How does bitrate work?

Discussion in 'DVD' started by Allan^L, Jun 18, 2004.

  1. Allan^L

    Allan^L Stunt Coordinator

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    On my JVC DVD player, there's a button that lets me see the bitrate of the DVD currently playing. When I read reviews, the bitrate is mentioned as being 6.5 or 8.0 or whatever. When I press this button though, the bitrate fluctuates wildly, changing every second. How do you know the bitrate is 6.5 (for example) when the number keeps changing?
     
  2. Allan^L

    Allan^L Stunt Coordinator

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    On my JVC DVD player, there's a button that lets me see the bitrate of the DVD currently playing. When I read reviews, the bitrate is mentioned as being 6.5 or 8.0 or whatever. When I press this button though, the bitrate fluctuates wildly, changing every second. How do you know the bitrate is 6.5 (for example) when the number keeps changing?
     
  3. Lev-S

    Lev-S Second Unit

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    What you are seeing is VBR (Variable Bit Rate). Basically, certain colors and patterns in video information contain more or less information than others and require more or less size (bits) to store it in. Just like MP3s, a higher bit rate usually means a better picture, which is co-dependant on the source material. Hope that was somewhat clear! [​IMG]
     
  4. Lev-S

    Lev-S Second Unit

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    What you are seeing is VBR (Variable Bit Rate). Basically, certain colors and patterns in video information contain more or less information than others and require more or less size (bits) to store it in. Just like MP3s, a higher bit rate usually means a better picture, which is co-dependant on the source material. Hope that was somewhat clear! [​IMG]
     
  5. Michael Reuben

    Michael Reuben Studio Mogul

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    That's the average bitrate. I've often wondered, though, how reviewers go about determining the average.

    M.
     
  6. Michael Reuben

    Michael Reuben Studio Mogul

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    That's the average bitrate. I've often wondered, though, how reviewers go about determining the average.

    M.
     
  7. Ryan FB

    Ryan FB Second Unit

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    The probably use a tool like Bitrate Viewer. Certainly beats doing the calculations on pen and paper. [​IMG]
     
  8. Ryan FB

    Ryan FB Second Unit

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    The probably use a tool like Bitrate Viewer. Certainly beats doing the calculations on pen and paper. [​IMG]
     
  9. Jeff Jacobson

    Jeff Jacobson Cinematographer

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  10. Jeff Jacobson

    Jeff Jacobson Cinematographer

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  11. Roger_R

    Roger_R Second Unit

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    The big question is, how come they didn't make AC3 VBR-capable? [​IMG]
     
  12. Roger_R

    Roger_R Second Unit

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    The big question is, how come they didn't make AC3 VBR-capable? [​IMG]
     
  13. Mark_vdH

    Mark_vdH Screenwriter

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    Isn't the average bitrate also easily calculated by dividing the amount space the movie takes (in Mbits) with the total length (in seconds) of the movie?
     
  14. Mark_vdH

    Mark_vdH Screenwriter

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    Isn't the average bitrate also easily calculated by dividing the amount space the movie takes (in Mbits) with the total length (in seconds) of the movie?
     
  15. Christ Reynolds

    Christ Reynolds Producer

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    if you can determine the amount of space the video material takes up, yes. since the audio is at a fixed bitrate, this shouldnt be too hard of a task.

    CJ
     
  16. Christ Reynolds

    Christ Reynolds Producer

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    if you can determine the amount of space the video material takes up, yes. since the audio is at a fixed bitrate, this shouldnt be too hard of a task.

    CJ
     

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