Sync problem - I'm going crazy

[VictorA]

Hello everybody.

First, sorry for my english...
Second: I have a big problem with sync for a DCP I try to make. It's a 25 fps stereo master and I convert in 25 fps with a 5.1 mix B in DCP o MATIC.
Everything is fine excepte a little shift between sound and video. Its a Live concert video and its particular clear for the drum, often its not sync... But Its crazy because when I read the DCP on my computer the Sync is OK. The master and the DCP its sync good when I read it on my computer but in theater there is a little audio shift. Tomorow I will try the DCP without automatic 5.1 mix from DCP O MATIC but do you have any ideas of whats wrong ?? It can be a Audio delay pb ?

Thx so much for you help!

Victor

[Carsten]

Do the test with a stereo DCP first.

- Carsten

[VictorA]

I think I find the problem... If I read the DCP on my computer with DOREMI cineplayer I have the same sync pb than the theater. If I read the DCP with stereoscopic player sync is OK . So I put a -180 ms audio delay in DCP O Matic and with DOREMI cine player the sync is good. So I will run to the theater for test!

Anybody can explain to me what happened ?!

Thx

[VictorA]

SO... The DCP is sync in the theater with -180 ms audio delay setting in DOM. I read somewhere there is a offset sync in theater for help with latence. But do you think this offset sync can change in different theater ? Or its the same value in all theater ? If its the case why DCP o matic don't put a automatic audio delay ?

Thx for you help

[Carsten]

I have no explanation for your experience. DCPs are made to '0-offset'. All necessary delays are configured in the theater cinema audio chain, either server side, or by the cinema audio processor.

If you input 0-offset source footage into DCP-o-matic and leave the delay offset at 0, your DCP will be formally correct.

Sometimes non-standard DCPs or bad server software may introduce delays at playtime.

If your DCP with a baked in delay plays in sync at that theater and they are using their standard audio configuration, all commercial trailers and features there should show an inacceptable sync offset. I can only assume your source footage contains an inherent sync offset, or that DCP-o-matic has trouble decoding it properly. Or, it MAY be a problem with DOMs 5.1-upmixer. Did you try the plain stereo version?



- Carsten

[VictorA]

Thx Carsten.

I just realize its the theater have sync probleme. For all the movie !
I try a stereo version of the DCP and its the same pb...
But its weird because when I use DOREMI cinema player in my computer the DCP is out of sync like in my theater ... If I use NEO dcp player no sync probleme ...

[Carsten]

On a typical PC, there is no hard sync relationship between audio and video. It depends on your audio and video hardware (even your monitor) and drivers.


DCI servers implement a hard sync method. What you experience with Doremi and Neo DCP player is just random or machine specific. The software players need a configurable audio/video delay option to cope with that.

- Carsten

[flaprise]

I made a DCP and audio and video aren't sync.
Audio is a little bit later and seems to be a regular delay.
The master is ok.
It's 23.976 converted to 24.
Using version 2.14.51

Any idea?
Thanks a lot!

Francoise

[Carsten]

Is the audio in separate files, or is it an interleaved video+audio file?

Can you upload the metadata.xml from that project here?