Any info yet on video bitrates?

Discussion in 'General Discussions' started by JelleSE, Oct 22, 2016.

  1. JelleSE

    JelleSE New Member

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    I understand that the max bitrate in 4K is 60 Mbps, but how about 2.7k and 1080p? Still 60Mbps or is it lower?
     
  2. camfirstflyer

    camfirstflyer Active Member

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    I had a chat with DJI about this.. here's what I was able to get:

    • 60 mbps is a constant bit rate
    • it will record at 60 mbps at 4k on either PAL or NTSC
    • the bit rate will remain at 60 mbps at lower resolutions (I specifically asked about 2.7k)
    • compression (rate?) is not lower at resolutions lower than 4k (i.e., 2.7k)

    They couldn't give me an explanation of why for this last point, hehe ("too complicated")
     
  3. repentsinner

    repentsinner New Member

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    Looks to me like we don't get 60Mbps across the board :(

    I shot a test clip of 2.7K@30, and it's 44Mbps all the way through. My Mavic is at FW 01.03.0200.

    Do you see different results somehow?
     

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  4. camfirstflyer

    camfirstflyer Active Member

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    hmm.. I'm curious if it is technically possible to change the bitrate through a software update?

    If so, what are the drawbacks, besides file size and dependence on faster, more expensive micro SD cards?
     
  5. halley

    halley Well-Known Member

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    There is only so much computing power dedicated to image processing on the drone. Perhaps the existing chips have no higher modes. Perhaps the existing chips have higher modes, but they're unreliable with the bandwidth to the average microSD card, and DJI didn't want to suffer product returns and bad reviews due to slow microSD cards. Perhaps the existing chips have higher modes, but need a faster clock and more cooling to achieve it.
     
  6. kaitlyn

    kaitlyn Well-Known Member

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    Wouldn't doing 2.7k @ 60mbps being easier than 4k @ 60mbps? Seems weird the lower res ALSO gets a lower bitrate
     
  7. repentsinner

    repentsinner New Member

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    I'm not sure what your speculation is adding to the discussion, aside from being apologetic to DJI for some reason.

    If 4K mode is recorded at 60Mbps then 60Mbps is available to write to the SD card. It shouldn't matter what the input resolution is. We should be able to use 2.7K, 1080p or 720p at 60Mbps.

    In video compression, less compression (higher bitrate) is almost always easier from a computational perspective. DJI would have had to select a very sub-standard compression chip or system design for this not to be the case.

    The video recording capabilities/limitations of the Mavic 'Pro' are compression-bound rather than sensor-bound, resulting in sub-standard files which don't do the sensor justice.
     
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