Why MATLAB App is standstill, collapse, when a video is executed and processed?

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Josep Llobet 2022-12-22

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1883322-why-matlab-app-is-standstill-collapse-when-a-video-is-executed-and-processed

编辑： Josep Llobet 2023-4-9

采纳的回答： Josep Llobet

在 MATLAB Online 中打开

Why when execute a MATLAB App with different functions it collapse, saturate, standstill?

I think it is because the internal app variables (app.variable).

I would like to auto-respond my question with the next example.

I create an app which, given a video object (you can obtain it by: videoObject = VideoReader(video_rute)), execute a frame to frame:

When you click pause, the video stops.

The execution button have a loop that show every frame for every step, working correctly.

    app.aturar_rep = false;
    
    for frame = 1:app.video_obj_v.NumFrames
        imgFrame = read(app.video_obj_v, frame);
        app.Image.ImageSource = imgFrame;
        if app.aturar_rep % to stop
            break
        end
    end

Then, if we put an internal variable to re-define while executing the loop, the program collapse, and makes it go slower.

Here the example is in the variable app.dades_app

        app.aturar_rep = false;
    
    var_intern = [];
    for frame = 1:app.video_obj_v.NumFrames
        imgFrame = read(app.video_obj_v, frame);
        app.Image.ImageSource = imgFrame;
        if app.aturar_rep
            break
        end
 
         for n = 1:100
             app.dades_app = [app.dades_app, string(n)];
         end
    end
    

I show you, even in the first frame the program collapse:

And I need to Ctrl+C to re- run it.

Then, if we use a non-internal variable, this does not occurs (variable var_intern) :

        app.aturar_rep = false;
    
    var_intern = [];
    for frame = 1:app.video_obj_v.NumFrames
        imgFrame = read(app.video_obj_v, frame);
        app.Image.ImageSource = imgFrame;
        if app.aturar_rep
            break
        end
 
         for n = 1:100
             var_intern = [var_intern, string(n)];
         end
    end

I show you:

Then we have identifyied the standstill reason of MATLAB App, which mainly is the use of the App internal variables (app.variable_ex) (which are useful, but in this case dificult us).

Thank you!

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Josep Llobet 2022-12-29

编辑：Josep Llobet 2022-12-29

在 MATLAB Online 中打开

Same time, if we generate the change of a internal object, there is no delay unless we change it too much fast

Code exampel:

        for n = 1:100
            var_intern = [var_intern, string(n)];
            randomstr = [string(char(randi([33 126],1,10))), string(char(randi([33 126],1,10))), string(char(randi([33 126],1,10))), string(char(randi([33 126],1,10))), string(char(randi([33 126],1,10))), string(char(randi([33 126],1,10))), string(char(randi([33 126],1,10))), string(char(randi([33 126],1,10)))];            
        end
        
        app.ListBox.Items = randomstr;

Josep Llobet 2022-12-29

在 MATLAB Online 中打开

If we generate a Axis changing, is the same, it will standstill in order of our upgrade.

for n = 1:100
    var_intern = [var_intern, string(n)];
end
    xline(app.UIAxes, [rand(1)], "Color", "c")            

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Answer 1

Josep Llobet 2022-12-22

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1883322-why-matlab-app-is-standstill-collapse-when-a-video-is-executed-and-processed#answer_1134462

True Mr!

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