Decklink DUO a/v out of sync during preview

Hello,
I developed a simple directshow graph:

Decklink video capture(1) (1080i50) -> Avi decompressor -> video Render
Decklink audio capture(1) (2 ch) -> Default directsound device (clock)

My source is a video camera that outputs SDI signal with audio + video embedded.

Sometimes audio and video get out of sync into my preview graph.
CPU load is very low.

If I restart graph, audio and video become in sync.

Could it be because my decklink doesn't have a reference input?
Must source and decklink be syncronized with a reference input?

Thanks.
Davide

[Joshua Helling]

I'd recommend posting this to our Developer's list as this is more of that type of issue.

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