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How to render a Video without the background

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Anil Simsik
How to render a Video without the background
on Feb 14, 2011 at 3:20:24 pm

I want to make a After Effects template, but the I used trapcode particular and not all have particular. So I want to prerender the particular. I tried it with bg+alpha, but the quality was to bad and the file was to big (800mb). Can someone help me to create a not so big file, without a background and a good quality?

Thank you.


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Jason Mettler
Re: How to render a Video without the background
on Feb 14, 2011 at 3:32:36 pm

Sorry if this posts twice. Try making any layer you don't want to include in the render a 'guide layer'. Right-click on the layer and select 'Guide Layer'. A small blue number sign will appear by the layer name. This will leave the layer in comp view but will hide it during renders and in any comps the layer is nested in.


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Anil Simsik
Re: How to render a Video without the background
on Feb 14, 2011 at 6:17:56 pm

I dont want to hide something. I want to prerender my particles, but without a background, no black background, just transparent.


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Dave LaRonde
Re: How to render a Video without the background
on Feb 14, 2011 at 6:33:25 pm

[Anil Simsik] "I want to prerender my particles, but without a background, no black background, just transparent."

Then you make sure you have any field order rendering issues settled, you make sure you actually HAVE transparency by toggling the alpha channel switch, you prerender in a lossless codec that supports alpha channels, you make sure you render rgb+alpha, millions (or trillions) of colors +, and you deal with the resulting file size.

If you can't do that, it's time for Plan B.

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


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Anil Simsik
Re: How to render a Video without the background
on Feb 14, 2011 at 7:24:15 pm

I did this, but the quality of the prerendered particles is very bad and the file is to big.


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Jason Mettler
Re: How to render a Video without the background
on Feb 14, 2011 at 8:36:03 pm

You can alter the codec of a quicktime compression to say mp4 instead of 'animation'. You will trade quality for size no matter what, but I do that occasionally to save size. You also have the option of using Premiere Pro or Final Cut to resample you movie file. I also do this on occasion. Render out of AE in QT and then export out of Premiere in FLV or MPG2.
Are you confident your particular settings are right?


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Dave LaRonde
Re: How to render a Video without the background
on Feb 14, 2011 at 8:52:50 pm

[Jason Mettler] "You can alter the codec of a quicktime compression to say mp4 instead of 'animation'. "

Unfortunately, mpeg 4 video doesn't support alpha channels. Quicktime's PNG codec (not the sequence) does in addition to Animation, and every current version of QT7 Pro on the planet can read and write to it.

I agree: there's something fishy about settings someplace, and "looks bad" doesn't give anybody a lot to go on from a diagnostic standpoint.

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


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Jason Mettler
Re: How to render a Video without the background
on Feb 14, 2011 at 10:17:31 pm

Thanks for the clarification Dave!


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Anil Simsik
Re: How to render a Video without the background
on Feb 15, 2011 at 4:26:42 pm

it works now fine, but the file size dont changed. Do you know how i can make the file about 30mb big?


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Dave LaRonde
Re: How to render a Video without the background
on Feb 15, 2011 at 4:39:48 pm

If you want this footage to have an alpha channel, you must keep the large file size. You have no choice.

In footage with NO alpha channel, you can make a tradeoff between large file size and image quality. You can't do that in footage with an alpha channel. So if the large file size is unacceptable, it really IS time for Plan B.

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


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Anil Simsik
Re: How to render a Video without the background
on Feb 15, 2011 at 9:02:44 pm

Two questions: what is plan b?
And how did Andrew Kramer created his footage, is a .mov file and not that big?


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Dave LaRonde
Here's Plan B
on Feb 15, 2011 at 9:11:53 pm

To reduce file size, you can do a number of things:
  • If it's practical, you can reduce the comps size by half. For example you can change the size from 1280x720 to 640x360.
  • Instead of creating an alpha channel, you can create a Matte that will do the same thing by rendering the alpha channel only. It will create a white- on black image, where 100% white is totally opaque, 100% black is totally transparent, and shades of gray are semi-transparent. These files can be compressed more.
  • Create a color image of the animation with no embedded alpha channel. This can also be compressed more, and you use it in conjunction with the matte footage created as described above. You use the B&W matte as a Luma Matte in AE.

Those few things will help to reduce file sizes a lot. You simply have to work in a different way than you wanted to work.

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


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Anil Simsik
Re: Here's Plan B
on Feb 15, 2011 at 9:24:08 pm

Thank you for your help! I will try Plan b and I think this should be working.


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Haris Berbić
Re: Here's Plan B
on Apr 29, 2015 at 9:43:21 am

Hello Dave!

Please can you clarify one thing here: in terms of transparency and file size, it is possible to create separate Alpha channel video in .mp4 and then another in RGB, but I found this not working when imported in Premiere Pro or After Effects and I am missing here something so I ask you what could that be.

Thanks!


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