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Decklink 4k Extreme capture to prores HQ bit rate issues

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Ian Lamb
Decklink 4k Extreme capture to prores HQ bit rate issues
on Dec 11, 2014 at 12:18:47 am

I'm capturing SR tape at 1080p 23.98 to ProRes HQ for delivery. We recently swapped out our AJA Kona 3 for a new decklink 4k extreme so I'm a little new to using black magic hardware and software. Apologies if this is something simple I've missed.

The issue is that the ProRes created by BlackMagic Media Express is a constant bit rate (which I thought was impossible) vs the quick times we created with the AJA card installed that were showing as variable bit rate.

This results in delivery files that are much larger than the files my client is used to getting for around the same duration.

There is also an issue of 8 channels of audio being grouped into one while with the AJA card the 8 channels would be discrete and individually editable in quicktime pro… I'm more concerned about the bit rate issues however.

Any help would be greatly appreciated!

thanks,

-Ian


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Chad Pearson
Re: Decklink 4k Extreme capture to prores HQ bit rate issues
on Dec 11, 2014 at 1:23:52 am

I believe Media Express only does constant bitrate recording, though it is dependant on the QuickTime library for capturing in ProRes. Have you tried capturing in QuickTime Pro directly instead of Media Express? Or in an NLE for example?


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Ian Lamb
Re: Decklink 4k Extreme capture to prores HQ bit rate issues
on Dec 11, 2014 at 1:59:37 am

Great idea, thanks! I dusted off FCP7 and had to roll the black magic drivers back to version 9.9.2 but FCP indeed captures variable bit rate through the decklink card. I'll try Premiere CC next as flipping drivers back and forth all day will slow things down considerably.

Really missing AJA VTR control right about now.

Thanks again!


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