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Why does PCM audio setting bloat my project from 12 gigs to 28 gigs?

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Stuart Baker
Why does PCM audio setting bloat my project from 12 gigs to 28 gigs?
on Mar 11, 2009 at 3:17:59 am

Hello,

I have a Blu-ray DVD project with roughly 10 gigs of assets imported into a single timeline:

MPEG-2 HD Video - 1920x1080, 25Kbps, 23.976

Uncompressed .WAV audio - 48 Khz, 16 bit

When I attempt to "build" the DVD with "PCM" as my audio preset, I am told that my project contains roughly 28 gigs of media, and can't be built with my single layer Blu-ray disc.

The same Blu-ray project, with the preset set to "Dolby Digital", instead of PCM, comes out to 12 gigs of media.

I prefer to go with PCM, so I don't have to retranscode my audio files. I do not understand how a 12 gig project (with only 10 gigs of media, mind you) becomes a 28 gig project because of a change in the audio compression setting. I understand that uncompressed .wav with PCI encoding are considerably bigger than Dolby Digitally compressed .wav files, but it's hard for me to believe that the difference for an hour of audio content is 16 gigs.

Is this possible? Or am I doing something incorrectly, or missing a setting, in Encore CS4?

Thanks,





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Andrew Ford
Re: Why does PCM audio setting bloat my project from 12 gigs to 28 gigs?
on Mar 24, 2009 at 7:08:42 pm

PCM audio is huge in size...can be 10 times the file size of AC3.
It's often referred to as uncompressed because most of the compression in PCM is done on the outer frequencies. There is a quality advantage to PCM compared to compressed .AC3, but .ac3 is usually recommended for DVDs because of the good quality in a smaller size. Try to use .ac3 when possible.


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