Syncing an audio track

[carlmart]

I am facing a problem that theoretically should be easy to solve... with the right tools.

There's a French film by Trauffat which has not yet been released in BD: La nuit americaine. "Day by night" in the USA.

I already have the original DVD, in French, and the most I could get in HD is an NTSC TV rip, which unfortunately is dubbed in English.

As the version I have is also NTSC, and the audio track times are just a few seconds apart, I thought I could be lucky and sync the HD video to the French audio track.

Found a clapper point at the beginning (it's a film about filmmaking, so it has lots of clapper points), and it goes fine for a long time but then slowly goes out of sync.

So I thought there might be way to shrink the audio track finding two points at each end.

What programs, besides professional ones, can do that?

I am familiar and used SoundForge and Audacity, but I'm not sure they can do that.

What options would you suggest?

Thanks!

[jagabo]

Audacity definitely has time stretch/shrink filters (with or without pitch change) Effects -> Change Temp or Change Speed. But this type of adjustment will only work if your audio tracks have a simple linear length change. Your description "goes fine for a long time but then slowly goes out of sync" implies this is not the case. You would want to keep the first part as-is, then stretch the second part. Of course, that's easily done by marking only the part you want to change. Releases in different countries often have different cuts of the movie, and different studio and distributor logos at the start. So you have to account for that too.

[carlmart]

I'm pretty sure this release, video wise, is exactly the same on both versions. Of course the logos are different, and one of them has the MGM lion on beginning and end.

But I synced the clapper 5 minutes from the beginning, and by the end is not that far in sync. What I don't know is if Audacity would allow me a shrink by adjusting the beginning and end points, in the video or audio tracks.

I was reading another Videohelp thread over this syncing matter, where I think you, Jagabo, advised adjusting the video track instead of the audio track. I should try both ways and see which one turns out better.

It worries me that adjusting the video track would involve adding or deleting frames, which might affect the video quality. Stretching or shrinking audio seems more "infinite" to me, no whole frames involved.

[jagabo]

In audacity you adjust the length of the video by a percentage, or total length (of the marked section). Either of which is easily calculated by knowning where the start and end are and where they need to be.

[carlmart]

In audacity you adjust the length of the video by a percentage, or total length (of the marked section). Either of which is easily calculated by knowning where the start and end are and where they need to be.

Can I do that in SoundForge? I think that on SF 11 you can load video too, it would be a much more accurate and faster way to sync all the audio.

[turk690]

This is how I would do it: after demuxing/obtaining the requisite audio and video, I lie them down on appropriate tracks in Adobe Premiere. I inspect the sync at various points throughout, paying close attention to dialogue and folley (because that's where loss of sync between audio and video is immediately obvious). Then I cut the audio into several segments (after I end up cutting I can have 10 to 100 segments for a 90min film). The points at which I cut are in parts of the film that are silent or where music and effects do not have to be in complete sync. Then these audio segments are finely moved about until they match the corresponding video. The end of each segments can be dragged and/or faded onto the next. One basis for this method is loss of sync can be tolerated if it's less than 5 frames difference. In many cases, a cut audio segment is perfectly sync'd in the middle and 2 or 3 frames out at beginning and end; still acceptable. Another reason is that temporally stretching/squeezing the audio is good if the sync drift is constant, the total number of frames known (total playing time difference between audio and video), and the audio editing program does not add artifacts of its own in its method of stretching/squeezing the audio. Failing all that, I just cut and reposition away.

[carlmart]

That's a path I wouldn't like to go by. I am a filmmaker, experienced sound recordist and sound editor, and I use Avid MC instead of Premiere.

But as I said I'm not sure if such a hassle would be justified. My query was for simpler tools that I might not know about.

[jagabo]

I think you, Jagabo, advised adjusting the video track instead of the audio track. I should try both ways and see which one turns out better.

It worries me that adjusting the video track would involve adding or deleting frames, which might affect the video quality. Stretching or shrinking audio seems more "infinite" to me, no whole frames involved.

I was suggesting he change the frame rate without duplicating or decimating frames. You can't do that if you need standard frame rates for DVD or Blu-ray, or whatever. But if you're just making a video for playback on a computer it's ok.

[netmask56]

Could it be a small frame rate difference ie DVD 23.976 and HD TV transmission say 24 fps?

BTW it appears to be released on Blu-Ray http://www.dvdbeaver.com/film5/blu-ray_reviews_68/day_for_night_blu-ray.htm

[carlmart]

That's very good news this Criterion release. Didn't know about it.

It might not be easy to get over here.

Jagabo, what I always author is an mkv file that I burn on a DVD. I play it through a media center or my BD player, so in a way it's like using a computer.

[bFooz]

Reaper has also time stretching functionality. Although it is an audio editing software, you can also load a video into it and it displays a waveform for audio from video too. You can timestretch the audio by dragging the edge and holding the ALT key.