To control the frame rate, first access the device's video source using 'getselectedsource' function and then configure the device's frame rate. Refer to the example below as a reference:
% Access an image acquisition device.
vidobj = videoinput('winvideo', 1);
% Access the device's video source and configure the device's frame rate.
% FrameRate is a device specific property, therefore, it may not be supported by
% some devices.
frameRate = 30;
src = getselectedsource(vidobj);
src.FrameRate = num2str(frameRate);
