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This topic comprises 2 pages: 1 2
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Topic: Equipment for adjusting A/V sync
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Carsten Kurz
Film God
Posts: 4340
From: Cologne, NRW, Germany
Registered: Aug 2009
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posted 01-01-2017 10:05 AM
Well you could use all sorts of gear to check AV sync. As today's Smartphones can do so many things, I'd always prefer an app that can solve a problem practically with the needed accuracy over dedicated high precision gear. Simply because I always have it with me. The good and practical thing about catchin' sync is that you can check sync right on the site and at your/the viewer position, and it gives the proper readings in ms, which we need for corrections in typical installations. I used to take videos in 50p with my camera before, but needed to analyse them later on a PC to get a number.
For what it does, it does seem a bit expensive compared to other basic apps, but the company makes Pro Audio Tools and considers Audio Pros to be their clients, so what...
The free version only supports 25 fps, which is usually okay for the occasional check of your server or CP. The good thing about this app turning visual readings into numbers is, it is quite flexible about the calibration video, so you can easily make your own with e.g. added check for surround channels. It's also not spoiled by 3D formats. The capability to use your own sync videos/sources also means that you can check full capture and processing chains, e.g. from your camera through your video editor and monitoring system up to the final presentation, be it DCP, DVD/Bluray, MP4, some mediaplayer, scaler, etc.
With recent iPhone models, you can easily reach subframe accuracy.
- Carsten
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Jim Cassedy
Phenomenal Film Handler
Posts: 1661
From: San Francisco, CA
Registered: Dec 2006
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posted 01-01-2017 07:11 PM
The app you mention is for measuring sync delay.
Most cinema audio processors have settings where you can adjust the delay.
For example, on the CP750, you can do 'global' delay settings for main
and surround audio, as well as customized delay settings for each input.
I work at both of Dolby's private screening rooms here in San Francisco.
As Scott mentioned a few posts back, there are, for whatever reasons,
sometimes DCP's with sync that's a frame or two off. I was a professional
1" videotape editor, so I tend to notice even tiny sync errors, as do
many of the audiences I deal with at Dolby since they're often made up
of film-makers, editors, and other media-tech professionals.
If something looks off-sync at Dolby, they a have a couple of "Syncheck"
units.(Synchceck II and a Syncheck III)
To use them, we play a specific sync-check file on the server, which is
basically just a repeating "pip-flash". You stand in the auditorium
and point the syncheck unit at the screen and it can tell you, using
either a row of LED's (Syncheck II) or a digital readout (Syncheck III)
exactly how many frames or milliseconds your system delay is "off" by.
Of course this does nothing to 'fix' badly synched DCP's, but it does
allow us to verify to a filmmaker that our system is "on spec" and
that the problem is with either the DCP editing or mastering process.
Of course, once I know the amount of delay error, I can dial a correction
into one of the I-pads that control the audio delay system, and make
the sound come out in sync. I've had to do this to "save" a couple of
screenings that would have otherwise been noticably out-of-synch.
Unfortunately, the Syncheck units are no longer made, or I would have
bought one for myself by now. They weren't that expensive, only a
couple of hundred bux, if I recall. Maybe someday I'll find a used
one on e-bay, or perhaps Dolby will want to get rid of one of theirs.
If your curious, you can see the old Syncheck website--> HERE
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