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Video Mbps and Size

Discussion in 'Pro/Adv Discussion' started by GaryDZ, Aug 4, 2016.

  1. GaryDZ

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    I have a P3A. I record video at NTSC 1080 30fps. A few month ago I looked at the specs of my video file with Media Info. It was recorded at 11.0 Mbps. Today's file was recorded at 40.0 mbps. What brought this to my attention was the fact that the 11 Mbps video could not exceed the 4GB file size limit of the exFAT SD card, but the 40 Mbps video does. The only differences between now and then are firmware updates and the use of a ND filter with manual exposure settings. I was shooting ND16, ISO 100, 1/60 fps. Does anyone know what's going on?
     
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  2. GaryDZ

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    No one?
     
  3. Digdat0

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    My gut is that the 11mbps is 1080p, but the 40mbps is actually 2.7k. I'm interested I kmowing more .. Cause I hate the cut off on 4gb files cause it to remove a second of video time in there, and makes it hard to sync a screen recorder with it.

    What firmware version were you on, and what are you on now? I'll see if I can find anything.
     
  4. Digdat0

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    Dji's website shows the max Mbps for the 2.7k is 40mbps .. So that's maxed out, had to be 2.7k

    [​IMG]
     
  5. P3A_Demon

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    Well I don't have an answer, but maybe a comparison or example. I recorded at 2.7k 24fps the last time I had a long flight, here are my results.
    44995 kbps Total bitrate
    The file was automatically stopped/split at 4,103,227 KB and a second file was made.
    The 2nd file was...
    45249 kbps and 900,407 KB in size.
    AC, RC and GO on latest firmware/versions but I was not on the latest IOS at that time.
     
  6. Trackman1

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    Set video for 1080p 60fps.

    Then before you start video take 1 still image.
    Then start video. The resulting file will be 1080p 60fps 60Mbps
     
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  7. Oso

    Oso

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    FYI - You dont really need to take the still image. To get the 60Mbps on 1080/60 on a P3A, just switch it from video to still and then back to video.
     
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  8. Trackman1

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    Yes I know. Just find it easier. Plus the photo shows me where I was shooting that day. I can view the photo and click on the GPS info and google earth opens to that location.
     
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  9. GaryDZ

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    FW version 1.8.8 came out April 7th, so whatever preceded that. I am now on 1.9.6. Back when I first got the P3A I realized I was exceeding the 4GB file size limit. I was recording 1080p 60fps. So I tried 1080p 30fps.

    Here is the file info from March at 60fps
    02-21-16.jpg
    Over 18 minutes and under the 4 GB limit.

    This is on Thursday at 30fps
    08-04-16.jpg
    Only 14 minutes and video split to another file.

    I would think 30fps would take up much less space than 60fps but now that I am looking at many videos I have made it seems that the 30fps ones all have a bit rate of 40 Mbps and, therefore, create larger files. Why would that be?
     
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  10. Trackman1

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    30fps and 60fps will take up the same space unless the bitrate is changed.
    It's like chopping up a 1lb block of cheese. You can cut it up in 30 pieces or 60 pieces but you still have 1lb of cheese.

    So you chop up a second of video into 30 frames or 60 frames. It is still 1 second of video.
     
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  11. GaryDZ

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    Doesn't make sense to me. Double the number of frames (pictures, if you will) in a given time period should take up more space. That's how my feeble mind sees it. But OK. So how can I lower the bitrate?
     
  12. Trackman1

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    I know. The way you are thinking the file size would be twice as big. But it is not.

    The key words are Frames per second. So no matter if it's 30 FPS or 60 FSP it is still only one second of video.
    Frames do not increase the resolution. But more frames will make motion smoother because that 1 second of video is now made up 60 slices rather than 30.

    Increasing resolution 1080p to 2.7k will increase file size as there is more information being captured.
    Bitrate will also increase file size.
     
  13. MikeyOnline

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    Video at the same bit rate but half the FPS should have lower compression. So if you shoot 40 Mbps at 30 FPS, each frame should have fewer compression artifacts (more detail) than the same bit rate at 60 FPS. But both files would take up the same space.

    Mike