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Video loses "speed" with size?

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  • Video loses "speed" with size?


    I am using a video which is started via a timer. Interval and frame rate are both set to 1, which works well when the video is small, but when I use half the screen it gets really slow.

    Is there anything I can do to avoid this?

    I use the SHORT1.WMV from one of the examples, so the short Finding Nemo scene. The file has a size of 2.5MB, so not that big.

  • #2
    The speed at which the displays draw pixels is limited by the speed at which they can be read of USD, for Picaso this is ~650,000 pixels per second, for Diablo is is ~1,220,000 pixels per second.

    Thus you can speed things up by making the video smaller.

    If you are not achieving this rate please ensure that the uSD card is formatted with the maximum cluster size and that the GCI file is not fragmented.

    Depending on the frame rate and content you can also achieve an apparent speed increase by dropping some of the frames out


    • #3
      Ok, thanks, very helpful. But how do I ensure that the GCI is not fragmented? When I look at the project folder I see two GCI files, one ends with 1 and the other with 2. Does that mean it's fragmented?


      • #4
        Goto the dos prompt and chkdsk the gci files, say

        chkdsk e:*.gci

        It will tell you if the selected files are fragmented


        • #5
          filefrag -v *.gci
          Filesystem type is: ef53
          File size of NAME~1.gci is 21471232 (5242 blocks, blocksize 4096)
          ext logical physical expected length flags
          0 0 778240 4096
          1 4096 791947 782336 1146 eof
          NAME~1.gci: 2 extents found
          File size of NAME~2.gci is 69456896 (16958 blocks, blocksize 4096)
          ext logical physical expected length flags
          0 0 800768 16958 eof
          NAME~2.gci: 1 extent found

          I guess that means, one of the files is fragemented. Is there a way in 4D systems to avoid that?


          • #6
            We just write to a file, it's windows (ultimately the device driver) that controls whether the file gets fragmented or not.

            Theoretically, starting with an empty uSD card should lead to unfragmented files, but I have seen exceptions.


            • #7
              ah ok, thanks !