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optimizing an MPEG-2 dompression.

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thewanggao
optimizing an MPEG-2 dompression.
on Dec 31, 2005 at 5:59:25 am

Hi,
I've shot and edited a project in fcp that runs about 15 minutes long. I have encoded a DVD test so far using Compressor 2, with mediocre results, using a 2-pass VBR at 7.9 avg. data rate and max of 9 MBPS data rate. My frames are 720 x 480 anamorphic.

I've heard somewhere that the data rate shouldn't be so high. Why is this the case? What is a better data rate? Also, some of my transitions were choppy. Does this have anything to do with the 2 pass that i have set?

MUCH THANKS

Alexander Gao

"When the revolution happens, I'll be leading it."


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Charles Simonson
Re: optimizing an MPEG-2 dompression.
on Dec 31, 2005 at 6:44:53 am

Apple has a pretty good MPEG-2 encoder in Compressor 2, and at that data rate, it should be able to produce nice results. One of the reasons why you may not want to use that high of a data rate though, is because some DVD players can not handle the rate on recorded DVD-Rs. So, if you are seeing lots of artifacts, especially at transition scenes, where the bit rate can spike, then it could be the DVD player and not the actual encode. Typically, very high-quality SD MPEG-2 encoding can be achieved at rates around 6.5mbps with most decent software encoders these days. And it is very doubtful that 2 pass encoding "introduced" the choppiness.

Another issue may be if your source is interlaced. If you are planning the disc for playback with a television, it is best to leave the encode interlaced. If you are only going to watch the disc on a computer though, then deinterlacing may help in improving quality (not always though).


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thewanggao
Re: optimizing an MPEG-2 dompression.
on Dec 31, 2005 at 7:13:25 am

THANKS SO MUCH Charles.
I have one more question for you or anybody else. Should I leave the DVD footage interlaced if it will be played on a DVD player that is hooked up to a projector rather than a television?

thanks for the help.

Alexander Gao

"When the revolution happens, I'll be leading it."


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Ben Waggoner
Re: optimizing an MPEG-2 dompression.
on Dec 31, 2005 at 9:31:09 pm

Any modern software DVD player should interlace the video before it goes out to the projector. A good DVD player with interlaced source will upconvert with adaptive deinterlacing to 480p60. If you deinterlace before encode, the best you can get out is 480p30, so I'd keep the interlacing assuming you're using a good player.

My Book: http://www.benwaggoner.com/books.htm
Squeeze and ProCoder tutorials: http://www.classondemand.net/benwaggoner/
Compression Class at Stanford: http://www.digitalmediaacademy.org/compression.html


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RoRK
Re: optimizing an MPEG-2 dompression.
by
on Jan 18, 2006 at 3:09:11 pm

[Ben Waggoner] "Any modern software DVD player should interlace the video before it goes out to the projector."

I believe Ben meant deinterlace here.

Cheers
RoRK
broadcastGEMs
customizable animated backdrops with Adobe After Effects project files


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