MATLAB: PCompiledNumChannels error in audio plugin generation

audioAudio ToolboxMATLAB Compilerplugin

Hi
I´m trying to use crossoverFilter function as part of a more elaborated signal process plugin, but I find the following error message when I try to generate the audio plugin:
"Failed to compute constant value for nontunable property 'pCompiledNumChannels'. In code generation,nontunable properties can only be assigned constant values".
No issues at all when I run it through audioTestBench, but it does when I try to compile.
The code is really long, but as an example, I reproduce the same with a basic code attached. So, even when this one is not useful at all, I think help to reproduce the error easily.
classdef (StrictDefaults)CrossTest < matlab.System & audioPlugin
% CrossOver plugin test
    properties        
        FCross=100;
    end
    
    properties (Constant, Hidden)
        % Define the plugin interface
        PluginInterface = audioPluginInterface( ...
            'InputChannels',2,...
            'OutputChannels',2,...
            'PluginName','CrossOver Test',...
            audioPluginParameter('FCross', ...
            'DisplayName',  'Frequency Cutoff', ...
            'Mapping', { 'int', 20, 18000}, ...
            'Style', 'rotaryknob'))
    end    
    
    properties (Access = private)    
        xFilt;
        NumCrossovers = 1;
        hpf;
        pSR;
    end
    
    methods
        % Constructor
        function plugin = CrossTest 
            
            fs = getSampleRate(plugin);
            plugin.xFilt=crossoverFilter("SampleRate",fs,"NumCrossovers",1,"CrossoverFrequencies",100,"CrossoverSlopes",6);
            plugin.hpf=dsp.HighpassFilter('FilterType','IIR','PassbandFrequency',300,'StopbandFrequency',100,'StopbandAttenuation',40);                     % <<--- Agregado
            
        end
        
        function set.FCross (plugin,val)
            plugin.FCross=val;
            plugin.crossdesign;
        end
        
    end
    methods(Access = protected)
 %% OUT
        function out = stepImpl(plugin, in)
           
            infilt=plugin.hpf(in); % Filter the input signal
            [O1,O2]=plugin.xFilt(infilt); % CrossOver the filtered Signal
              
            out=O1+O2;
          end
        function resetImpl(plugin)
            reset(plugin.xFilt);
        end
     
    end
        
    methods (Access = private)
        function crossdesign(plugin)
            plugin.xFilt.CrossoverFrequencies=plugin.FCross;
        end        
       
    end
    
end
I would really appreciate if someone give me a hint about how to overcome this.
Thanks
Pablo

Best Answer

Hi Pablo,
The corssover filter object is complaining that the number of channels is unknown. This is because the code generation compiler interprets the input to the crossover as having a varying 2nd dimension.
Modify the call to your crossover in stepImpl to this:
[O1,O2]=plugin.xFilt(infilt(:,1:2)); % CrossOver the filtered Signal
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