ADOBE AFTER EFFECTS: Forum Expressions Tutorials Creative Cloud

Transcoding footage for keying.

COW Forums : Adobe After Effects

<< PREVIOUS   •   FAQ   •   VIEW ALL   •   PRINT   •   NEXT >>
albert trevinoTranscoding footage for keying.
by on Dec 3, 2012 at 10:42:31 pm

Hi everyone.

Ok... here's the situation.

We have footage from 4-6 different cameras from 4 different locations that were shot a while back. It was all shot with subjects in front of a green screen and we need to key everyone before we do the actual editing. So from what I have seen from some research is that transcoding the footage may actually help with some of this.

1. It helps with ease of After Effects and Premiere with decoding the footage for editing easier.

2. It may help with some of the chroma subsampling from the original footage that is in AVC codecs.


Here is the workflow as of now that we are considering.

Transcode the footage from AVC/H.264 to ProRes 422(HQ).

Key in After Effects each shot in a separate comp.

Import through dynamic linking each keyed comp into Premiere and then proceed to editing.

----

ok.. so here are some questions.

1) Will it matter if I use 5DtoRGB to convert AVC/H.264 footage to ProRes or would other applications be suitable? I have used XMedia Recode to transcode files before and it does batch where as the PC version of 5DtoRGB doesn't do batch. (I am on a PC but a Mac is available if needed.)

2) ProRes 422(HQ) or ProRes 422? Is it overkill to take footage with the following attributes and use the 422(HQ) version rather than the regular 422 of ProRes?

Format : AVC
Format/Info : Advanced Video Codec
Format profile : Baseline@L5.0
Format settings, CABAC : No
Format settings, ReFrames : 1 frame
Format settings, GOP : M=1, N=12
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 7mn 29s
Bit rate : 44.7 Mbps
Width : 1 920 pixels
Height : 1 080 pixels
Original height : 1 088 pixels
Display aspect ratio : 16:9
Original display aspect ratio : 16:9
Frame rate mode : Constant
Frame rate : 23.976 fps
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.900
Stream size : 2.34 GiB (97%)
Language : English
Encoded date : UTC 2010-12-08 19:55:49
Tagged date : UTC 2010-12-08 19:55:49
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.601


3) If using 5DtoRGB to transcode, the Decoding Matrix should be based off of what exactly? From the attributes listed above it has:

Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.601


4) Would it better for ease of editing to just export out of After Effects the footage rather than dynamic link to Premiere? Decent PC with a G-Raid drive. Space could be an issue but can possibly be resolved.


Any insight before tackling full on into this major project would be greatly appreciated!


Return to posts index

Tudor "Ted" JelescuRe: Transcoding footage for keying.
by on Dec 4, 2012 at 7:30:59 am

You have 4:2:0 in the original- not great for chroma, so you do not want to loose any more color info. You will not get anything more from transcoding as far as the color info goes, but it will be faster to key in AE if you use an uncompressed format. In your situation I would convert to an uncompressed format, key, composite and render to ProRes and then import for edit.

Tudor "Ted" Jelescu
Senior VFX Artist


Return to posts index

albert trevinoRe: Transcoding footage for keying.
by on Dec 4, 2012 at 9:31:54 am

That's what I was thinking too. Converting to uncompressed would make the files almost too big for our current storage. We have about 1.3TB of footage in AVC/H.264 format. We would run out of space so quick.

Is there a reason to not use ProRes as a codec for keying footage? It would help with file size if I did in this process. Also being on a PC for the main editing wouldn't allow us to render out as ProRes to send to Premiere.


Return to posts index


Tudor "Ted" JelescuRe: Transcoding footage for keying.
by on Dec 4, 2012 at 11:50:40 am

I would do the clips one at the time- transcode- key- comp - render, then delete the large transcoded file, but that's my preference. The final format does not have to be ProRes, but whatever works with your PC Premiere workflow. I use a lot of MPEG2 for example.

Tudor "Ted" Jelescu
Senior VFX Artist


Return to posts index

Dave LaRondeRe: Transcoding footage for keying.
by on Dec 4, 2012 at 3:31:21 pm

ProRes is a really good codec. It's one of the few things Apple has actually gotten right lately for people who use professionally-oriented applications. I for one would indeed transcode to ProRes when ingesting the footage for edit.

You can save yourself a good deal of storage space by NOT using HQ: normal ProRes 422 will work just fine. The codec can withstand 6 generations of re-encoding before any visible image degradation occurs... and no sane person does that.

