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View Full Version : Audio Drift playing 4K 23.98 out of Scratch



JD Marlow
05-04-2009, 01:32 PM
Hi all,

Playing out 4K HD (3840x2160) R3D media out of Scratch w/ 2 channels of embedded audio to HDCAM-SR 1080p, 23.98. Using the lowest resolution @ 1/4 res Medium.

The audio was recorded from an external device and jammed into the RED camera -- so there is a 3 frame delay on that as it is. When played back on the construct with no slip the audio is 3 frames out of sync.

However, with a slip on, when playing out to tape the audio drifts slowly out of sync. It is a 20 minute long interview clip with no timecode breaks.

I have confirmed that the audio was recorded correctly -- it stays in sync when played down on the construct. But when going to tape the drifting occurs. Any ideas what could be wrong? We are running the Beta version of Build 528.

Lucas Wilson
05-04-2009, 03:10 PM
Hi all,

Playing out 4K HD (3840x2160) R3D media out of Scratch w/ 2 channels of embedded audio to HDCAM-SR 1080p, 23.98. Using the lowest resolution @ 1/4 res Medium.

The audio was recorded from an external device and jammed into the RED camera -- so there is a 3 frame delay on that as it is. When played back on the construct with no slip the audio is 3 frames out of sync.

However, with a slip on, when playing out to tape the audio drifts slowly out of sync. It is a 20 minute long interview clip with no timecode breaks.

I have confirmed that the audio was recorded correctly -- it stays in sync when played down on the construct. But when going to tape the drifting occurs. Any ideas what could be wrong? We are running the Beta version of Build 528.

Hey JD,

This is deeefffffinitely a question for internal SCRATCH support. Please contact Support and let us help you! By the way - 528 is no longer Beta - it is the 4.3 Release.

This is probably one of two things - either a 23.98/24 mismatch, or a sync issue with audio and video cards not being properly synced.

Lucas
------
ASSIMILATE, inc.
LA, CA, USA

JD Marlow
05-04-2009, 08:04 PM
Very strange indeed Lucas --- we decided to try and "post-sync" the audio by taking it out of the R3D proxy files and doing an insert edit from Final Cut Pro

It still drifts! We're trying a few other things in the mean time, but this is very curious. Makes me think the audio was recorded at an incorrect sampling rate and / or frame rate.

Any opinions? Our folks might be reaching out to you depending on what we end up finding...

Frank Cueto
06-18-2009, 06:51 AM
Do remember that 23.98 is non-existing. Are you forcing it to do 23.98 or are you actually doing 23.976?

-Frank