Dashcams' write speed

Discussion in 'General Dash Cam Discussion' started by Module 79L, Sep 28, 2017.

  1. Module 79L

    Module 79L Well-Known Member

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    How do you calculate it? Is it fixed or depends on things like the bitrate, the resolution, the type of chipset, the firmware, etc?
     
  2. kamkar1

    kamkar1 Well-Known Member

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    Take a 3 minute file, let say it is 340 MB in size, divide that with the 180 seconds that make up 3 minutes, and you have the amount of Megabytes / second the camera have been writing at.
    Memory cards as you know list their speeds in Megabytes/ second.

    In this example that would be a write speed of 1.88 MB/ second the camera have been writing.

    Off course if the camera use variable bitrate you will see different file sizes, but daytime driving should provide the worst case scenario, night time recordings file size can be significant smaller with a VBR camera.

    If it is a VBR camera then in parts of that 3 minute recording the camera might have been writing at 3 MB/s and then other parts it might only have been writing at 0.8 MB/s

    The above are the average write speed you are getting, but if your action in the footage have been the same thruout the 3 minute recording you can also be sure the bitrate the camera have chosen to use have been pretty much the same.
     
    Last edited: Sep 28, 2017
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  3. Module 79L

    Module 79L Well-Known Member

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    So, are these calculations right or wrong:
     
  4. Nigel

    Nigel Well-Known Member

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    Looks OK, however the mbps are given in the file properties, sometimes given in kbps so you need to divide by 1000.

    If it is a variable bitrate file then you really want the maximum bitrate, there is a application called "Bitrate Viewer" which will show you more detail of what is in the files.
     
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  5. jokiin

    jokiin Well-Known Member Manufacturer

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    correct but confusing due to Mb or MB, 16Mb/Sec is only 2MB/Sec, similar numbers to the example @kamkar1 provided although he explained it clearer
     
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  6. Module 79L

    Module 79L Well-Known Member

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    So, in which value is the microSD cards' write speed expressed in? MB/s or Mb/s?
     
    Last edited: Sep 29, 2017
  7. jokiin

    jokiin Well-Known Member Manufacturer

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  8. Module 79L

    Module 79L Well-Known Member

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  9. Hombré

    Hombré Active Member

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  10. jokiin

    jokiin Well-Known Member Manufacturer

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    we like to include cards is to make sure people have the right type of card, but mainly to make sure they get a genuine card, so many fakes out there
     
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  11. estore009

    estore009 Active Member Retailer

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  12. jokiin

    jokiin Well-Known Member Manufacturer

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  13. Hombré

    Hombré Active Member

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    Unfortunately most camera failures that I see on this forum seem to relate seem to the card
    Once again..... Fakes will be eliminated with a supplied card by the manufacturer
     
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