And if you can transcode to ProRes, it's a cinch you also have Final Cut Pro. Any reason you're not using it for cutting? FCP can export an OMF (or is it an XML? I forget) for Premiere Pro, and the latest version of AE also incorporates Automatic Duck, which lets you import FCP edit timelines as AE comps.

I'd also recommend cutting the project with NO keying, then doing the keying in AE if that's your chosen route. You'll save yourself both rendering time and storage.

Speaking of storage, you need more of it!

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


Return to posts index

albert trevinoRe: Transcoding footage for keying.
by on Dec 4, 2012 at 6:56:20 pm

Thanks for your replies.

Main editing is on PC, so FCP isn't an option nor do I have it.
The footage was taken by several different cameras and different locations, it wouldn't be easy to set up one key setting and have it work with all the footage after cutting it up. Therefore, it would be easier to key it in advance then do the compositing/editing in premiere. So the workflow has to be AE first for keying, then Premiere Pro for editing/compositing.

Most likely going ProRes into AE then export with alpha channel for editing in Premiere.

My main questions now are now:

1) Using 5DtoRGB, does it matter on the Decoding Matrix setting? ITU-R BT.601 or ITU-R BT.709?

2) What about converting the AVC/H.264 original to AVI (Lagarith Codec)[RGB] instead of ProRes for keying?

3) What about not converting the footage and using the original AVC/H.264 footage in AE for keying?

4) What would be the best option (keeping HD space in mind) when exporting out of AE for a file with Alpha channel? I was thinking AVI Lagarith [RGBA]


Return to posts index


Dave LaRondeRe: Transcoding footage for keying.
by on Dec 4, 2012 at 8:18:46 pm

If you don't have FCP, forget ProRes, then. You can't encode to it.

If you're really resolved to key first and cut later, run a test on your various shots in Premiere. It has a pretty darn good keyer, and it might just do the job for you, no AE necessary.

If the key's okay, you can key each camera's shots once, then copy & paste for subsequent shots from that camera. Thus you can indeed cut and key rather than key and cut.

You can also keep the footage in H.264. I presume you'll make backup copies of everything you shot.

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


Return to posts index

albert trevinoRe: Transcoding footage for keying.
by on Dec 4, 2012 at 8:59:49 pm

I figured I couldn't encode to ProRes out of AE without being on a MAC.

We actually went through all the footage in Premiere and using the ultra key plugin. It turned out ok, but some of the shots of people who have blonde hair and other odd aspects of each shot caused us to question our method. So maybe just using something more powerful with tweaks like AE for keying would work better overall.

I have read in several places that converting the footage from 8 bit 4:2:0 to 4:2:2 (or higher) using 5DtoRGB actually helps with color correction and keying in regards to color depth, etc. So this is why I am thinking of NOT using the original footage but instead converted footage.

Now coming out of AE into Premiere I could just use dynamic linking instead of exporting all the keyed footage. Just not sure about stressing out the computer to do basic editing with all that going on.


Return to posts index

Dave LaRondeRe: Transcoding footage for keying.
by on Dec 4, 2012 at 9:22:04 pm

[albert trevino] "I have read in several places that converting the footage from 8 bit 4:2:0 to 4:2:2 (or higher) using 5DtoRGB actually helps with color correction and keying in regards to color depth, etc. So this is why I am thinking of NOT using the original footage but instead converted footage."

Well, consider this: you will NOT be able to improve the color resolution by converting from 4:2:0 to 4:2:2. It just won't help on that score. Perhaps there's color grading software that requires the use of 4:2:2, which would be a good reason.

The reason to transcode is to prevent image degradation if you need to render or re-render to the same codec.

If you have concerns about taxing your computer, you're the only one who could know that: at the moment, only you know your machine's specs.

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


Return to posts index


albert trevinoRe: Transcoding footage for keying.
by on Dec 4, 2012 at 11:11:53 pm

Hmmm...

Actually through further inspection. We only had one shoot that has 4:2:0 footage. One was shot on a RED and others on XDCAM EX 35 with all being 4:2:2.

So I am thinking revisiting all the already keyed attempts in Premiere we did and the one's that look questionable, take those to After Effects for keying.

What a pain... but... with little budget we couldn't get a consistent camera the whole time. We had to hire locally while the shots where at different places in different states.

Gotta work with what you got!

I am trying to keep the workflow simple and less taxing on computers and HD space.


Return to posts index

<< PREVIOUS   •   VIEW ALL   •   PRINT   •   NEXT >>
© 2017 CreativeCOW.net All Rights Reserved
[TOP]