Why can’t PluralEyes sync camera footage with an audio recorder?

[Nigel O’neill]

[John Rofrano] “The crystals in these devices simply aren’t that accurate and yet I believe you if you say it’s working for you.”

I must be extremely lucky. Or the fact that I am using all Sony equipment 🙂

[John Rofrano]

How do you use WooWave from within Vegas Pro? I downloaded from a link that said, “click here to download version for Premiere Pro & Sony Vegas WINDOWS” but I don’t see it in Vegas Pro anywhere under the Edit, View, or Tools Extensions, nor in the Script Menu?

~jr

http://www.johnrofrano.com
http://www.vasst.com

[John Rofrano]

[Geoff Candy] “Just a long shot. PluralEyes comes as a standalone as well as plugin. Maybe the standalone version would work. I’ve tried a short piece shot with A1E Vid+Audio with independant picked up using a Zoom. Just followed a tutorial and it worked fine. Not tried it from the timeline yet.”

The problem is that I’m trying to fix drift. So I have one video file and one audio file and it takes me two seconds to sync them. Then after 15 – 20 minutes they drift and I have to split the audio and re-sync it. I was looking for a program that would allow me to split the audio every 5 or 10 minutes and sync it automatically for me. I need to to work on Timeline Events, not on individual files so I can’t use any standalone versions of anything. I don’t want to render individual files because I can sync them manually faster at that point.

~jr

http://www.johnrofrano.com
http://www.vasst.com

[Dave Haynie]

Assuming they’re using a real quartz crystal, and not some cheap-ass ceramic resonator (which is more like 0.1% to 1% accurate), the run-of-the-mill super cheap ($0.50) PC-class crystals have an accuracy of +/- 100ppm or better, and usually with only marginal temperature compensation at best. So that’s worst-case 0.01% accurate, or at 48KHz, that’s up to 17,280 samples per hour.. or a drift of about 1/3 second. Of course, if you have two of these running at the same time, you could actually be 2/3 of a second apart at the end of an hour (16 frames at 24fps, 40 frames at 60fps).

So in short, with cheap crystals, your WooWave is going to have potential trouble with clips over 1/2 hour. HOPEFULLY no one’s using cheap crystals like these. The super cheap ($0.50) 32kHz crystals used in PCs and other consumery devices for the TOD clock are usually around 30ppm.

I found a video of the Zoom H4 (older model) drifting 6-7 frames versus a Canon 7D over a ten minute shot… even given a frame rate of 30fps, that’s actually three times worse than my 100ppm worst-case. But the H4 and earlier Zoom recorders are known to have awful crystal stability, about 0.05%, or 500ppm — possibly even worse. Not sure about the 7D. Rumor has it the H4n has a clock accuracy of 50ppm; Zoom/Samson themselves say it’s accurate for shorter clips, and suggest software handles the issues in longer clips. Of course, they’re poised as the go-to field recorder for DSLR videographers, most of whom use Canon, and Canon’s still inflicting the EU’s issue with camcorder taxes on all of their DSLR users… so you can’t record more than 29’59” continuous on any Canon DSLR (many others go longer, but they’re a minority in the business). That would mean about 4 frames, worst case, at 24fps, with an equally reliable timebase in the camera.

I looked up the Marantz recorder John’s using, and several new ones, but there’s no indication anywhere of the timebase accuracy… so much for “professional”. Though the higher end unit, the PDM-671, has some kind of add-on for external sync. And it fixes a known problem with the pre-amps in the PDM-660, not sure what that is. I’m assuming the audio’s clear enough to be a good sync source.

For some of the digital radio stuff I’ve done over the few years, I use a 1.5ppm crystal as a timebase for the frequency synthesizer. This is a TCXO (Temperature Compensated Xtal Oscillator), too, so it’s pretty good over temperature. That’s going to mean 260 samples per hour, or a maximum device to device drift of 520 samples per hour… 10.8 microseconds. Not a practical problem in the least.. even good musicians can only hear about a millisecond of timing drift. But I had to pay a whole $15 each for those crystals (well, my company did).

-Dave

[Dave Haynie]

Derivatives of Mel-Frequency Cepstral Coefficients, or just the FFT, with cross-correlation? I had to solve a somewhat similar problem a few years back (software defined radio implementation of NTSC television, naturally had to run in realtime, had to reliably find the H/V syncs, also the color clock… FFT on that made it easy to find the phase offset). I had one decoder running on a single Intel Core 2 core, an MPEG-4 encoder on a second core… eight cores per rack. Kind of cool, and yet, a stupid way to avoid using a $2.50 chip 🙂 Using the SDR wasn’t my idea….

-Dave

[Igor Jovcevski]

WooWave is standalone. You select your clips in WooWave and sync. It creates folder with vegas edl files. Vegas support is EDL only. Try it out, and if you like it, you can ask me for a free license as I havent got many Vegas users.

Igor
Woowave.com
tools for digital artists

[Igor Jovcevski]

32ms precision is used in the first pass. There are three passes 🙂 for up to 96ms(losing precision to 3 frames) if there is no match in the main pass. In addition to this (Plural Eyes engineers , listen carefully 🙂 ),
Files are segmented and the drift becomes less of a problem. The only thing you lose is your ‘frame’ precision , which is not a big problem as all you need to do is trim few frames later on. and in addition to this, I am ‘blurring’ the patterns so the matches will be found even if you got terrible drift. you can try this with the sample footage on my site, it is ultra low quality , similar spectros as it’s similar music played. Plural eyes had big problem syncing it. Woowave managed to sync most of them, with one or two false positives only.

Igor
Woowave.com
tools for digital artists

[Stephen Mann]

[Nigel O'Neill] ” Or the fact that I am using all Sony equipment :-)”

Or that they buy all their crystals from the same source.

Steve Mann
MannMade Digital Video
http://www.mmdv.com

[Dave Haynie]

[Stephen Mann] “Or that they buy all their crystals from the same source.”

Unlikely. But I do believe that any camcorder company would understand the need for accurate timing, since pro video is always using multiple cameras that need to be synched. These things don’t always carry over between divisions, but even if not, it’s probably more natural for a Sony guy making a digital field recorder to think “video”, given that Sony IS one of the big four in pro camcorders, compared to the guy at Samson making the first Zoom recorder. The Zoom guys DID get the message, as my more detailed discussion above points out.

Yeah, it CAN be luck, between two devices. Once you have three or four that remain in sync, and it’s NOT by design… well, if you’re that lucky, I hope you bought a PowerBall ticket last night 🙂

-Dave

[Stephen Mann]

What is the main function of the “Audio Recorder”? Is it advertised as a voice recorder? Voice recorders are notoriously bad with timing and hardly ever sync with video.

Steve Mann
MannMade Digital Video
http://www.mmdv.com