MATLAB: “Preview Vid” doesn’t work properly after compiling into standalone executable

applicationcompilerguiimage acquisitionImage Acquisition Toolboxpreviewstandalonevideo

I have written a GUI to show four live video streams from HD webcams (Logitech C920). When I run my GUI in MATLAB, it functions flawlessly, press the "Preview" pushbutton and it detects if there are 1-4 cameras and displays their live images in axes in the GUI. After compiling to a standalone executable using the Compiler Application, when the "Preview" pushbutton is pressed, it shows 1 fewer cameras then the number selected, and it doesn't show a live stream, just a still of the first frame they see. The rest of the code seems to function properly (all cameras continue to record after I hit the "Begin" pushbutton. Below is the code for the "Preview" pushbutton (please disregard the sad nested if loop in the for loop, that was a bit of a workaround for an issue I was seeing earlier).
function Preview_Callback(hObject, ~, handles)
% hObject    handle to Preview (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
handles.TLI = ceil(handles.expLengthMin/300); %Time between images (timelapse interval)
handles.fileName = [date,'_',handles.Manufacturer,'_',handles.Bandage];
for i=1:handles.numCamera
    handles.vid(i) = videoinput('winvideo', i, 'RGB24_1920x1080'); %Video Format
    handles.src(i) = getselectedsource(handles.vid(i));
    handles.src(i).FrameRate = '5.0000'; %Frame rate
    handles.src(i).FocusMode = 'manual'; %Focus mode
    handles.src(i).Focus = 50;% Focus length for glass cylinder
    handles.frameRate = str2double(handles.src(i).FrameRate);
    handles.vid(i).FramesPerTrigger = handles.expLengthMin/handles.TLI;
    handles.vid(i).FrameGrabInterval = (handles.frameRate*60)*handles.TLI;
    handles.vid(i).LoggingMode = 'disk';
    docname = [handles.fileName,'_#',num2str(i),'.avi'];
    handles.diskLogger = VideoWriter(docname, 'Uncompressed AVI');
    handles.diskLogger.FrameRate = 60/handles.TLI;
    handles.vid(i).DiskLogger = handles.diskLogger;
end
vidRes = handles.vid(1).VideoResolution;
nBands = handles.vid(1).NumberOfBands;
for i=1:handles.numCamera
    if i == 1;
        h(1) = image(zeros(vidRes(2),vidRes(1),nBands),'Parent',handles.axes1);
        preview(handles.vid(1),h(1))
    elseif i == 2;
        h(2) = image(zeros(vidRes(2),vidRes(1),nBands),'Parent',handles.axes2);
        preview(handles.vid(2),h(2))
    elseif i == 3;
        h(3) = image(zeros(vidRes(2),vidRes(1),nBands),'Parent',handles.axes3);
        preview(handles.vid(3),h(3))
    elseif i == 4;
        h(4) = image(zeros(vidRes(2),vidRes(1),nBands),'Parent',handles.axes4);
        preview(handles.vid(4),h(4))
    end
end
guidata(hObject,handles);

Best Answer

Seems like a bug to me. To work around the issue, make sure that the main function does not end before the whole application does; you can use the "waitfor" function to accomplish this.
For example if you have a GUIDE GUI myGUI, where somewhere in the callback of this GUI "preview" is actually called, and you used to compile myGUI into myGUI.exe you can work around the issue by writing the following function:
function myMain
  waitfor(myGUI)
Use myMain.m as the main function for your standalone.
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