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How to optimize software performance on high frame rates on USB3.0 cameras?

In order to receive all images in case of high frame rate and/or small height of image (ROI) is used - it is necessary to:
  • increase value of XI_PRM_BUFFERS_QUEUE_SIZE
  • decrease value of XI_PRM_ACQ_TRANSPORT_BUFFER_SIZE

See xiAPI Manual for details.

Simplified implementation example

Example of initialization code:

#define HandleResult(res,place) if (res!=XI_OK) {printf("Error after %s (%d)\n",place,res);goto finish;}
stat = xiOpenDevice(0, &xiH);

// set ROI height
int height=200;
stat = xiSetParamInt(xiH, XI_PRM_HEIGHT, height);
HandleResult(stat,"xiSetParam (height)");
int payload=0;
stat = xiGetParamInt(xiH, XI_PRM_IMAGE_PAYLOAD_SIZE, &payload);
HandleResult(stat,"xiGetParam (payload)");

// ---------------------------------------------------
// select transport buffer size depending on payload

int transport_buffer_size_default = 0;
int transport_buffer_size_increment = 0;
int transport_buffer_size_minimum = 0;
// get default transport buffer size - that should be OK on all controllers
stat = xiGetParamInt(xiH, XI_PRM_ACQ_TRANSPORT_BUFFER_SIZE, &transport_buffer_size_default);
HandleResult(stat,"xiGetParamInt (transport buffer size)");
stat = xiGetParamInt(xiH, XI_PRM_ACQ_TRANSPORT_BUFFER_SIZE XI_PRM_INFO_INCREMENT, &transport_buffer_size_increment);
HandleResult(stat,"xiGetParamInt (transport buffer size increment)");
stat = xiGetParamInt(xiH, XI_PRM_ACQ_TRANSPORT_BUFFER_SIZE XI_PRM_INFO_MIN, &transport_buffer_size_minimum);
HandleResult(stat,"xiGetParamInt (transport buffer size minimum)");

// check if payload size is less than default transport buffer size
if(payload < transport_buffer_size_default + transport_buffer_size_increment)
    // use optimized transport buffer size, as nearest increment to payload
    int transport_buffer_size = payload;
    if (transport_buffer_size_increment)
        // round up to nearest increment
        int remainder = transport_buffer_size % transport_buffer_size_increment;
        if (remainder)
            transport_buffer_size += transport_buffer_size_increment - remainder;
    // check the minimum
    if (transport_buffer_size < transport_buffer_size_minimum)
        transport_buffer_size = transport_buffer_size_minimum;
    stat = xiSetParamInt(xiH, XI_PRM_ACQ_TRANSPORT_BUFFER_SIZE, transport_buffer_size);
    HandleResult(stat,"xiSetParam (transport buffer size)");

// ---------------------------------------------------
// set maximum number of queue
int number_of_field_buffers = 0;
xiGetParamInt(xiH, XI_PRM_BUFFERS_QUEUE_SIZE XI_PRM_INFO_MAX, &number_of_field_buffers);
HandleResult(stat,"xiGetParam (number_of_field_buffers maximum)");
xiSetParamInt(xiH, XI_PRM_BUFFERS_QUEUE_SIZE, number_of_field_buffers);
HandleResult(stat,"xiSetParam (number_of_field_buffers)");


// getting images in loop