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Alpha Banding

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Paul Rozon
Alpha Banding
on Dec 31, 2011 at 5:38:00 pm

I posted this on PP group without success. I am thinking maybe it is an AE problem. I have attached the Project file and a couple pics to demonstrate the banding. I have been going at this for a few days trying every variation that I can think of without success. Any input would be greatly appreciated.







3475_songwriterscomminoutlowerthird.aep.zip

System/Software
HP Z400 Workstation
Matrox MX02LE
Windows 7 Profesional - Service Pack 1
12Gb RAM
Adobe Production Bundle Suite 5.5
NVidia Quadro 4000

Sequence Preset
Matrox - HD 1080i @ 29.97

FX Media Vid Track 02
After Effects composition - 1080 x 1920 @ 29.97
lower third scrolling text
Rendered as - Matrox AVI uncompressed RGB + Alpha

Source Media Vid Track 01
Line Cut - Panasonic HS400 Switcher
Recorder - Panasonic P2 Recorder AJ-HPD2500P
AVC-I 100 @ 1080i 60

First problem I encounter is the export from AE. I select AVI - Matrox Uncompressed + Alpha but the Alpha option is greyed out (jpg attached). Anyone else experiencing this?

Instead I export as Matrox Mpg-2 I-Frame + Alpha without problems.


In PP I have source media on track 1 and AE lower third scrolling text on Track 2 (above track 1). Everything looks prestine on PP program monitor and on external production monitor. Export timeline and severe banding occurs.

I have attempted exporting AE file in a number of different file types without any difference. I have also attempted exporting PP sequence in a number of different files types without success.




--
Paul Rozon


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Dave LaRonde
Re: Alpha Banding
on Dec 31, 2011 at 5:50:35 pm

I'm an FCP guy, so I don't know this for sure. Can you change the bit depth of Premiere projects, say from 8 bits to 16 bits or more?

It also may halp to work in 16 bits or even 32 in AE for the Alpha-
channeled animated lower-thirds.

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


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Paul Rozon
Re: Alpha Banding
on Dec 31, 2011 at 6:11:45 pm

PP allows you to go from 8 bit to 11 bit in the Matrox sequence settings. Does not make a difference.

I also experimented with 8, 16 and 32 bit in AE and no difference.

I appreciate the suggestions.


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Erik Waluska
Re: Alpha Banding
on Dec 31, 2011 at 6:40:46 pm

Could you post a CS5 version of your project file?


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Paul Rozon
Re: Alpha Banding
on Dec 31, 2011 at 7:37:08 pm

Not at my workstation right now but I will upload a cs5 version as soon as I can. Thanks for your interest.


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John Cuevas
Re: Alpha Banding
on Dec 31, 2011 at 8:16:37 pm

Couple of things. First when I tried to render out an HD file to a AVI with RGB + Alpha, it was unavailable in both HD or SD sizes. If I chose avi with the codec set to none, I was able to render to a RGB+Alpha. Of course umcompressed AVI's are very very large files, but you can always take that file into Media Encoder.

I posted last week on video banding:

Bit depth can a difference on banding


If the video is for HD delivery, Kevin Camp's offered a recipe that has worked well for me in the past.

as for banding, you can usually add an adjustment layer with the noise effect on it. it shouldn't take much noise (less that 5%) to hide the banding.

Roland Kahlenberg offers some notes if for web delivery.

Blurring one or more of the color channels does a better job for reducing or eliminating banding problems. Adding noise more to a comp which may be destined for Web delivery will only result in a poorer quality web version as compressors usually have a harder time compressing noise.

Use Effect>Channel Blur and increase one of the values to solve your problem. You can tell which channel needs more attention by looking at the individual color channels in the Comp Panel prior to applying Channel Blur.


Johnny Cuevas, Editor
Thinkck.com

"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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Paul Rozon
Re: Alpha Banding
on Jan 1, 2012 at 3:31:59 pm

I have experimented with everything at its highest bit rate without success.

What I find confusing is why the alpha keys perfectly on my PP timeline in realtime. That would suggest to me that the alpha is good and that something is going wrong in the render. Is this logic flawed?


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Tudor "Ted" Jelescu
Re: Alpha Banding
on Jan 1, 2012 at 11:40:31 am

I would do the compositing all in AE @ 32bit and render uncompressed. I would then use Encoder to compress the final. This usually eliminates any banding issues.

Tudor "Ted" Jelescu
Senior VFX Artist


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Paul Rozon
Re: Alpha Banding
on Jan 1, 2012 at 3:34:41 pm

The same suggestion was made in PP forum.

Certainly an option that I will explore but I am confused as to why the alpha looks perfect on PP timeline in realtime and it only craps out on the render?


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Tudor "Ted" Jelescu
Re: Alpha Banding
on Jan 1, 2012 at 6:13:04 pm

Most likely you loose info in compression. Try to render an uncompressed format from PPro and see if you have the same results.

Tudor "Ted" Jelescu
Senior VFX Artist


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Paul Rozon
Re: Alpha Banding
on Jan 1, 2012 at 7:47:54 pm

Just rendered it out as Microsoft AVI, codec set to NONE. Banding still there.

I can see where the render might add some subtle compression banding but what I am experiencing is well beyond that as you can see from the JPG's that I have attached.

It is a 90min program with many instances of this effect. Bringing everything into AE just to get a clean render and then back into PP is going to kill me for time. Then once the alterations come in it is going to get rediculous.

Is this what the norm is for AE alpha? Or am I dealing with a unique problem?


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Tudor "Ted" Jelescu
Re: Alpha Banding
on Jan 2, 2012 at 10:56:29 am

I have never encountered this issue with alpha from AE in PPro, but then I do all the complex compositing in AE and use only simple gfx with alpha in PPro.

Tudor "Ted" Jelescu
Senior VFX Artist


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Paul Rozon
Re: Alpha Banding
on Jan 2, 2012 at 8:14:52 pm

Turned off the mercury hardware accelerator in PP and went to software render and everything looks fine now. Not sure what this means but I got my show out for now


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Tudor "Ted" Jelescu
Re: Alpha Banding
on Jan 2, 2012 at 8:55:04 pm

That makes sense- make sure to mention that you render using hardware acceleration. Usually you get best results when rendering using the CPU and not hardware acceleration.

Tudor "Ted" Jelescu
Senior VFX Artist


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