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

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!

[Josep Llobet]

Also, when calling app. variables, there is no lag. In example, in the loop:

for n = 1:100
    var_intern = [var_intern, string(n)];

    % Proba: crida a variables
    var_Josep = app.video_obj_v;

    dades_Josep = app.dades_app;
    atura_Josep = app.aturar_rep;
    video_obje_proba = app.video_obj_v;
end

The result:

But, when is changing the 'app.' variables, it makes delay:

for n = 1:100
    var_intern = [var_intern, string(n)];

    % Proba: crida a variables
    var_Josep = app.video_obj_v;

    app.dades_app = rand(1);
    app.aturar_rep = rand(1);

end

As example:

Then the best option is not use the app. as changing variables, but yes as calling non-modificable ones.

When I have no idea about app. variables, I defined all the variables in internal spaces of the app, for example in Labels and TextAreas:

Other option is define the variables in .txt files, which are a fast a reliable way.

Cheers

[Josep Llobet]

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]

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")            

Answer 1

[Josep Llobet]

True Mr!