames as reference it can lead to a crash or stuttering. Avidemux can use another mode which is safe but YOU WILL LOSE FRAME ACCURACY.

Do you want to use that mode?"

I have the problem wither way. When I play the clip it is stuttery.

Are there any other programs that will do the audio shift?

Thanks

[davexnet]

If you don't mind switching to MKV, mkvmerge will work.

[markbc]

Yeah I tried that too but Wordpress doesn't support mkv. Maybe there's something I can do with avi.

http://en.support.wordpress.com/accepted-filetypes/

.mp4, .m4v (MPEG-4)
.mov (QuickTime)
.wmv (Windows Media Video)
.avi
.mpg
.ogv (Ogg)
.3gp (3GPP)
.3g2 (3GPP2)

[davexnet]

If you can get the timing right in the MKV, demux it using MKV extract GUI, then put it back into the
mp4 using YAMB.

Alternatively, use AVIdemux to get it back to an mp4.

It's a bit long winded, but I'm not aware of an other program that will work on the mp4/audio delay directly.

[poisondeathray]

yamb can shift the audio directly, select audio track , hit properties

in avidemux did you hit enter ? try a 2.6 beta build, it handles h264 better
http://avidemux.razorbyte.com.au/

9 seconds is a lot. It might be better to insert silence (if you're shifting that direction) and/or cut video or audio

[markbc]

Well nothing seems to be working.

I tried shifting it in Yamb by entering 9000 in the Media Shift space, which didn't work. I then tried entering 9 in case the units are seconds and that didn't do anything either.

I used mkvmerge to successfully delay the audio by 9 seconds, and create an mkv file. But then I could not get this to stick when I converted this back to mp4. The audio always resets to zero. I downloaded the 64 bit avidemux because I had the 32 bit version before but this made no difference.

Alternatively, since the audio always seems to want to set back to zero, can I just snip the video down by the same amount I want to shift the audio up? Then I can slice and dice the file as needed. How do I do that? Or, how do I insert 9000 ms of silence at the beginning?

[markbc]

Well I tried snipping the file in avidemux and was having a real frustrating time with the error message on saving that the start frame isn't an proper frame or something like that but I finally figured it out, I was able to snip a few seconds off the front of the file. So now I can bring that into Yamb and add the real audio. Finally! Thanks for the help, this is all very frustrating to learn but when you figure it out it's easy. There's my weekend gone ... but at least I figured out how to merge an MP3 with an MP4! I wonder what I'll learn next week.