taking input from two cameras at a same time in Matlab

how can i use and take input from two cameras at the same time?

Answer 1

[David Tarkowski]

In general working with two cameras is the same as working with a single camera. You create a videoinput object for each device that you wish to capture from and the call start on each device:

vid1 = videoinput('winvideo', 1);
vid2 = videoinput('winvideo', 2);
start([vid1 vid2]);

These devices will be started at roughly the same time, but will not by synchronized due to delays imposed by the operating system and drivers in actually starting them. To synchronize multiple devices precisely, you generally need to use devices that support hardware triggering.

[Tiago]

I have the same problem.

I'm able to preview each webcam separately but when I try to preview both I get this error:

    Error using imaqdevice/preview (line 177)
    The image acquisition device failed to start acquiring images.

This is my code (it only previews vid1):

vid1 = videoinput('linuxvideo',1);
vid2 = videoinput('linuxvideo',2);

subplot(211)
h1 = image;
preview(vid1,h1)

subplot(212)
h2 = image;
preview(vid2,h2)

[Image Analyst]

What's with the "h=image" line? image() is a function that takes an array as an argument, and you didn't supply anything.

[Tiago]

my bad, but even something as simple as:

    vid1 = videoinput('linuxvideo',1);
    vid2 = videoinput('linuxvideo',2);
    preview(vid1)
    preview(vid2)

will give the same error.

Any advice on previewing two cameras?

[Image Analyst]

You need to give it a handle to an image object:

axes(handles.axes1);
handleToImageInAxes1 = image(zeros(800,600));
% Turn on the live video.
preview(vidobj, handleToImageInAxes1);
axes(handles.axes2);
handleToImageInAxes2 = image(zeros(800,600));
% Turn on the live video.
preview(vidobj, handleToImageInAxes2);

[Tiago]

I did like this:

    vid1 = videoinput('linuxvideo',1);
    vid2 = videoinput('linuxvideo',2);

    handles.axes1 = subplot(1,2,1);
    axes(handles.axes1);
    handleToImageInAxes1 = image(zeros(800,600));
    preview(vid1, handleToImageInAxes1);

    handles.axes2 = subplot(1,2,2);
    axes(handles.axes2);
    handleToImageInAxes2 = image(zeros(800,600));
    preview(vid2, handleToImageInAxes2);

and still the same error at the second preview. Any idea?

Answer 2

[Hassan Mehmood Khan]

i did this to get snapshot from two cams at same time:

% webcamlist identification
clc;
clearvars;

webcamlist

cam=webcam;
cam2=webcam(2);

cam.AvailableResolutions;
cam2.AvailableResolutions;

cam.Resolution='640x480';
cam2.Resolution='640x480';

% preview(cam);
% preview(cam2);

img=snapshot(cam);
img2=snapshot(cam2);
img3=snapshot(cam);
img4=snapshot(cam2);

figure;
subplot(3,3,1);
imshow(img3);
subplot(3,3,2);
imshow(img4);

output

ans = 

      'Webcam C170'
      'Logitech HD Webcam C270'

[Thao Pham]

It work, thank you

Answer 3

[Andrei]

Also refer to the following example which uses Parallel Computing Toolbox with Image Acquisition Toolbox

https://www.mathworks.com/matlabcentral/answers/388286-how-can-i-acquire-images-from-multiple-gige-cameras-using-image-acquisition-toolbox-and-parallel-com

Answer 4

[Walter Roberson]

See http://www.mathworks.com/matlabcentral/answers/5993-capture-from-multiple-webcams