Index exceeds the number of array elements (480)

Error occurs when attemping to validate the plugin

classdef modDelay < audioPlugin
    
    properties
        
        Depth = 0.004;  % Range(0.001,0.007)
        Rate = 0.6;     % Range(0.1,20)
        feedback = 0.5;
        
    end
    
    properties (Access = private)
        
        modDelayLineL = zeros(round(0.01*48000),1);
        modDelayLineR = zeros(round(0.01*48000),1);
        
        modIdxL = 1;
        modIdxR = 1;
        
        phase = 0;
        
    end
    
    properties (Constant)
        
        
        
    end
    
    methods
        
        function out = process(plugin,in)
            
            L = length(in);
            out = zeros(L,2);
            
            Fs = getSampleRate(plugin);
            T = 1/Fs;
            
            for n = 1:L
                
                modReadIdxL = plugin.modIdxL + round(abs(round(plugin.Depth*Fs)*...
                    sin(plugin.phase)));
                modReadIdxR = plugin.modIdxR + round(abs(round(plugin.Depth*Fs)*...
                    sin(plugin.phase)));
                
                % Left Channel Read Index
                if modReadIdxL > round(0.01*Fs)
                    modReadIdxL = modReadIdxL - round(0.01*Fs);
                end
                % Right Channel Read Index
                if modReadIdxR > round(0.01*Fs)
                    modReadIdxR = modReadIdxR - round(0.01*Fs);
                end
                
                % Increment the phase of control sinusoid
                plugin.phase = plugin.phase + 2*pi*plugin.Rate*T;
                % Wrap phase around 2*pi
                if(plugin.phase > 2*pi)
                    plugin.phase = plugin.phase - 2*pi;
                end
                
                % Write to Output
                out(n,1) = plugin.modDelayLineL(modReadIdxL);
                out(n,2) = plugin.modDelayLineR(modReadIdxR);
                
                % Write to Delay Lines
                
                % Left Channel Delay
                plugin.modDelayLineL(plugin.modIdxL) = in(n,1) +...
                    plugin.feedback*plugin.modDelayLineL(modReadIdxL);
                
                % Right Channel Delay
                plugin.modDelayLineR(plugin.modIdxR) = in(n,2) +...
                    plugin.modDelayLineR(modReadIdxR);
                
                % Increment Modulation Index Values
                plugin.modIdxL = plugin.modIdxL + 1;  % Left Channel
                plugin.modIdxR = plugin.modIdxL + 1;  % Right Channel
                
                % Wrap Index Values Around to Create a Circular Buffer
                
                % Left Channel
                if plugin.modIdxL > round(0.01*Fs)
                    plugin.modIdxL = 1;
                end
                % Right Channel
                if plugin.modIdxR > round(0.01*Fs)
                    plugin.modIdxR = 1;
                end
                
            end
            
            function reset(plugin)
                
                plugin.modDelayLineL = zeros(round(0.01*48000),1);
                plugin.modDelayLineR = zeros(round(0.01*48000),1);
                
                plugin.modIdxL = 1;
                plugin.modIdxR = 1;
                
                plugin.phase = 0;
                
            end
            
        end
        
    end
    
end

[KALYAN ACHARJYA]

Please refer: There are so many common threads with the same issue

https://www.mathworks.com/matlabcentral/answers/441852-index-exceeds-the-number-of-array-elements

[Nathanael Channings]

Unfortunately none of them refer to the use of the audio toolbox, this makes drawing comparisons rather difficult.

[jibrahim]

Hi Nathanael,

validateAudioPlugin will run a testbench against your plugin. You can use the keeptestbench option to preserve the testbench m file:

validateAudioPlugin -keeptestbench modDelay

To reproduce the error, just run testbench_modDelay. You can put breakpoints in that file to hopefully give you insight into what is going wrong.

[Nathanael Channings]

Thank you for your suggestion jibrahim, the problem seems to be caused by calling the...

getSampleRate(plugin) % Function

Where the sample rate seems to change from 48000 to 96000 inexplicably, defining the sample rate as a constant 48000 seems to have solved the issue so far.

Answer 1

[jibrahim]

Hi Nathanael,

I took a look at the code. I saw two issues:

a. There seems to be a misplaced end that was making the reset method unreachable

b. In reset, instead of 48e3, I use getSampleRate to get the sample rate.

Note that reset is called automatically when the sample rate changes

With these changes, it seems validateAudioPlugin works.

classdef modDelay < audioPlugin
    
    properties
        
        Depth = 0.004;  % Range(0.001,0.007)
        Rate = 0.6;     % Range(0.1,20)
        feedback = 0.5;
        
    end
    
    properties (Access = private)
        
        modDelayLineL = zeros(round(0.01*48000),1);
        modDelayLineR = zeros(round(0.01*48000),1);
        
        modIdxL = 1;
        modIdxR = 1;
        
        phase = 0;
        
    end
    
    properties (Constant)
        
        
        
    end
    
    methods
        
        function out = process(plugin,in)
            
            L = length(in);
            out = zeros(L,2);
            
            Fs = getSampleRate(plugin);
            T = 1/Fs;
            
            for n = 1:L
                
                modReadIdxL = plugin.modIdxL + round(abs(round(plugin.Depth*Fs)*...
                    sin(plugin.phase)));
                modReadIdxR = plugin.modIdxR + round(abs(round(plugin.Depth*Fs)*...
                    sin(plugin.phase)));
                
                % Left Channel Read Index
                if modReadIdxL > round(0.01*Fs)
                    modReadIdxL = modReadIdxL - round(0.01*Fs);
                end
                % Right Channel Read Index
                if modReadIdxR > round(0.01*Fs)
                    modReadIdxR = modReadIdxR - round(0.01*Fs);
                end
                
                % Increment the phase of control sinusoid
                plugin.phase = plugin.phase + 2*pi*plugin.Rate*T;
                % Wrap phase around 2*pi
                if(plugin.phase > 2*pi)
                    plugin.phase = plugin.phase - 2*pi;
                end
                
                % Write to Output
                out(n,1) = plugin.modDelayLineL(modReadIdxL);
                out(n,2) = plugin.modDelayLineR(modReadIdxR);
                
                % Write to Delay Lines
                
                % Left Channel Delay
                plugin.modDelayLineL(plugin.modIdxL) = in(n,1) +...
                    plugin.feedback*plugin.modDelayLineL(modReadIdxL);
                
                % Right Channel Delay
                plugin.modDelayLineR(plugin.modIdxR) = in(n,2) +...
                    plugin.modDelayLineR(modReadIdxR);
                
                % Increment Modulation Index Values
                plugin.modIdxL = plugin.modIdxL + 1;  % Left Channel
                plugin.modIdxR = plugin.modIdxL + 1;  % Right Channel
                
                % Wrap Index Values Around to Create a Circular Buffer
                
                % Left Channel
                if plugin.modIdxL > round(0.01*Fs)
                    plugin.modIdxL = 1;
                end
                % Right Channel
                if plugin.modIdxR > round(0.01*Fs)
                    plugin.modIdxR = 1;
                end
                
            end
            
        end
        function reset(plugin)
            
            Fs = getSampleRate(plugin);
            plugin.modDelayLineL = zeros(round(0.01*Fs),1);
            plugin.modDelayLineR = zeros(round(0.01*Fs),1);
            
            plugin.modIdxL = 1;
            plugin.modIdxR = 1;
            
            plugin.phase = 0;
            
        end
        
    end
    
end