work out file size from bit rate and time

Discussion in 'Other video questions' started by p4000, Jan 31, 2006.

  1. p4000

    p4000 Member

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    Hi, i feel very silly havign to ask this but,

    does anyone know the formula to use to calculate file size when you know the bit rate and time.

    eg

    1 hr of video encoded @ 10Mbits / sec

    what would the file size be in Giga "bytes"?

    i have tried to work it out but i keep comming up with the wrong figure and this is really anoying me now!!

    thanks
    p4000
     
  2. celtic_d

    celtic_d Regular member

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    1Byte = 8bits. 1024 bytes per kiloByte, 1024 kB per megaByte.
    For video 1,000 is used instead of 1024.

    With video, when it is in a container (esp with audio) there is overhead, so the size isn't simply a matter of bitrate*time.
     
  3. p4000

    p4000 Member

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    Yep, thanks - i've actually found the formuala now so i'll print it here in case anyone else needs to know / wants to know.

    [bold]bit rate (kbps) x file length (seconds) / 8 = file size (KB)[/bold]

    obviously you'll have to convert Kilobytes into Mb's or Gb's or you can use this very handy calculatorhttp://www.clipstream.com/help/filesize.shtml

     
  4. Minion

    Minion Senior member

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    What I use is a "Bitrate Calculator" called "PowerBit" which will tell you what Bitrate to use Based on the Length of the Video File and the audio Bitrate you are going to use so the Video fits on a DVD-R.....

    I have been useing it for a Couple Years now and it has allways worked Prefectly for me.....Do a Google search and you will find it easilly enough....

    Cheers
     
  5. p4000

    p4000 Member

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    thanks minion but it was trying to acheive the oposite.

    i neeeded the work out [bold]file size[/bold] of a [bold]elementary[/bold] video file based on the bit rate that would be used to encode and the length of the video.

    example; i use a 25Mpbs encoder, i know that i will need to encode 5500 hours of video @ this rate, how much storage do i need?

    your method requires the work to have been done first.

    good try though, but if you see a few post up i have already found a solution.

    thanks anyway
    p4000
     

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