Why do I get a timeout error using demoimaq_Getsnapshot?

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Aisyah Mazlan
Aisyah Mazlan 2020-3-7
回答： Harshita Gupta 2020-3-26
I'm using the example code provided in the Image Acquisition Toolbox, without changing it. However, I keep getting "Error using imaqdevice/getsnapshot (line 65). A timeout occurred during Getsnapshot".
The code is below:
%% Acquiring a Single Image in a Loop
% This example shows how to use the GETSNAPSHOT function and provides some tips for efficient use.
% The GETSNAPSHOT function allows for quick acquisition of a single video frame.
% Copyright 2006-2015 The MathWorks, Inc.
%% Set up the Acquisition Object
% Most interaction with Image Acquisition Toolbox is done through a
% video input object. These objects are created with the VIDEOINPUT
% command. This example uses a webcam that is accessed through the toolbox's
% "winvideo" adaptor.
vidobj = videoinput('winvideo');
%% Acquire a Frame
% To acquire a single frame, use the GETSNAPSHOT function.
snapshot = getsnapshot(vidobj);
% Display the frame in a figure window.
imagesc(snapshot)
%% Acquire Multiple Frames
% A common task is to repeatedly acquire a single image, process it, and
% then store the result. To do this, GETSNAPSHOT can be called in a loop.
for i = 1:5
snapshot = getsnapshot(vidobj);
imagesc(snapshot);
end
%% Timing Implications
% The GETSNAPSHOT function performs a lot of work when it is called. It
% must connect to the device, configure it, start the acquisition, acquire
% one frame, stop the acquisition, and then close the device. This means
% that the acquisition of one frame can take significantly longer than
% would be expected based on the frame rate of the camera. To illustrate
% this, call GETSNAPSHOT in a loop.
% Measure the time to acquire 20 frames.
tic
for i = 1:20
snapshot = getsnapshot(vidobj);
end
elapsedTime = toc
% Compute the time per frame and effective frame rate.
timePerFrame = elapsedTime/20
effectiveFrameRate = 1/timePerFrame
%%
% The next example illustrates a more efficient way to perform the loop.
%% Using Manual Trigger Mode
% You can avoid the overhead of GETSNAPSHOT described in the previous
% setting by using the manual triggering mode of the videoinput object.
% Manual triggering mode allows the toolbox to connect to and configure the
% device a single time without logging data to memory. This means that
% frames can be returned to MATLAB(R) with less of a delay.
% Configure the object for manual trigger mode.
triggerconfig(vidobj, 'manual');
% Now that the device is configured for manual triggering, call START.
% This will cause the device to send data back to MATLAB, but will not log
% frames to memory at this point.
start(vidobj)
% Measure the time to acquire 20 frames.
tic
for i = 1:20
snapshot = getsnapshot(vidobj);
end
elapsedTime = toc
% Compute the time per frame and effective frame rate.
timePerFrame = elapsedTime/20
effectiveFrameRate = 1/timePerFrame
% Call the STOP function to stop the device.
stop(vidobj)
%%
% You can see that the elapsed time using manual triggering is much smaller
% than the previous example.
%% Cleanup
% Once the video input object is no longer needed, delete the associated
% variable.
delete(vidobj)
I know it is not a problem with the code itself, because it's taken directly form the examples folder. The error is see is below
Error using imaqdevice/getsnapshot (line 65)
A timeout occurred during GETSNAPSHOT.
Error in demoimaq_GetSnapshot (line 16)
snapshot = getsnapshot(vidobj);
I'm using my computer camera, but I have no idea why there is an error.
Could someone help me please?

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回答（1 个）

Harshita Gupta
Harshita Gupta 2020-3-26
Hi ,
I think it may be possible that MATLAB is being blocked by anti-virus program that is installed. Apart from your anti-virus software you may also need to unblock MATLAB from Windows own anti-virus program.
Also please verify if any other application is accessing the camera and quit all the other applications that use it. Execute the "imaqreset" command in MATLAB to see if the getsnapshot works then.

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