An app to visually sync audio to video similar to Subtitle Edit visual sync

[cinesimon]

Hi all,
Recently I muxed an 23.976fps video to audio that came from a 25fps video - to get the best quality.
Problem is, after converting the video to 25fps(with mkvmerge) to match the audio, and matching up a time difference, they're still out of sync - I can match them at the start, but the audio gets more and more out of sync.
I have no way to quantify this, so can't see how I can stretch it via mkvmerge as it requires numerical values of course.

Does anyone know of an simple and easy to use application that uses a visual sync system such as the dual-screen visual sync system that Subtitle Edit uses?
The audio is ac3 5.1, if that matters.

Thanks in advance for any help,
Simon

[Bjs]

More out of sync is correct ... then don't change the video's fps.

Use audacity > effect > change speed ... - values stretches ... you only need to calculate the % difference between video and audio.

[AlanHK]

I'd use Audacity:
Load both audio tracks.
Use the "change tempo" effect to stretch/compress the new audio so it matches the original.

Delete the original track, save the new one as AC3, MP3 or whatever and mux it in.

[jagabo]

I can match them at the start, but the audio gets more and more out of sync.
I have no way to quantify this

Sure you do. Determine how far out of sync the two are near the end of the video and calculate a ratio. For example, if the video is 3600 seconds long and the audio is 15 seconds ahead of the video near the end, then you have make the audio 3600 / (3600-15) longer -- 1.004184.