VERY SLOW aqcuisition of video frames using snapshot function compared to windows camera

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Mario Trevino 2017-8-16

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https://ww2.mathworks.cn/matlabcentral/answers/353002-very-slow-aqcuisition-of-video-frames-using-snapshot-function-compared-to-windows-camera

评论： Augusto Sanches 2019-2-13

Im trying to acquire videos using Matlab and Microsoft webcam with maximum resolution, yet the effective sampling frequency is extremely slow (one order of magnitude) compared to what I can get using conventional recording with the windows program 'camera'. Any ideas???? ( I do have many advantages of being able to to the whole process through MATLAB but need a decent speed though).

The core of my code looks like this:

cam = webcam(1);
cam.Resolution='1920x1080';
cam.WhiteBalance=3000;  % 2500 to 10000
cam.Exposure=-13;        % 0 to -13
cam.Brightness=30;      % 30 to 255   VALOR USADO 160
cam.Sharpness=50;        % 0 to 50
cam.Focus=30;            % 0 to 40
cam.Contrast=5;        % 0 to 10
cam.BacklightCompensation=0; % 0 to 10
cam.Saturation=0;    % 0 to 200
cam.Zoom=0; %0 to 317
fileobj_save = VideoWriter(filename_save); 
open(fileobj_save)
while tElapsed<=max_time
f=snapshot(cam);
writeVideo(fileobj_save,f);
end
close(fileobj_save)

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Augusto Sanches 2019-2-13

Hello, Mario!

I was facing the same issue with the snapshot function. So I downloaded and installed this toolbox:

https://www.mathworks.com/matlabcentral/fileexchange/45183-image-acquisition-toolbox-support-package-for-os-generic-video-interface

This will give you access to the 'winvideo' adaptor. So I used imaqhinfo('winvideo') and found the video input constructor of my camera. Using this constructor of your camera, you can start acquiring images using the getSnapshot function. This function worked a way faster for me.

Here they show you how to use the getSnapshot function:

https://www.mathworks.com/help/imaq/examples/acquiring-a-single-image-in-a-loop.html

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