A tech in for a recent tech check used a device to check AV sync picking up the flash frame and the simultaneous beep and calculating any difference. Seems like this could be done with a smartphone app. What are you using?
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Seems to be pretty much the standard. Not really cheap, but does the job and produces consistent results. -
I haven't tested this app, but it's free, so, try it yourself:
Last edited by Carsten Kurz; 07-03-2025, 09:56 AM.Comment
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"Catchn' Sync" is also a popular app based one.
iOS Catchn' Sync
But all phone based solutions are a bit cumbersome because the developer has to account for the in phone delays (and it's different for every model), and delays changing between OS versions, so besides telling it your model, they usually encourage an initial calibration routine you do with a zero delay source, such as a clap/clapper etc. But any adjustment is a one time setting. SynQR may not and just rely on it's device database.
SynQR seems a bit more polished, but claims "in app purchases", so maybe not free. Neither is the full version of Catchn'Sync. SynQR seems to want a custom piece of content played with the QR codes. The advantage of CatchnSync's method, though less polished, is you can do it with any old test or framing DCP that has a sync reference (as most Disney framing charts do etc). SynQR also doesn't support some older devices (like the 6th gen iPad I just tried to install it on).Last edited by Ryan Gallagher; 07-03-2025, 10:56 AM.Comment
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I would have to look it up later, but afair it was around 400€ including shipping/customs.Comment
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sync-one2 is what the tech had. In theory we are now dead-on for DCP but I'd be curious what the meter would say about DVD / BD or Roku not that this comes up professionally much or at all for the latter. But not worth putting money into.Comment
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The USL/QSC LSS-200 would also do A/V sync check. On phone applications, it seems that there should be a user calibration setting where you clap your hands (or get a film clapper board) in front of the camera and set that to zero (or about 1 ms/foot ). You would not care about sync issues in the phone itself.Comment
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you could always take a high frame rate video, drop into a free video tool and count the frame between the flash and the beep, as a rough estimate.Comment
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I thought about that. If I apply the audio to a scope screen the video alone can capture both without any concern of sync errors in the test video. And with a dual trace scope and a solar cell it can all be on the scope screen. A real CRT scope.Comment
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How perfect is needed? I take a slow motion phone video of the screen with a sync check cpl, on playback I can see the offset to adjust the delay pretty easily.Comment
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For several years I did a fair amount of freelancing at a number of local and several national
film festivals (and I'm still able to take time off from my regular job to work festivals a couple of
times a year) I had gotten myself one of the Sync-One-Two devices after getting used to using
one at Dolby. It has saved a lot of time arguing with both professional and not-so-professional
filmmakers at some of these events. Also good for checking audio delay at unfamiliar venues,
although most of the big fests I've worked at have professional audio techs to do that. (and a
few of those techs have even borrowed my device, if they didn't already have one, to prove to
someone that audio sync is OK. It's hard for someone to argue when you can stick actual
numbers in front of their face) I ordered mine online through 'Scenic Labs' in New Jersey,
since they were the only ones who had one in stock at the time wanted to get one. I just
looked up the bill, and I paid $395us. (Just for fun, I've also pointed it out my window
during a lightning storm to measure the thunder delay. )lol
SyncOneTwo.jpgComment
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A correction: That's not what the tech was using but he was using their video which he converted to DCP.Comment
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There was/is an app for the iPhone (or maybe iOS) called "Catchin' Sync" that allowed one to calibrate their phone (since there may be latency there). So, you take a book or a clapper and first record that. Find what your phone's offset is and calibrate it for dead-sync. Then you can use any DCP content for verifying since since you get an audio waveform as well as the picture. All you have to do is sync them up and it reveals the time disparity.
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