Understanding variable bit rates

Discussion in 'Computers' started by John_Berger, Jun 2, 2003.

  1. John_Berger

    John_Berger Cinematographer

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    This is more of a technical curiosity than anything else, but every web site that I visit gives me a definition for "variable bit rate". Well, DUH! Could it possibly mean that "variable" means "changing"? Imagine that. [​IMG]

    I'm starting to play with variable bit rates now that (from what I understand) DVDit PE has better chapter support for variable bit rate MPEG-2 files, so I'd like to take advantage of that. But I'm just curious about it because I still need to set a bit rate when creating the MPEG-2 file.

    What's the purpose of this setting? Maximum bit rate? Average? Optimal? How does the encoder determine the best per-frame bit rate based on this number?

    Again, just technical curiosity, but most web sites that I've seen give me the vanilla definition that I already know.
     
  2. John_Berger

    John_Berger Cinematographer

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    [​IMG] Thanks! I figured that it was more of an average than anything else, but I wasn't sure. Unfortunately, MSP 6.5 appears to be 1-pass VBR. Maybe that's different in v7.0.

    As to that last link ... you intentionally wanted to see if my brain would explode, didn't you? [​IMG]
     
  3. Ken Chan

    Ken Chan Producer

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    Didn't work, huh? [​IMG]

    If an encoder did two-pass VBR, it would probably mention it prominently, since it is a higher-end feature.

    //Ken
     
  4. John_Berger

    John_Berger Cinematographer

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  5. John_Berger

    John_Berger Cinematographer

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