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  #1  
Old 2007-12-25, 08:49 PM
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Stretching audio to sync with video

I got a DVD (in a trade) with camera audio and now I want want to sync it with soundboard audio. I have Vegas 7 and a fully functional 30-day trial of Soundforge, but I'm not sure what to do now. I figured out how to use Time Stretch in Vegas and I can come close with that, but it's still a little off. I could swear I saw a thread about this here not too long ago but now I can't find it. If somebody could point me in the right direction I would appreciate it.
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  #2  
Old 2007-12-26, 05:33 AM
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AAR.oner AAR.oner is offline
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Re: Stretching audio to sync with video

its better to stretch the video, as opposed to stretching the audio [which causes a noticeable difference in pitch]

you will probably have to make cuts in the video track and adjust it at numerous points to get everything to sync up proper
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  #3  
Old 2007-12-26, 07:31 PM
stantheman1976 stantheman1976 is offline
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Re: Stretching audio to sync with video

Quote:
Originally Posted by AAR.oner View Post
its better to stretch the video, as opposed to stretching the audio [which causes a noticeable difference in pitch]

you will probably have to make cuts in the video track and adjust it at numerous points to get everything to sync up proper
Not true. I've stretched audio a decent bit with Vegas and never had problems. It's better do stretch the audio.

Here are a couple options to check in Vegas. Go to Options > "Quantize To Frames". Make sure that is unchecked. If it is checked then when you stretch it has to be one full frame at a time. With it unchecked you can stretch in the smallest increment you want.

When you start your project go to File > Properties and under the Audio tab there is "Resample and stretch quality". Choose Best for that.

With these settings I have never had any problems syncing separate audio sources and stretching them as much as needed. Usually the drift between devices is not more than a few seconds so it's not a huge issue.
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  #4  
Old 2007-12-27, 05:17 AM
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AAR.oner AAR.oner is offline
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Re: Stretching audio to sync with video

i can typically hear pitch changes &/or warbles when done this way, even if using time stretch w/ pitch lock...the rule of thumb as an editor is to always speed adjust yer video tracks before making any adjustments to audio [only if absolutely necessary]

but if thats how you want to do it when authoring your own recordings, by all means
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  #5  
Old 2007-12-27, 07:01 AM
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Re: Stretching audio to sync with video

AAR.oner, you must have better ears than a bat I believe nobody writes here about difference in minutes but seconds or rather milliseconds with regards to particular song.

I believe that the cut the video option is no option at all. It's more annoying to have jumps and skips on video that a little problem with syncing, imo. Maybe not a big problem when the camera shows crowd but how do you want to cut on the band scenes?

Redpill didn't write what are his sources but even if both come from analogue tapes (VHS / cassette = possibly no constant speed) my advise is:

1. Don't import to Vegas and your audio editor SBD as one big file including all songs but each song separately.

2. Use Vegas to check where are the synching problems, and make a preliminary match but don't make any cut or use time stretch function. Vegas is good but not to make a perfect match, imo.

3. Export preliminary synced SBD to wav (one file, 16/48).

4. I use Adobe Audition for the final syncing but Soundforge perhaps has the same tools: import to Soundforge original audio, preliminary synced, and SBD with each song separately - they have to be converted from 44.1 to 48 kHz. Insert all three in the multitrack window. Preliminary synced audio serves for the SBD as a visual reference.

5. Position SBD tracks to match preliminary synced audio.

6. Before you start final syncing you may need to amplify video audio as usually - i.e. AC3 - is lower than SBD and may have no well visible picks.

7. Now start syncing SBD tracks with the video audio using first of all your eyes, finding identical picks and beats - see attached screenshot. (Some people use function for auto finding and marking beats to get matching points, however, I didn't find it useful in most projects I did.)

For each track/song find a matching pick at the beginning and at the end, and then use time stretch function to SBD to make them identical. Don't worry about crowd noise in between songs, it can be patched, mixed, cut or whatever to keep it with the overall time line.

