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SD to SD conversion - loses sync

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cmlundy
SD to SD conversion - loses sync
on Mar 21, 2007 at 5:19:21 pm

I have setup a sequence at Anamorphic 16x9 in Final Cut. Instead of going out anamorphic to Digibeta we need to get the client a letterboxed version. No problem, use the Kona 3 SD to SD conversion and choose letterbox. Looks great, seems fine. Here's the rub.

When we output the sequence we notice the audio is early by 1 frame (or conversely the video is late by 1 frame). In other words, we have Leader at the top of the sequence with countdown and 2-pop. When I output straight away as anamorphic the 2-pop's video and audio are dead on. When I go letterbox via the Kona the 2-pop's audio and video no longer hit at the same frame. I've been told by AJA in the past that conversions via the card often require "giving up a frame" as it was put. Anybody seen this behavior or developed a workaround? My only thought would be to deliberately put my sequence out of sync by a frame and expect the delay to put it back in sync. This is with SDI video and audio by the way.

Any help appreciated.



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JeremyG
Re: SD to SD conversion - loses sync
on Mar 22, 2007 at 3:38:35 am

[cmlundy] " My only thought would be to deliberately put my sequence out of sync by a frame and expect the delay to put it back in sync"

Looks like you have found your answer. It takes time to process video and your audio must reflect that time.





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cmlundy
Re: SD to SD conversion - loses sync
on Mar 22, 2007 at 1:32:56 pm

Fair enough. But if that's the case it should be clearly stated in the manuals as it is for other products that process video, such as the Teranex. And if it's going to slow my video down it should go ahead and delay the audio for me too so I don't have to workaround it. Little things like that go a long way. The card does some great things, many of which the Avid Adrenaline BOB won't do, but they need to make it clear what you need to do to get certain things to work as expected. I work at a facility where we get so many different combinations of things thrown at us so maybe I'm seeing the card in more varied scenarios.

If anybody has any other thoughts on this or has seen these processing delays I would appreciate your thoughts.


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JeremyG
Re: SD to SD conversion - loses sync
on Mar 22, 2007 at 2:43:00 pm

You should then write support@aja.com and make a feature request to put that info in the manual. I am sure that feedback like that is probably exactly the sort of thing they'd want to hear.

Also, problems like these are very common. Have you done anything in 23.98 with a Varicam? There's some sync issues there that have nothing to do with AJA. It's inherent to video and all the crazy formats we have to deal with these days.

Good luck.

Jeremy


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