Why do I keep getting a timeout error when I try to manually configure a webcam?

Hello,

I am trying to manually configure a webcam but keep on getting the following error:

Error using imaqdevice/getsnapshot (line 65)
A timeout occurred during GETSNAPSHOT.

Error in WebCam_Config_Test (line 17)
    snapshot = getsnapshot(vidobj);

I am running a simple test from the Mathworks site to establish whether it's feasible to use a manually configured cam. I would like to use a cam without the webcam add on, because I want to change the properties. The code I am running is below. Note that I did try to change the timeout to 500.

Does anyone have any suggestions? I would appreciate any help as this is driving me up the wall! Many thanks.

clear all;

vidobj = videoinput('macvideo', 2);
vidObj.Timeout = 500;

% 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)

% Once the video input object is no longer needed, delete the associated variable.
delete(vidobj)

Answer 1

[Vandana Rajan]

Hi,

GETSNAPSHOT is meant as a convenience function to grab one frame from a camera, and in this process, it starts the camera, takes one frame, then stops the camera. Doing this in a loop can lead to unnecessary communication with the hardware.

Instead, you may try setting a specific frame rate and TRIGGER once, then use GETDATA to access frames that are already acquired. An example code is given below.

vid = videoinput('winvideo');
triggerconfig(vid, 'manual');
vid.FramesPerTrigger = inf; 

start(vid);
trigger(vid) 

for x = 1:100
   data = getdata(vid,1); 
   % do something 
end

stop(vid);

Try this out and let us know about the outcome.

[Tasnima Rahman]

Hi Vandana,

Thank you for your reply! I tried running the code you suggested which uses "get data" rather than "get snapshot". Unfortunately, I get a whole list of errors, including a timeout error:

>> Cam_Config_Test_QAnswer
Error event occurred at 20:50:44 for video input object: YCbCr422_1280x720-macvideo-1.
Unable to allocate memory for an incoming image frame due to insufficient free physical memory.
Unable to allocate memory for an incoming image frame due to insufficient free physical
memory.

Error in imaqdevice/getdata (line 141)
        frames = getdata(imaqgate('privateGetField', obj, 'uddobject'),varargin{:});

Error in Cam_Config_Test_QAnswer (line 9)
   data = getdata(vid,1);

Error using imaqdevice/getdata (line 148)
GETDATA timed out before FRAMES were available.

Error in Cam_Config_Test_QAnswer (line 9)
   data = getdata(vid,1);

Error event occurred at 20:50:53 for video input object: YCbCr422_1280x720-macvideo-1.
GETDATA timed out before FRAMES were available.

[Vandana Rajan]

Do you have sufficient memory space available? Can you check by typing 'memory' in the MATLAB command window? Also, please see the ML Answers post given below, regarding the same error.

https://www.mathworks.com/matlabcentral/answers/103543-why-do-i-receive-the-error-getdata-timed-out-before-frames-were-available-when-using-getdata-in-im

[Tasnima Rahman]

Hi Vandana,

I tried to get memory information but my MATLAB says that the function is not available on the platform I have unfortunately. It may be because I have a student version.

I am trying some of the methods suggested in the other guides, but without much success so far.

[Vandana Rajan]

Hi Tasnima,

I have taken up this query with MathWorks Technical Support Team. Some one from the team will be reaching out to you via e-mail. Please check all your e-mail folders in case it ends up in the spam folder. Meanwhile, there is an EBR (external bug report) which is similar to your issue. Please find link for the same below

https://www.mathworks.com/support/bugreports/1422542 You may try the work around suggested in it.

[Walter Roberson]

Tasnima Rahman:

memory() is only available on MS Windows. Unfortunately on Linux and OS-X you have to look outside of MATLAB.