Realtime v. iPad time

[MIDI Life Crisis]

When I record simultaneously to DP and video on my iPad Pro, the audio from the iPad doesn't stay in sync with the file in DP. IOW, the iPad audio, which matches the picture, is slightly faster than the audio that DP records. My best guess is that the iPad is compressing both audio and video slightly. Not enough for normal humans to perceive, but the computer doesn't lie. Or does it?

Example: today I recorded a 30 minute performance to picture on the iPad. Simultaneously, I recorded audio with the piano mic'ed. When I went to use the audio from DP in Final Cut Pro, the sync was off by a little less than half a second by the end. So the final chord is heard in DP before the visual of me actually striking the chord appress onscreen.

Of course, with most things, there is a workaround and now that DP is better at stretch (at least in small increments like that) I can just stretch the DP audio and visually match it to the imported audio from the iPad, but I am curious if anyone knows what's going on here?

Mike Halloran? MagidD? Stubby? Monkey Man? Timeline? ANYONE?

Thanks.

MLC

[stubbsonic]

I'm not at all qualified to answer, but I'm happy to muse on it.

Because your iPad isn't clock-synced to your computer, that amount of drift is to be expected. It's complicated to try to get clock from the iPad (via an interface with a digital clock source) to the computer (with a digital clock input). You'd at least need both interfaces to have spdif or optical i/o, something to sync to. Not worth it, IMHO.

I wonder if there's a way you could force FCP to change the frame rate of the video, but since you're only talking about maybe 15 frames over 30 minutes, that might be a pretty fine adjustment. Maybe there are tricks for fixing the video that don't involve messing with continuity (adding frames).

[MIDI Life Crisis]

I just checked the video from the ipad to the video from the original film and it's also off by about 15 frames. Maybe a little less. Not enough to worry about for old silent films. This stuff will broadcast over Facebook next weekend on Friday and saturday at 1pm Pacific.

https://www.catalinamuseum.org

Here's a little I promo I produced for them:

http://www.midilifecrisis.com/misc_imag ... _Final.mp4