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[Help] Audio Syncing
#1
Dear Audio experts,

As some of you know, I have a 16mm Retroscan film scanner. I swapped out the 720p camera that came with it and replaced it with a 2K camera, so it captures some pretty good images. However, I'm not happy with the quality of the audio I am getting from AEO Light. So I recently tried capturing the audio using my film projector. That audio does sound much better but needs syncing to the video. Like all film projectors, this one is no longer brand new and judging by the issues I'm experiencing when trying to sync it, I'm guessing that it no longer runs at a constant 24 fps.

Normally, I would sync Audio from a laserdisc or DVD version of the film (that I do know how to do), but this is a TV Print of Airplane! so there are some alternate and extended scenes not in the home video version. Somebody did kindly share a TV Capture of Airplane which I may be able to use as an audio source, but I'm pretty sure this 16mm version is slightly different in at least one or two scenes so I'd really like to be able to use the print audio...

I'm pretty sure After Effects is not the best software for this, but I'll use it to demonstrate the problem:

[Image: ne9mN0f.png]

The top waveform is the AEO Light version, which syncs nicely, but doesn't sound very good at all. The bottom is from the projector. If I match the peaks and valleys at the start of the reel, it drifts out of sync from there. If I use the "Time Stretch" Effect to ensure that both the beginning and the end of the audio matches, it still drifts in the middle...

If anyone would like to play with the audio and video in question, you can download it here:

https://mega.nz/#F!oEMCVa5D!cibKfBweTCMP7NxseqlRFA

Airplane R1 Projector.wav is from somebody else's Elmo 16 CL projector.
Airplane R1.wav is from AEO Light (you will probably need to move it forward 26 frames for it to sync with the video)
Airplane R1v2.wav is from my Elmo 16 CL projector (and should be slightly better quality than the other projector)
Airplane R1 Preview.mkv is the video (plus audio from the first projector which I almost, but not quite managed to sync using the time stretch effect to stretch it by 100.908 %).

I'm hoping somebody can advise me on how to sync the audio from my projector (v2) to the video (which software to use and how to go about it) and/or how to get tbetter results from AEO Light. (Unfortunately, the video preview above does not include the soundtrack, but if you need a version that has it, let me know and I'll create a 10 minute sample for you to play with.)

yours hopefully,

Rob.
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#2
Hi Rob,

I often do fandubbing projects like this where the I'm using two different sources and I've never had much success with doing it based on waveforms. I follow this guide every time, it's time consuming but it hasn't let me down.

https://forum.fanres.com/thread-2776.html

Cheers
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Thanks given by: williarob
#3
The video file is flagged as "undecrypted" by Mega.
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Thanks given by: TomArrow
#4
I had a similar problem when capturing LDs
Video was captured with Blackmagic and the audio by QT7. When I did this, the audio was always going out of sync for some reason. The I dropped Blackmagic and only used QT7 for both. I had to cap the video in uncompressed, but the audio was staying in sync.
So my guess is that the audio should be captured with the audio in one app, to eliminate the syncing issue.
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#5
(2020-03-19, 07:43 PM)bendermac Wrote: I had a similar problem when capturing LDs
Video was captured with Blackmagic and the audio by QT7. When I did this, the audio was always going out of sync for some reason. The I dropped Blackmagic and only used QT7 for both. I had to cap the video in uncompressed, but the audio was staying in sync.
So my guess is that the audio should be captured with the audio in one app, to eliminate the syncing issue.

Unfortunately that isn't possible. The picture is coming from a USB camera at 10 frames per second and saved as a headerless .raw image sequence. Then the film reel is moved from the scanner to the projector where the audio out is used to capture the sound at 24 fps.
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#6
Here's an idea, but it would require some coding and tinkering: Record the 2 channels of audio output and simultaneously hook up some kind of electrical trigger to a third audio input and record that with it, so that for each frame there is a spike in the audio curve of the third channel. Then you could write a software that finds all those spikes and normalizes the speed (tho it would require some clever interpolation methods probably), and then it would just be a matter of syncing. Not a simple method, but it might be possible.

Alternatively, maybe there's some tool that can apply a speed curve to audio. Premiere for example can do that, but only for video afaik. What I think might be happening is that the speed changes as the load on the reels changes, similar to how cassette recorders will sometimes sound a bit different at the beginning of the tape than in the middle/end, at least if I recall that correctly.
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#7
I've ordered one of these:

http://www.moviestuff.tv/moviestuff_retr...odule.html

That should do the trick.
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#8
Sony Vegas Pro is the best for syncing audio. Currently i am using this software to sync Cinema DTS. you can shrink and stretch the audio without any quality loss or distortion in pitch.
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Thanks given by: williarob
#9
(2020-03-20, 03:26 AM)Soundman Wrote: Sony Vegas Pro is the best for syncing audio. Currently i am using this software to sync Cinema DTS. you can shrink and stretch the audio without any quality loss or distortion in pitch.

I think the distortion in pitch would be desirable though, because through the playback at wrong speed the pitch is already distorted. Syncing to the correct speed would merely bring it back to the normal pitch imo.
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#10
(2020-03-20, 10:39 AM)TomArrow Wrote:
(2020-03-20, 03:26 AM)Soundman Wrote: Sony Vegas Pro is the best for syncing audio. Currently i am using this software to sync Cinema DTS. you can shrink and stretch the audio without any quality loss or distortion in pitch.

I think the distortion in pitch would be desirable though, because through the playback at wrong speed the pitch is already distorted. Syncing to the correct speed would merely bring it back to the normal pitch imo.

Thank you Tom for bring this up, I wrote wrong about the pitch. "You can shrink and stretch the audio with distortion in pitch" Smile and that's what i am doing when i'm syncing the audio.

Keeping the pitch while stretching audio in Sony Vegas is pretty good actually, but you can always spot just a little bit anomalies in sound.
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