How to store a matrix of impulse responses in a plugin? (re: Failed to compute constant value for nontunable property)

I'm trying a build a convolver plugin that will cycle through many impulse responses. I started with the audiopluginexample.FastConvolver plugin from the Audio Plugin Example Gallery. I modified it to read in a long array of concatentated impulse responses and then split them out into a matrix to read them more easily.

When I run it in audioTestBench it works fine. When I attempt to run validateAudioPlugin I get this error:

Checking plugin class 'ggConvolv'... passed.

Generating testbench file 'testbench_ggConvolv.m'... done.

Running testbench... passed.

Generating mex file 'testbench_ggConvolv_mex.mexmaci64'... Failed to compute constant value for nontunable property 'tdiMatrix'. In code generation, nontunable properties can only be assigned constant values.

Error in ==> ggConvolv Line: 38 Column: 13

Code generation failed: View Error Report

Error using coder.internal.generateAudioPlugin

Error in validateAudioPlugin

I don't understand the issue. tdiMatrix is a constant value, right?

Of course, I immediately tried simply making tdiMatrix tunable, which just produced another error:

Checking plugin class 'ggConvolv'... passed.

Generating testbench file 'testbench_ggConvolv.m'... done.

Running testbench... passed.

Generating mex file 'testbench_ggConvolv_mex.mexmaci64'... Failed to compute constant value for nontunable property 'pNumPartitions'. In code generation, nontunable properties can only be assigned constant values.

Error in ==> ggConvolv Line: 46 Column: 13

Code generation failed: View Error Report

Error using coder.internal.generateAudioPlugin

Error in validateAudioPlugin

Here is the current state of the plugin code:

classdef (StrictDefaults)ggConvolv < audioPlugin & matlab.System
    
    properties(Nontunable)
        concatenatedTdis44 = audioread('concatenatedTdis44.wav')';
        concatenatedTdis48 = audioread('concatenatedTdis48.wav')';
        PartitionSize = 1024;
    end
    
    properties (Constant, Hidden)
        PluginInterface = audioPluginInterface(...
            'InputChannels',1,...
            'OutputChannels',1,...
            'PluginName','GainGuardian'...
            );
    end
    
    properties(Access = private, Nontunable)
        pFIR
        tdiMatrix
        currentTDIIndex = 1;
        sampleCounter = 0;
        switchSamples % Number of samples to wait before switching
        Fs
        N
    end
    
    methods(Access = protected)
        
        function setupImpl(plugin, u)
            plugin.Fs = getSampleRate(plugin);
            plugin.N = plugin.Fs / 3;
            if plugin.Fs == 44100
                concatenatedTdis = plugin.concatenatedTdis44;
            elseif plugin.Fs == 48000
                concatenatedTdis = plugin.concatenatedTdis48;
            end
            totalTdis = length(concatenatedTdis) / plugin.N;
            plugin.tdiMatrix = reshape(concatenatedTdis, plugin.N, totalTdis)';
            firstTdi = plugin.tdiMatrix(1,:);
            plugin.pFIR = dsp.FrequencyDomainFIRFilter('Numerator', firstTdi, ...
                'PartitionForReducedLatency', true, 'PartitionLength', plugin.PartitionSize);
            setup(plugin.pFIR, u);
            plugin.switchSamples = floor(11e-3 * getSampleRate(plugin)); % 11 milliseconds
            plugin.sampleCounter = 0;
            plugin.currentTDIIndex = 1;
        end
        
        function y = stepImpl(plugin,u)
            plugin.sampleCounter = plugin.sampleCounter + size(u,1);
            if plugin.sampleCounter >= plugin.switchSamples
                plugin.sampleCounter = mod(plugin.sampleCounter, plugin.switchSamples);
                plugin.currentTDIIndex = mod(plugin.currentTDIIndex, size(plugin.tdiMatrix, 1)) + 1;
                plugin.pFIR.Numerator = plugin.tdiMatrix(plugin.currentTDIIndex, :);
            end
            y = step(plugin.pFIR,u);
        end
        
