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Thread: Calculate Bitrate

  1. #1
    Join Date
    Oct 2011

    Default Calculate Bitrate

    Everytime I create a movie in Premiere Pro and export it to .flv I need to insert a Bitrate which is logical.
    So I use an online calculator that works just fine (Flash Video (FLV) Bitrate Calculator)

    But to get a little more advanced I want to know how the bitrate is calculated.
    I've Googled for a couple of minutes to be honest, but maybe someone has the answer for me and saves me some time.


  2. #2


    I found this if it helps.

    Manually calculate the bitrate
    The basic bitrate formula is

    (Size - (Audio x Length )) / Length = Video bitrate L = Lenght of the whole movie in seconds
    S = Size you like to use in KB (note 700 MB x 1024 = 716 800 KB)
    A = Audio bitrate in KB/s (note 224 kbit/s = 224 / 8 = 28 KB/s)
    V = Video bitrate in KB/s, to get kbit/s multiply with 8.

    8 bit = 1 byte.
    1024 = 1 kilo in the computer world.

    90 minutes video, L = 90 x 60 = 5 400 seconds
    700 MB CD but be sure that if fits use a bit lower like 695 MB, S = 695 x 1024 = 711 680 KB
    Audio bitrate, A = 224 kbit/s / 8 = 28 KB/s

    (711 680 - (5400 x 2 ) / 5400 = 104 KB/s x 8 = 830 kbit/s.

  3. #3
    Join Date
    Oct 2011


    Ah great. I'll check it out in a bit!

  4. #4
    Join Date
    Oct 2011



    I've tried this, but this calculates for the export on a 700 MB CD. I need to calculate the Bitrate for a .fv file based on the aspect ratio. So I don't know the filesize maximum.
    I am going to Google my ass of to find it. If there is someone who knows... Please!

    Thnx Midnight Blue

  5. #5


    I recommend contacting the site's owner to find the maths they have used in the online calculator.
    Even so, that calculator is only a rough guide - and I am not at all sure how accurate it can be. The User must select the appropriate 'motion' dropdown from "slow/Medium/fast'. It makes a huge difference in the results; as does the choice of codec (e.g. Sorenson). I don't know the algoritham used in FLV files, but I can accept that, bit for bit, wider aspect ratios may be easier for codecs to compress (and therefore use lower bitrates).

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