7 Replies Latest reply on May 28, 2012 9:54 PM by andy.yao

    the speed of PC processing UVC data is too low???

    andy.yao

      hello!everybody !

         

       I successfully finished  transfering YUV -format data in UVC BULK mode on cypress FX3,I tested the data transfering speed by printing the DMA buf counts per second ,and it almostly  reach to 200MB/S more.

         

      args:

         

       max burst size  = 16

         

      DMA BUF size = 16*1024

         

      DMA BUF counts = 10

         

      however,the frame rate is far away from the theoretical value,I watched the frame rate using debut capture,and framerate is at most up to 10fps when the resolution is 2592x1944, namely,the actual speed at PC is less than 100MB/S.  then I changed the args to test,and when DMA BUF size = 6*1024,the speed is about 100MB/S,and framerate can be up to 10fps when the resolution is 2592x1944.  even when the DMA BUF size = 32*1024, DMA BUF counts = 5 ,framerate is still   10fps when the resolution is 2592x1944.  but  the  data transfering speed can be up to 250MB/S .

         

      so I  guess that the speed of PC processing UVC data is too low!   Maybe it's restricted by UVC driver or decoder or something else!

         

      at last, I wanna improve the speed by using BULK stream protocol,but it failed ! (it can start the mulitiple DMA channels to transfer datas,but the speed is always about 7MB/S,and the data size every times is always 1024B) I referred the example  cyfxbulkstreams in FX3 SDK, I dont know whether UVC bulk mode can support the stream protocol!  can anyone tell me the answer?

         

      thx! and sorry for my mistakes and unclear expressiong!