Have been cutting a 5-camera multicam concert in NTSC (I've got very little NTSC experience). It's been going fine generally, but I'm having playback issues with the audio.

I have the whole concert in sync with the mixed audio I've been given - no problem, go to anywhere in the timeline and it's all fine. But if I let it play for 30 seconds or more then quite suddenly the pitch and speed of the audio will jump noticably (not always a consistient amount). And the more it plays the more out of sync the audio and video become (audio leads video by more and more as the playback continues).

If I hit stop and start again then it's all fine, the audio is in sync with the pictures, until it shifts pitch/speed again.

The audio project is 48kHz, and the mixed AIF file is also. I've checked to confirm that it has also imported as such, which it has.

All media exists on a single FW800 drive at DV25 (was shot with DVX and PD150 cameras). The mixed audio was imported from a Data CD where it was AIF 48k/16bit Stereo.

Media Composer 3.0, XP SP2, HP XW8200 w/4GB

It's not the worst thing in the world, I've managed to work with it, but it just means I can't do a playout or anytyhing (not that I have a deck that can record NTSC anyway). But it's annoying as I can't watch the project end to end uninterupted.

 Dylan:

We had this very same issue with four of our Adrenaline suites, minus the pitch change. Ultimately, the solution was to re-do the external sync reference signal flow to eliminate all looping of sync signals and using distribution amps to distribute individual, properly terminated gen lock feeds to each component separately. Afterwards, all of our lip sync drift issues just disappeared.

Hope this helps you.

Not really in this case unfortunately Larry, as we have no NTSC hardware at all we're basically rolling 'Software Only' on this, genlock not really an issue or option.

Thing is it's not drifting - If I start playing at the beginning it's dead on. Skip to the end it's great. Anywhere in the middle, fine, but if I start playing from anywhere and let it play for more than 30 seconds or so uninterupted, then suddenly the pitch jumps up and it starts getting ahead of the video. Double-tap the space bar and we're off again, right as rain.

Very odd.

I exported a QT reference and made a DVD with it (needed to give to client anyway) and it was fine all the way through. Just some weird thing where it is playing the audio back at a faster rate. I want to blame NTSC because I don't use it, but a collegue insists the same thing happened to him on a PAL project.

How many hard drives are you using and how full are they? I've heard of (and have had) similar problems in the past when drives get around 90% full. Can you delete any old projects from the drive(s)?

 If it's a software only system (no I/O DNA box), I'd start thinking project corruption.  Have you tried deleting the project setting files?

Full drive and project corruption are both realistic possabilities I reckon.

I'm not in the office today or tomorrow, so I can't check at the moment, but I'll check it out later.