VST creation: Index in position 1 is invalid

Everything works properly in audioTestBench but I get "Index in position 1 is invalid" error when I try to export my audio plugin. Thanks for any help...

classdef reverser2 < audioPlugin
    properties
        dry = 0.5;
        wet = 0.5;
        size = 1;  
        twriteBuffer = 1;  % start writing from buffer 1 (and reading on buffer 2)
    end
    properties (Access = private)
        tBuffera = zeros(176400,2);
        tBufferb = zeros(176400,2);
        BufferIndex = 1;
        NSamples = 44100;
    end
    properties (Constant)
        PluginInterface = audioPluginInterface(...
            audioPluginParameter('dry',...
            'DisplayName','Dry',...
            'Mapping',{'lin',0,1}),...          
            audioPluginParameter('wet',...
            'DisplayName','Wet',...
            'Mapping',{'lin',0,1}),... 
            audioPluginParameter('size',...    
            'DisplayName','Buffer size',... 
            'Mapping',{'lin',0.1,4},...    
            'Label','seconds'))                 
    end
    methods
        function out = process(plugin, in)
            out = zeros(size(in));
            writeIndex = plugin.BufferIndex; % set writing point (last sample read)
            readIndex = plugin.NSamples - writeIndex; % set reading point (mirrored point of the writing)
            who = plugin.twriteBuffer;
            % plugin.CircularBuffer=flipud(plugin.CircularBuffer);
            if readIndex <= 0
                readIndex = readIndex + plugin.NSamples;
            end
            
            for i = 1:size(in,1)
                if who == 1
                    plugin.tBuffera(writeIndex,:) = in(i,:);
                    reverse = plugin.tBufferb(readIndex,:);
                else
                    plugin.tBufferb(writeIndex,:) = in(i,:);
                    reverse = plugin.tBuffera(readIndex,:);
                end
                out(i,:) = in(i,:)*plugin.dry + reverse*plugin.wet;
                
                writeIndex = writeIndex + 1;  % move forward the writing point
                if writeIndex > plugin.NSamples
                    writeIndex = 1;
                end
                
                readIndex = readIndex - 1; % move backward the reading point
                if readIndex <= 0
                    readIndex = plugin.NSamples;
                    if who == 1
                        who = 2;
                    else
                        who = 1;    
                    end
                end
            end
            plugin.BufferIndex = writeIndex;
            plugin.twriteBuffer = who;
        end
        function set.size(plugin, val)                         
            plugin.size = val;                                 
            plugin.NSamples = floor(getSampleRate(plugin)*val);
        end  
    end
end

[Florian Bidaud]

On which line do you get this error ?

[Tommaso]

is there a way to know it?

Because I get it when I click on export as a generic dialog window.

Answer 1

[jibrahim]

I assume you get an error when you attempt to generate an audio plugin.

I can reproduce your error if I validate the audio plugin:

validateAudioPlugin reverser2

You will see the error coming from line 41. The index readIndex is negative.

You should be able to debug your code by following the errors from validateAudioPlugin. Use common debugging tools to put breakpoints on the offending line of your code.

[Tommaso]

thanks for the advice in debugging. Still struggling on why a got a negative index value.