Using Image Acquisition Toolbox and Parallel processing Toolbox to display and Record a video.

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Cillian Hayde 2021-12-13

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https://ww2.mathworks.cn/matlabcentral/answers/1609695-using-image-acquisition-toolbox-and-parallel-processing-toolbox-to-display-and-record-a-video

评论： Cillian Hayde 2021-12-14

I am trying to use the image acquistion toolbox and the parallel processing toolbox to display and record a video.

Basically, I have a big while loop that is reading a serial port and performing lots of computations. When a keyword comes across the port, this starts the video recording and another ends it.

I would basically like to use the parallel processing toolbox so that the displayed image is less framey (the recorded image is actually perfect for non-parallel).

I don't have much experience with these toolbox's as its on the work license, not my personal license.

I have attached a small example of how I thought this would work. The recorded video is there in its entirety but I can't get the preview to display. Is there a technique that I am unaware of or is it fundamentally not possible?

objects = imaqfind;
delete(objects);
imaqreset;
deviceInfo = imaqhwinfo('winvideo');
poolobj = parpool(1);
spmd(1) 
    vid = videoinput('winvideo', 1, 'MJPG_640x480');
    vid.ReturnedColorspace = 'rgb';
    triggerconfig(vid, 'immediate');
    src = getselectedsource(vid);
    frameRatesAvailable = set(src, 'FrameRate');
    
    vid.FramesPerTrigger = Inf;
    vid.TriggerRepeat = Inf;
    vid.LoggingMode = 'disk';
    
    VideoDir = ""; % Directory of interest
    diskLogger = VideoWriter(VideoDir + "\TEST" + ".avi", 'Motion JPEG AVI');
    diskLogger.FrameRate = 30; % Webcam is locked at 30 fps it appears - see variable frameRatesAvailable 
    vid.DiskLogger = diskLogger;
end
% While Loop Begins
TriggerWord = "preview"; % Serial Read
pause(2)
if TriggerWord == "preview" 
    spmd(1)
      disp("Preview Run")
      preview(vid);
    end
end
pause(2);
TriggerWord = "start";% Serial Read
if TriggerWord == "start"
    spmd(1)
        disp("Start Run")
        start(vid);
    end
end
pause(2);
TriggerWord = "stop";% Serial Read
if TriggerWord == "stop"
    spmd(1)
        disp("Stop Run")
        stop(vid);
    end
end
pause(2);
TriggerWord = "closepreview";% Serial Read
if TriggerWord == "closepreview"
    spmd(1)
        disp("Close Preview Run")
        closepreview(vid);
    end
end
% While Loop Ends
delete(poolobj)

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Raymond Norris 2021-12-13

This issue is that the preview is running on a "headless" worker (within the spmd block), without access to a display. Perhaps you could queue data to the client to display, but I can't imagine you'd get the refresh updates that you'd want.

Cillian Hayde 2021-12-14

@Raymond Norris, Thank you for your reply and introducing me to the concept of a headless worker!

It appears I can't mark your comment as resolving my issue even though I feel it has (The forum doesn't allow it).

Thank you for your time!

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