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render using PNG question

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Anhtu Vu
render using PNG question
on Mar 23, 2011 at 6:11:37 pm

after testing several different CODECS for my render output, i chose PNG as it was giving me the best result once the file is further processed to H.264 via compressor. The other Codecs i tried looked great but i noticed some artifacts once it has been compressed to H.264.

When playing back the PNG file ( 1920x1080 @ 29.97 ), the image is stuttering, is this normal ??? ( the same PNG file compressed to H.264 plays fine )



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Dave LaRonde
Re: render using PNG question
on Mar 23, 2011 at 6:13:43 pm

[Anhtu Vu] "When playing back the PNG file ( 1920x1080 @ 29.97 ), the image is stuttering, is this normal ?"

Yes -- your computer's hard drive can't keep up with the high bit rate of the file. It happens a lot with uncompressed or lossless video.

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


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Anhtu Vu
Re: render using PNG question
on Mar 23, 2011 at 6:23:11 pm

Are you sure ??? My project is on my external Raid ( 600 Mb/s ). It breezes through uncompressed 10 bits so i don't think it's a hard disk is the issue. Anyone knows of the PNG hard disk requirements ???



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Walter Soyka
Re: render using PNG question
on Mar 23, 2011 at 6:47:27 pm

[Anhtu Vu] "When playing back the PNG file ( 1920x1080 @ 29.97 ), the image is stuttering, is this normal ??? ( the same PNG file compressed to H.264 plays fine )"

I recognize your name from the Smoke forum, so I'll assume that your storage is not the problem (although it is for most folks). PNG is highly compressed (but losslessly), so it's got some pretty high CPU requirements.

In general, PNG-compressed movies aren't meant for realtime playback. This is an intermediate format (for exactly the purpose you're using it), not a playback or delivery format.

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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Anhtu Vu
Re: render using PNG question
on Mar 23, 2011 at 7:01:44 pm

I do all my work off the same Raid that i use for Smoke so i don't think hard disk is the issue. I'm using a dual 2.8 mac pro so maybe my CPU is not up to par, again, most unlikely.
From what i understand, PNG is a graphic and not a video Codec, therefore realtime playback is not possible.



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Dave LaRonde
Re: render using PNG question
on Mar 23, 2011 at 7:14:11 pm

PNG is both a video codec and a still image file type. It's a bit confusing.

And just for the heck of it, I converted a 30-second, 320x240, 29.97 mp4 file in H.264 compression into an alpha-channeled PNG-codec quicktime at the same resolution but at 59.94. I don't recommend doing it; it took forever and a day.

The H.264 file: 3.25 MB
The PNG-codec file: 620.05 MB! Yipes!

And for all the reasons discussed, PNG isn't the best thing to play. It's a great intermediate codec, it's just not intended for realtime playback.

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


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