        function resetImpl(plugin)
            reset(plugin.pFIR);
            setLatencyInSamples(plugin, plugin.PartitionSize);
        end
        
        function flag = isInputSizeMutableImpl(~,~)
            flag = true;
        end
        
        function s = saveObjectImpl(obj)
            s = [e-mail](obj);
            s = savePluginProps(obj,s);
            if isLocked(obj)
                s.pFIR = matlab.System.saveObject(obj.pFIR);
            end
        end
        
        function loadObjectImpl(obj, s, wasLocked)
            if wasLocked
                obj.pFIR = matlab.System.loadObject(s.pFIR);
            end
            [e-mail](obj,s,wasLocked);
            reload(obj,s);
        end
        
        %------------------------------------------------------------------
        % Propagators
        function varargout = isOutputComplexImpl(~)
            varargout{1} = false;
        end
        
        function varargout = getOutputSizeImpl(obj)
            varargout{1} = propagatedInputSize(obj, 1);
        end
        
        function varargout = getOutputDataTypeImpl(obj)
            varargout{1} = propagatedInputDataType(obj, 1);
        end
        
        function varargout = isOutputFixedSizeImpl(obj)
            varargout{1} = propagatedInputFixedSize(obj,1);
        end
    end
end

[Nathan Lively]

Moving tdiMatrix to a tunable property does seem to make sense.

properties(Access = private)
    tdiMatrix
end

Still produces this error that I don't understand: Generating mex file 'testbench_ggConvolv_mex.mexmaci64'... Failed to compute constant value for nontunable property 'pNumPartitions'. In code generation, nontunable properties can only be assigned constant values.

[Nathan Lively]

This seems to indicate that it is unable to handle some value related to the partition size. I don't understand how the impulse response that I'm introducing is any different than the impulse response introduced by a WAV file in the FastConvolver plugin example.

FastConvolver does:

ImpulseResponse = audioread('ChurchImpulseResponse-16-44p1-mono-5secs.wav').';
plugin.pFIR = dsp.FrequencyDomainFIRFilter('Numerator', plugin.ImpulseResponse, ...
    'PartitionForReducedLatency', true, 'PartitionLength', plugin.PartitionSize);

My plugin does:

concatenatedTdis44 = audioread('concatenatedTdis44.wav')';
concatenatedTdis48 = audioread('concatenatedTdis48.wav')';
plugin.Fs = getSampleRate(plugin);
plugin.N = plugin.Fs / 3;
if plugin.Fs == 44100
    concatenatedTdis = plugin.concatenatedTdis44;
elseif plugin.Fs == 48000
    concatenatedTdis = plugin.concatenatedTdis48;
end
totalTdis = length(concatenatedTdis) / plugin.N;
plugin.tdiMatrix = reshape(concatenatedTdis, plugin.N, totalTdis)';
firstTdi = plugin.tdiMatrix(1,:);
plugin.pFIR = dsp.FrequencyDomainFIRFilter('Numerator', firstTdi, ...
    'PartitionForReducedLatency', true, 'PartitionLength', plugin.PartitionSize);

[Nathan Lively]

Ah, maybe the impulse response must be divisible by the PartitionSize? But then, how would FastConvolver accept any wav file??

[Nathan Lively]

No, that didn't help. Still getting the same error about pNumPartitions.

Answer 1

[jibrahim]

Hi Nathan,

The main issue was that the code is using different filters and numerator sizes based on getSampleRate. One of the fundamental properties of audio plugins is that the sample rate is tunable. The sample rate is unknown at the time when you are generating code, and therefore you cannot rely on tnhat value to set resources such as state dimensions.

In the code below, I created separate sub-objects and local functions to handle the two sample rates of 48K and 44.1K. The generated plugin would work for either sample rate.

