Converting MKV to MP4 Sync problem

[chang123]

Hi All,

I recently converted an 8GB MKV file to an MP4 file using VidCoder. I used the target size option to reduce the video to 1.8GB.
All went well and after 6 hours my new MP4 file was created. However, when I came to play it, I found that the sound was out of sync.

I am wondering whether I have all the setting correct. I converted to MP4 H264 with 30 FPS.The peak framerate box was checked with 2 pass encoding.


If that looks OK does anybody know why the sound would be out of sync?


Thanks.

[jagabo]

In what way is the audio out of sync? A constant error through the entire video? Does it start in sync then slowly get more and more out of sync?

[chang123]

No, It seems to be a constant error throughout the entire video.

[sekininsha]

I converted to MP4 H264 with 30 FPS...

and tell me ... the mkv is also is a 30 fps ?

[jagabo]

No, It seems to be a constant error throughout the entire video.

Then just change the audio delay/advance. If the program doesn't let you do that then remux with a tool that does.

I would also recommend using constant frame rate, same as source.

[chang123]

Hi,

Not sure whether the original MKV is 30fps, I'll have to check. If it isn't then might that be the problem?

Thanks jagabo for your recommendation to change the frame rate to constant as apposed to peak. I'll have to give it a go and see what result I get.

[jagabo]

Not sure whether the original MKV is 30fps, I'll have to check. If it isn't then might that be the problem?

That's probably not the source of the A/V sync problem. If you specify a higher frame rate than the source the program will duplicate frames to keep the same running time. If you specify a lower frame rate than the source the program will discard frames to keep the same running time. Either way, you will get jerky video. So you want to keep the same frame rate as the source.

[chang123]

Ok thanks. I need to change the fps to the same frame rate as the source. BTW the video wasn't jerky, it was just a little out of sync on the audio.