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After Effects and DNxHD bit rates?

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Derek MinerAfter Effects and DNxHD bit rates?
by on Nov 1, 2013 at 1:59:13 pm

Graphic designers at the office where I work are rendering clips out of After Effects (5.5) for Avid Media Composer, so they are using the DNxHD codec.

I've seen a designer select the correct format at DNxHD 220 but the resulting render has a large file size and a bit rate in the 700 range.

Can anyone shed some light on this behavior or any potential flaws in the workflow that is being used?

= Derek Miner =

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John CuevasRe: After Effects and DNxHD bit rates?
by on Nov 1, 2013 at 2:43:26 pm

DNxHD has large files(not like uncompressed AVI or Animation QT). If you are working in Avid though, it's really the way to go. If you are set up correctly you will get Fast Imports(no transcoding) and it looks great. 220 is one of the higher rates of DNxHD, and as our workflow developed with DNxHD, we've never used it. Mostly it's just a space issue vs the increased quality doesn't seem worth it.

Perhaps if we were doing film work, we might want that 10bit, but if at our house we just stick to the lower quality 8bit modes and they seem to work just fine. You might want to do a couple of tests.

I don't see any flaws in your workflow.

Johnny Cuevas, Editor

"I have not failed 700 times. I have succeeded in proving that those 700 ways will not work. When I have eliminated the ways that will not work, I will find the way that will work."
---THOMAS EDISON on inventing the light bulb.

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Derek MinerRe: After Effects and DNxHD bit rates?
by on Nov 1, 2013 at 3:04:06 pm

Thanks, Johnny,

I should be a little more specific about why the files I'm seeing are concerning me. The DNxHD clips I get from After Effects are around three or four times as large as if an editor exported a clip from Avid in DNxHD. MediaInfo is reporting bit rates in the 700s instead of what I'd expect from the bit rate specified in the codec settings inside After Effects.

= Derek Miner =

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Jon BaggeRe: After Effects and DNxHD bit rates?
by on Dec 6, 2013 at 2:59:02 am

Does it contain an alpha channel? If it does and the alpha channel is set to 'uncompressed' it will massively increase the size of your file beyond the normal DNxHD bitrate. Switching to 'compressed' will make it only slightly larger.

You can change compressed/uncompressed alpha channel within the DNxHD dialogue box when you change render output settings.

Jon Bagge - Editor - London, UK
Avid - FCP - After Effects

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