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#1
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Video sync stability
I've been doing some tests with audio/video sync, much in same way the Syncheck used to work - 1 frame of 1kHz tone concurrent with 1fr white flashes on a video screen.
I'm running my video output, via a Blackmagic PCI card in a Thunderbay expansion crate, and then via HDMI to a domestic grade Toshiba LCD screen. I've started from an H264 (created for me by a video editor) and have placed audio sync pips on a mono PT track. The results I'm getting are quite variable: with flashes/pips every 2 seconds the measured sync can vary by about a frame (max to min). I'm interested to know whether there is something inherrently unstable about my PT and video hardware, whether the H264 is the weak link or whether it's my measurement ... or whether that's reasonably stable. Any thoughts?
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PT2020.5.0 / HDN / HD Omni / MC Control / Intensity Pro / Catalina / 3.7 Quad core Intel Xeon ES (trashcan) MacPro / 12GB RAM Over 30yrs experience in pro-audio - mostly for picture. |
#2
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Re: Video sync stability
H264 is most definitely your weakest link. Try testing with DNXHD or ProRes
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#3
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Re: Video sync stability
Quote:
See here: https://www.pro-tools-expert.com/pro...ools-explained (BTW: the illustration in that article is missing an important connection: the sync signal going to the video hardware from the generator. Without it it won't work) But with your hardware you won't be able to achieve 100% sync so you'll have to live with up to +- 1 frame of sync span for every time you hit play.
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PTHDn 2024.3 (OSX13.6.5), 8x8x8, MacPro 14,8, AJA LHi, SYNC HD, all genlocked via AJA GEN10, 64GB RAM, Xilica Neutrino, Meyersound Acheron |
#4
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Re: Video sync stability
Hi Idris,
If you have an iPhone you can use Catchin' Sync to test your system lag. |
#5
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Re: Video sync stability
I frankly still don't understand why people continue intentionally hurt themselves?
Its been said and written and white papered on every corner: use DNxHD36 or ProRes Proxy for most reliable sync. An H.264 is a quick delivery codec and is NOT suited for work with Pro Tools. Its nature makes it drifting in unpredictable way even when trying to use it within the proper genlocked system.
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Michael Goorevich Sound Designer / mixer www.goorevich.com PT HD⎪N v2024.3 Ultimate ● macOS Ventura 13.6.3 MacPro 7.1 (2019) 3.2GHz Intel Xeon W 16-Core ● 96 GB RAM MTRX Studio + DADman 5.7.0.1 + MOM ● Sync HD ● AJA Kona LHi referenced by AJA GEN10 ● D-Command ES24 |
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