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CBR vs. VBR encoding?

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VideoFlyer
CBR vs. VBR encoding?
on Oct 7, 2005 at 5:01:23 pm

I'm working on a skydiving video project which naturally has a lot of fast movement. It will be about 1 hour long, I've read somewhere but can't seem to find it now that you should always use CBR(constant bit rate) for anything less than say 60 min. but use VBR(variable bit rate) for anything longer than that expecially if there is a lot of movement or a lot of transitions due to the space on DVD's. Am I remembering this correct? Or should I still use VBR since there is a lot of movement and there will be many transitions too?
I'm usisng DVDit! 5, any suguestions for doing this project would be greatly appreciated.


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John Q
Re: CBR vs. VBR encoding?
on Oct 7, 2005 at 9:55:51 pm

I own a Matrox RT.X100 system, and Matrox recommends a maximum bitrate of 7.0 Mb/sec CBR for the video. That's because the DVD spec is a maximum total bitrate of 9.8 for video and audio combined. At 7 CBR, you'll still see some spikes that exceed 7. If your audio is encoded as PCM, then you'll safely be under the maximum limit.

For longer projects, Matrox recommends using VBR with a lower bitrate, although I've seen some DVD players that will be jerky with VBR encoded DVD-R discs that will play CBR encoded discs perfectly.


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VideoFlyer
Re: CBR vs. VBR encoding?
on Oct 9, 2005 at 1:46:11 pm

Thanks John for the reply. With DVDit! 5 I sometimes get this error message, 'Decoding of audio failed, DVDErr, -47007'. Sometimes I get it and sometimes I don't, any idea whats causing this error message? I don't get this error message if I go through Sorenson Squeeze to encode the sequence, but it seems as though DVDit! wants to re-encode the compliant mpeg 2 file again. Was wondering if DVDit! 6 Pro handles this better?


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John Q
Re: CBR vs. VBR encoding?
on Oct 9, 2005 at 11:43:40 pm

I learned a long time ago with DVDit 2.5.4 that the most efficient import method is primary streams, i.e. separate video and audio files. If you import a multiplexed stream, then the first task DVDit will perform is to demultiplex your input into separate video and audio files, which takes up more time and drive space. Since my RT.X100 allows me to choose how to export, I always create separate video and audio files, using its realtime transcoding capability to create m2v and wav files. Although I now use Encore, it still saves time.

I've read about problems with DVDit 5 that seem to have been cured in version 6, although I don't have any personal experience with this, since I upgraded to Encore and the Adobe Video Collection.


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