Audio Out o Sync (same frame rate)

[Motion]

- The jpg 2000 has 86428 frames with a play time of: 01:00:01:03
- The h264 mp4 has 86403 frames with the same play time: 01:00:01:03

[Carsten]

So, there is something wrong. '1:0:0:1" and for Video: 1:0:1:04' is a difference of 27 frames, slightly more than 1s. Is that the sync offset you hear/see?

Hmm, the difference between 24fps and 23.98fps over one hour creates a difference in runtime of about 4s.


- Carsten

[Motion]

Yes, I thought bout that possibility, but how if the AE project was 24 fps?

[carl]

How much is the sync out by at the end of the film?

[Motion]

more than 2 seconds

[Carsten]

I admit, without having first hand access to the media, I am out of options. This is not a typical issue. I would think that, when audio is not aligned/padded to the sample level, there may be minor deviations in playtime between audio and video. But that shouldn't produce audio gradually running out of sync.

What does this AfterFX project consist of? 1hr is a lot for a 'typical' AfterFX project?

- Carsten

[Motion]

I made a rough cut in Premiere, wich I exported to AE and made the rest there, from editing, graphics, color correction...etc...
The result was too big to export so I exported the video to jpg 2000 and the audio to wav.

To make an mp4 I ingest both audio and video to a new AE project wich now renders a lot faster and with great results.
To make a DCP I made the same procedure and the lag on the preview was only a few frames.
But then I updated DCP-O-Matic. I dont know If there was any relation.

Thanks!
- Motion

[Carsten]

I guess what I would do this to reopen the AfterFX project and add some audio sync cues (beeps/hits) to certain existing visual cues, in order to follow the sync issues developing. 3-4 sync cues over the course of the project should suffice. This also doesn't mess too much with that project - easy to remove them later.

Then create the DCP (don't forget to check 'Re-Encode'). Then play in a cinema. I wouldn't be so sure if DCP-o-matic audio/video playback sync is ALWAYS correct - the DCP MAY be okay, though. Do you use external sound hardware for playback?

- Carsten

[Motion]

I dont use external audio hardware.
I've tried a version with the Re-Encode option but no dice.

My only hope is there is some kind of lag in the video playback, but its strange though...

[Carsten]

The Re-Encode option does not fix sync issues in general. It is just necessary if you use J2K content from sources that do not follow DCI J2K constraints. SOME DCPs created that way without Re-Encoding had audio sync issues on real Cinema servers.

If you don't use special audio hardware, I guess neither DCP-o-matic nor the standalone player should exhibit/accumulate excessive delay in the range of 2-4s.

- Carsten