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4:2:2 chroma subsampling, PCM audio, and 24-bit audio sample size - can I output these from After Effects?

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Mike Imam
4:2:2 chroma subsampling, PCM audio, and 24-bit audio sample size - can I output these from After Effects?
on Apr 27, 2011 at 6:41:09 pm

HI all,

New poster here at the Cow, but I've long relied on the helpful community here for answers to tons of my AE questions. This one is pretty specific though...

I'm preparing a video for potential broadcast submission, and I am up to speed with all the specs they are requesting, with the exception of the following:

- The specs call for "4:2:2 chroma subsampling". No idea what chroma subsampling is, but I couldn't find this term anywhere in the AE help files. Any idea if I can output to this format? If so, where do I set this?

- They ask for the audio codec to be PCM. I don't have PCM anywhere in my audio render settings - any idea why not? Or is "uncompressed" (which DOES appear as an option) the exact same thing?

- They want my audio sample size to be in 24-bit format. Again, in my render settings, I only have the choices of 8-bit, 16-bit, and 32-bit. Am I doing something wrong? An an FYI, I'm using an MP3 in my timeline - not sure if this matters.

Few other key pieces of info: I'm using After Effects CS5, format of the video is Quicktime in ProRes 422 (HQ) format, 1920 x 1080.

Hopefully someone can help shed some light!

Thanks
Mike


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Dave LaRonde
Re: 4:2:2 chroma subsampling, PCM audio, and 24-bit audio sample size - can I output these from After Effects?
on Apr 27, 2011 at 6:52:52 pm

[Mike Imam] "...the video is Quicktime in ProRes 422 (HQ) format, 1920 x 1080..."

Sorry to be the bearer of bad news, but if this video was shot on XDCam, HDV or a DSLR and converted to ProRes HQ, it has already lost the primary virtue of 4:2:2, which is better resolution in color information. The video was recorded that way, and there's no way to bring it back.

By rendering in ProRes, you'll still be able to claim that you preserved all the 4:2:2 chroma subsampling you could. If you render the audio as uncompressed in 32-bit, you'll be fine. You didn't mention the sample rate: is it supposed to be 48kHz? 44.1 kHz? Something else?

Fiunally, never NEVER use mp3 files in AE. Convert them to aiff or wav first. AE has NEVER played nicely with mp3's, and it doesn't now.

I should also mention that the last time I rendered audio & video together was about five years ago... or was it longer? I only use audio for reference, and I render video-only, even on lip-sync stuff. I marry audio & video together in my editing application, with no problems at all... and from there I can make whatever kind of audio I need. AE's audio capabilities are limited at best.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Mike Imam
Re: 4:2:2 chroma subsampling, PCM audio, and 24-bit audio sample size - can I output these from After Effects?
on Apr 27, 2011 at 7:09:16 pm

Thanks Dave - appreciate the help. I failed to mention that this is an animated music video, so it wasn't using shot footage at all (did 100% of the animation in AE itself using Illustrator graphics). In this case, I assume the 4:2:2 chroma subsampling is done by default once I export? Could you briefly explain what exactly this is, so I'll understand it better once I do export from shot footage? I use my Canon T2i as a primary camera, so should I not be converting these to ProRes for RTE in Final Cut (bit off topic) as I'll lose this information?

My audio sample rate should be 48kHz, wich is fine (it's an option).

Thanks for the tip on MP3s in AE. I find my workflow to be easier when I don't have to export my music videos from AE then export again from Final Cut, so I'll often just throw my audio track in AE itself.


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Michael Szalapski
Re: 4:2:2 chroma subsampling, PCM audio, and 24-bit audio sample size - can I output these from After Effects?
on Apr 27, 2011 at 7:25:08 pm

Even if I don't use an NLE after I export from After Effects, I never use AE for my final output.
I render a lossless file from AE and then use the Adobe Media Encoder for any compression. Some people use Quicktime Pro, Sorensen Squeeze or other dedicated compression applications.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Walter Soyka
Re: 4:2:2 chroma subsampling, PCM audio, and 24-bit audio sample size - can I output these from After Effects?
on Apr 27, 2011 at 8:29:39 pm

[Mike Imam] "I failed to mention that this is an animated music video, so it wasn't using shot footage at all (did 100% of the animation in AE itself using Illustrator graphics). In this case, I assume the 4:2:2 chroma subsampling is done by default once I export?"

Yes, rendering to ProRes 422 will handle the subsampling for you.


[Mike Imam] "I use my Canon T2i as a primary camera, so should I not be converting these to ProRes for RTE in Final Cut (bit off topic) as I'll lose this information?"

No. Dave was referring to the fact that the H.264 DSLRs only record 4:2:0, and converting to ProRes (while it doesn't hurt), cannot re-create the missing chroma information. It's the camera itself that may not be suitable for 4:2:2 delivery requirements.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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Mike Imam
Re: 4:2:2 chroma subsampling, PCM audio, and 24-bit audio sample size - can I output these from After Effects?
on Apr 28, 2011 at 8:31:23 pm

Awesome - thanks for all the help!


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