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Variable frame-rate/dropped frame captures

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Stuart Trevor
Variable frame-rate/dropped frame captures
on Jan 16, 2007 at 4:17:20 pm

Hi,

I'm looking for a solution for capturing from a source where constant frame rate can't always be guaranteed, via a Xena card, and ending up with a solid capture at 720 30p. Unless the card can do some magic to the HD-SDI stream en-route and off the shelf (I'm very doubtful but it sounds vaguely similar to how VariCam captures are handled) I'm thinking it'll need post processing and/or the availablity of a SDK for the card, similar to Blackmagic, so we can write a custom capture app to our requirements. Then it would maybe ignore duplicate frames automatically during capture (which would be absolutely ideal) or insert silence/markers/metadata to mark drop-out so the stream could be processed post capture to remove any offending sections. We could also capture at a rate that can always be guaranteed, maybe 20fps, but only capturing 20 * 1/30th sec audio a second and stringing this with the video back into a constant 30fps stream - not sure if this is possible at all though, I guess it'd depend on the innards of the SDI standard.

Just wondering what your thoughts at AJA are on this - my hunch is it'll either be very simple or (likely) very complicated, it's a non-standard problem but something I need to find a reasonable solution to.

Thanks in advance,
Stuart


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AJA Xena Support
Re: Variable frame-rate/dropped frame captures
on Jan 16, 2007 at 4:56:17 pm

Stuart,

As long as your SDI stream has active frame flags in it, you will be able to capture Varicam. The capture will contain all the audio with only the active frames.

AJA Xena Support



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Stuart Trevor
Re: Variable frame-rate/dropped frame captures
on Jan 16, 2007 at 5:04:12 pm

Hi,

Thanks for the reply - I've never had any experience of working with Varicam so hadn't heard of active-frame flags - if this method would enable a Xena 2k to handle a dynamically changing input it might be exactly what I'm looking for. I'm off to cross my fingers and do some reading.

Thanks again,
Stuart


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