how to use libusb--win32 to read my usbcamera?I need some help about the libusb-win32

Question

I want to use the isochronous transfer to read from my usb camera,but when i prepare to read,some problem happened. i can not read the data from my device. here is my reading-data(written in c++ by Qt) code:

{

   void* async_context = NULL;

  usb_isochronous_setup_async(handle,&async_context,0x81,64);

  usb_submit_async(async_context, recv_msg, 64);

  usb_reap_async(async_context, 1000);

  usb_free_async(&async_context);

}

and here is the message form the bus hound when i run this program:

  45.1     USTS   80000300     bad  parameter          295.1.0           2016/10/04  12:27:56.763  unknown       

maybe i use the wrong way so it does not wrok. can someone who tell me how to do it