pix240 + F3 + 788T timecode sync

[Michael Gissing]

Yes. There is a delay from the F3 to the PIX so external audio on the same master clock will be ahead by 2 frames. I am working on a project with the same workflow and the guide audio was being radioed back to the PIX. It was discovered after the shoot was over that there is an option to delay the audio to compensate but this doesn’t alter the sep sound files from the 788t.

So the answer is to feed the audio through the camera which keeps both the ProRes and XDCam files with sync guide. Hopefully you do not need the XDCam files so if audio needs to be resynced from the 788t, the 2 frame offset needs to be done. In my case I can manipulate the EDL by 2 frames from the cut to do the reconform in Fairlight.

My preferred workflow is to use one camera as time of day timecode master not the 788t unless you have a master video clock from the camera. Otherwise the timecode feed to the cameras will not be correctly frame synced. A much better setup is to jam the 788t from the master camera. I will check my 788t and see if it is possible to jam with a 2 frame offset which would fix the sync issue as well. By momentary jamming the 788t twice a day you can untether as well. On a three week shot we had complete sync lock and no drift that way (apart from the 2 frame offset). I hope at least one shot in the whole production had a clapper so you can do a sync test. Should be part of every camera test.

[Paul Isaacs]

Hi Olivier,

Yes, Michael is correct. The F3 HD-SDI video output is delayed. You can compensate for this either in the PIX or 788T depending on which one you’re using to record audio. Both PIX and 788T have audio input delay settings. Try setting for approx 2 frames (approx 66ms for 30fps).

Also, for better sync, consider using the PIX as master for both genlock and timecode (PIX has a built-in Ambient Lockit TC and sync generator).
Decide which PIX you want to be master then jam the other PIX and 788T to this. Since the PIXs and the 788T have ultra low drift and finely calibrated clocks, they will run very tightly in sync all day.

Then hook up each PIX’s timecode output and sync output to each F3. Set each camera to sync to its genlock input and ext TC input. Set the PIX’s sync (genlock) out to the required tri-level sync signal type to match the camera’s frame size and frame rate. Now both F3’s will be tightly synced to each other because they are being clocked by the ultra-stable, calibrated PIXs that are attached to them.

This setup should produce excellent sync results with zero TC offset and ultra low drift. You shouldn’t even have to re-jam during the day.

Paul Isaacs
Technical Development Manager
Sound Devices LLC

[Olivier Aubut]

Thanks Michael for your input. Glad to hear i’m not crazy.

If I understand correctly, you’re not using Wave files created by the 788t, you’re using the audio recorded on the Pix from the 788t. I need the wave files and the ProRes to be in sync.
We’re on shooting day 5 of 31, so the sooner we can fix this, the better.

Paul: Both cameras sync together correctly, it’s the Prores files that do not match the Wav files.
I’m being told by the sound guy that the 788t has a maximum delay of 30ms (in 23.98fps).

Thanks guys
Olivier

[Paul Isaacs]

Hi Olivier,

Have you tried using Multiclip Offsetter from:-
https://davidheidelberger.com/software.php

This takes a group of Quicktime movies, looks at the timecode track, and duplicates it into a new Final Cut Pro readable AuxTC1 track based but offset by a user-supplied number of frames.

Seems to work. This is probably the easiest way to correct the offset created by the camera.
The ideal solution would be for Sony to get rid of the delay on their F3 SDI outputs. That, I guess is unlikely to happen anytime soon. In the meantime, Multiclip Offsetter seems to work.

best

Paul

[Olivier Aubut]

Thank you Paul
that’s exactly what I was looking for.

Have you been able to successfully process files created by the pix? I get an error message telling me the app needs to quit (with Apple ProRes 422 1080@23.98).

XDcam quicktimes seem to work fine though.

Olivier

[Paul Isaacs]

Yep – no problem importing and playing back 1080p23.98 ProRes422 files in FCP7.

Paul

[Olivier Aubut]

No, I mean Multiclip Offsetter is crashing on files created by the Pix240.

[Paul Isaacs]

Seems like Multiclip Offsetter is not compatible with Quicktime files that include audio tracks as well as a video track
If you set the Pix240 to not record audio (by turning audio input off), then MultiClip Offsetter will read the files fine.

Paul

[Olivier Aubut]

Interesting.

Will try it out.

Thank you Paul.

Olivier

[Michael Gissing]

Paul can the 788t do a momentary jam using the PIX as master but jam with the two frames offset. That way the sep audio will sync without problems with the F3 delayed pics.

I know it is possible to do this as I used to jam with offset in an old ADx timecode generator last century.