iss video capture problem

hi,

    we use the iss model to capture video,when we capture 2336*1744 pixel from the sensor and  scaled by RSZ to 2560*1920 , the sensor output 12 fps, IPIPEIF use one-shot mode.    the problem is that, if we capture 6 fps ,the iss can work normal , but when we capturn 12 fps, the RSZ finish interrupt can't  be trigger, and the Status register show the RSZ_FIFO_OVERFLOW and RSZ_ERR , others work normal.  the ISS work at 200M clk.

  we don.t know why?  if reach the issperformance  bottleneck or the DDR bandwidth bottleneck ?