how to display spectrogram of a audio in App Designer

Question

austin austin 2018-10-3

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https://ww2.mathworks.cn/matlabcentral/answers/422011-how-to-display-spectrogram-of-a-audio-in-app-designer

评论： Edgar Guevara 2018-10-4

I want show the figure in the app designer interface.But did not success.I only can plot it outside of app designer.I am using Matlab 2018b.

spectrogram(audio,window,noverlap,nfft,fs,'yaxis');

Anyone know how to do it. Thanks.

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Answer 1

Edgar Guevara 2018-10-3

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Dear Austin,

You need to specify which axes will be used for plotting, inside a callback for plotting such spectrogram, you may use the following example code:

t = 0:0.001:2;
x = chirp(t,100,1,200,'quadratic');
myAxe = app.UIAxes;
[S,F,T] = spectrogram(x,128,120,128,1e3);
imagesc(myAxe, T, F, log(1+abs(S)) ); %plot the log spectrum
set(myAxe,'YDir', 'normal'); % flip the Y Axis so lower frequencies are at the bottom

Let me know if that solves your problem.

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austin austin 2018-10-3

By the way, the way you did, it is work good. But the spectrogram color is a little darker. Is there any way can make it brighter? Thank you.

Edgar Guevara 2018-10-4

I think your spectrogram is not displayed on log scale, try the following code, which reproduces the output from the built-in function:

    methods (Access = private)
        % Button pushed function: Button
        function plotSpec(app, event)
            t = 0:0.001:2;
            x = chirp(t,100,1,200,'quadratic');
            myAxe = app.UIAxes;
            [S,F,T] = spectrogram(x,128,120,128,1e3);
            imagesc(myAxe, F, T, log(abs(S'))); %plot the log spectrum
            set(myAxe,'YDir', 'normal'); % flip the Y Axis so lower frequencies are at the bottom 
            axis square 
            axis tight
            colorbar
        end
    end