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Joe Procopio
compression bitrate question...
on Sep 18, 2009 at 5:38:10 pm

i want to use compressor to compress an mpeg2 file for DVD...it's going to be about 150 minutes...i'm using the default setting in compressor...but that is for a DVD-5...i would like to modify it so the same mount of footage can go on a DVD-9 so I can bump up the data rate...is it as simple as just doubling the data rate setting for the DVD-5. or is it more complicated than that?


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Daniel Low
Re: compression bitrate question...
on Sep 18, 2009 at 6:42:23 pm

You shouldn't need to double it and you should never need to go over 8Mb/s + AC3 audio. Use 2-pass CBR for the video.

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."

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Joe Procopio
Re: compression bitrate question...
on Sep 18, 2009 at 10:28:41 pm

cool, thanks...but constant not variable? i'm testing variable 2 pass, with 7.7mbps to see how that works...

Broadway Video, NYC
AVID/FCP editor/engineer


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Daniel Low
Re: compression bitrate question...
on Sep 18, 2009 at 10:53:25 pm

VBR is for when you have to squeeze the maximum into the minimum. CBR is more of a guarantee of quality when you have the space available. It's obviously much more complicated than that but that's a very basic explanation

With VBR, it's essential that you use 2-pass. With CBR it's not.

Oddly enough both rate control methods do vary quite widely.

You say you are experimenting with 7.7Mbs 2 pass VBR, is 7.7 the peak or the average datarate?

__________________________________________________________________
"There's no chance that the iPhone is going to get any significant market share. No chance."

Steve Ballmer To USA Today


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Joe Procopio
Re: compression bitrate question...
on Sep 21, 2009 at 2:27:29 pm

7.7 is average...9 was peak...too much? it looked great...i only did a 15 min test chunk, so i can only hope the full 80 minutes won't be too big to fit everything.

Broadway Video, NYC
AVID/FCP editor/engineer


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Craig Seeman
Re: compression bitrate question...
on Sep 21, 2009 at 2:46:46 pm

Although the DVD spec says a max of 9.9, generally players won't handle that or 9 of that matter. Some older players may choke over 7. I'd keep the peak between 7.5 and 7.2 otherwise you're going to get lots of complaints. On the other hand if you've done an encode and it works on the specific player . . . but as soon as one moves to another player you'll likely have problems. In short, your numbers are way too high IMHO.



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