Hope it helps,
Pawel
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  #6  
Old 2007-12-28, 05:28 AM
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Re: Stretching audio to sync with video

i never said "cut the video" pawel, i said time stretch the video before time stretching the audio...you can use keyframing to fine tune and smooth, no cuts are necessary

i'll re-iterate, I can usually hear speed changes to an audio track, even when we're talking frames...now whether or not the majority of folks who are watching can is of no concern to me, i can hear it and i'm not the only one -- this site has numerous other professional editors and audio engineers who i guaruntee could hear it as well -- thats what training is for...truth is, 99.9% of the time, its better to manipulate speed of a vid track and leave the audio track alone

but as i said, when yer authoring yer own ish, you can do with it what ya want
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  #7  
Old 2007-12-28, 07:22 AM
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Re: Stretching audio to sync with video

Quote:
Originally Posted by AAR.oner View Post
i never said "cut the video"
maybe I got you wrong (your 1st reply): you will probably have to make cuts in the video track and adjust it at numerous points to get everything to sync up proper

Redpill asked how to add SBD track to a DVD. If you propose to adjust video it means that it has to be re-encoded ...and then you may ban it as the site mod

Also, if audio stretching causes noticeable and incorrect pitch change it's damn obvious that there is something wrong with one of the sources, and that it's not worth to process.
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  #8  
Old 2007-12-29, 02:25 PM
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Re: Stretching audio to sync with video

i was thinking he was working with the raw footage...guess it was a bit too early for me to post that morning

so let me modify my answer, yes given the situation, and as long as the audio isn't off by much [preferably just a handful of frames], adjusting the audio is the way to go

however, given raw footage and not an authored dvd as the source, i still prefer to adjust the video speed as opposed to audio
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  #9  
Old 2007-12-29, 05:15 PM
Drummer247 Drummer247 is offline
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Re: Stretching audio to sync with video

I agree that you shouldn't 'stretch' the audio if you can help it. I'm only cheap and use 'Ulead Video Studio' heh, but when I sync and try to stretch the audio I hear little 'pops/clicks/warbles', etc and its rather annoying.

A good solution is to open the audio in Audacity and use the adjust tempo feature. There is a way to adjust the tempo of the track but without changing the pitch.

I'm no professional by any means but when I do this I can't hear any artifacts in the sound and it gets the job done (still hard work though). The tricky part is knowing by how much to change the tempo by and it takes some time guessing and trying different settings to get the perfect sync.
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  #10  
Old 2007-12-30, 08:30 AM
stantheman1976 stantheman1976 is offline
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Re: Stretching audio to sync with video

Vegas or any quality audio program can stretch audio while preserving pitch and tempo. Ulead is a decent beginner's tool but nowhere near as powerful as Vegas.
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  #11  
Old 2007-12-30, 08:39 AM
stantheman1976 stantheman1976 is offline
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Re: Stretching audio to sync with video

Quote:
Originally Posted by pawel View Post
maybe I got you wrong (your 1st reply): you will probably have to make cuts in the video track and adjust it at numerous points to get everything to sync up proper

Redpill asked how to add SBD track to a DVD. If you propose to adjust video it means that it has to be re-encoded ...and then you may ban it as the site mod

Also, if audio stretching causes noticeable and incorrect pitch change it's damn obvious that there is something wrong with one of the sources, and that it's not worth to process.
You do not need to re-encode to make it work. All you need to do is get the audio track synced with the video on the NLE timeline and make your adjustments. Then render only the audio track as 16 bit/48kHz PCM WAV. Import your original VOB or MPEG-2 file into your authoring program and choose your new audio stream to replace the existing audio. You've already made sure it's synced to the original video so you're good to go.
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  #12  
Old 2007-12-30, 08:43 AM
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Question Re: Stretching audio to sync with video

I'm of the thinking that if something doesn't synch correctly that both pitch and tempo (time) should both be stretched or compressed, like old school analog tape. Changing pitch without changing tempo or changing tempo without bending pitch would both cause artifacts, wouldn't they? Doing both is not nearly as harmful - it's just like playing a tape or a vinyl record a bit faster or slower.
Or am I way wrong?
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  #13  
Old 2007-12-30, 09:44 AM
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Re: Stretching audio to sync with video

Quote:
Originally Posted by stantheman1976 View Post
You do not need to re-encode to make it work.
You didn't understand: it was about stretching video, not audio.
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  #14  
Old 2007-12-30, 09:58 AM
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Re: Stretching audio to sync with video

Quote:
Originally Posted by Audioarchivist View Post
Changing pitch without changing tempo or changing tempo without bending pitch would both cause artifacts, wouldn't they? Doing both is not nearly as harmful - it's just like playing a tape or a vinyl record a bit faster or slower.
Of course but I have in mind only such A/V sources for which the process doesn't cause noticeable problems. As I wrote above, if difference between audio (track) can be measured in seconds, it's worth a waste bin only. You know that you won't hear milliseconds if correction is done well.

In my experience, the most frequent problem is caused by cuts on clapping, warm up between songs etc. So, it's not big, and can be corrected by patching from one of the source.
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