I also changed some properties from non-tunable to tunable because their values were being modified in stepImpl.

I am sure some of the details in the code are off and will need to be changed to work for your particular use case, but the plugin does at least pass vailidation and generation.

To test the plugin in MATLAB for different sample rates:

 g = ggConvolv;
 setSampleRate(g,48000)
 y = g(randn(1024,1); % test for 48 k)
 
  g = ggConvolv;
 setSampleRate(g,44100)
 y = g(randn(1024,1); % test for 44.1 k)

To validate and generate the plugin:

validateAudioPlugin ggConvolv
generateAudioPlugin ggConvolv

The code:

classdef (StrictDefaults)ggConvolv < audioPlugin & matlab.System

    properties(Nontunable)
        concatenatedTdis44 = randn(1,14700*100); % placeholder value
        concatenatedTdis48 = randn(1,16000*100); % placeholder value
        PartitionSize = 1024;
    end

    properties (Constant, Hidden)
        PluginInterface = audioPluginInterface(...
            'InputChannels',1,...
            'OutputChannels',1,...
            'PluginName','GainGuardian'...
            );
    end

    properties(Access = private, Nontunable)
        % Split objects - one set for each Fs
        pFIR44
        pFIR48
        tdiMatrix44
        tdiMatrix48
    end

    properties(Access = private)
        sampleCounter = 0;
        currentTDIIndex44 = 1;
        currentTDIIndex48 = 1;
        switchSamples % Number of samples to wait before switching
    end

    methods(Access = protected)

        function setupImpl(plugin, u)

            % 44100
            N = 44100 / 3;
            totalTdis = length(plugin.concatenatedTdis44) / N;
            plugin.tdiMatrix44 = reshape(plugin.concatenatedTdis44, N, totalTdis)';
            firstTdi = plugin.tdiMatrix44(1,:);
            plugin.pFIR44 = dsp.FrequencyDomainFIRFilter('Numerator', firstTdi, ...
                'PartitionForReducedLatency', true, 'PartitionLength', plugin.PartitionSize);
            setup(plugin.pFIR44, u);
            plugin.currentTDIIndex44 = 1;

            % 48000
            N = 48000 / 3;
            totalTdis = length(plugin.concatenatedTdis48) / N;
            plugin.tdiMatrix48 = reshape( plugin.concatenatedTdis48, N, totalTdis)';
            firstTdi = plugin.tdiMatrix48(1,:);
            plugin.pFIR48 = dsp.FrequencyDomainFIRFilter('Numerator', firstTdi, ...
                'PartitionForReducedLatency', true, 'PartitionLength', plugin.PartitionSize);
            setup(plugin.pFIR48, u);
            plugin.currentTDIIndex48 = 1;

            Fs = getSampleRate(plugin);
            plugin.switchSamples = floor(11e-3 * Fs); % 11 milliseconds
            plugin.sampleCounter = 0;
        end

        function y = step44(plugin,u)
            M = plugin.tdiMatrix44;
            filt = plugin.pFIR44;
            currIdx = plugin.currentTDIIndex44;
            plugin.sampleCounter = plugin.sampleCounter + size(u,1);
            if plugin.sampleCounter >= plugin.switchSamples
                plugin.sampleCounter = mod(plugin.sampleCounter, plugin.switchSamples);
                currIdx = mod(currIdx, size(M, 1)) + 1;
                filt.Numerator = M(currIdx, 1:size(filt.Numerator,2));
            end
            y = step(filt,u);
            plugin.currentTDIIndex44 = currIdx;
        end

        function y = step48(plugin,u)
            M = plugin.tdiMatrix48;
            filt = plugin.pFIR48;
            currIdx = plugin.currentTDIIndex48;
            plugin.sampleCounter = plugin.sampleCounter + size(u,1);
            if plugin.sampleCounter >= plugin.switchSamples
                plugin.sampleCounter = mod(plugin.sampleCounter, plugin.switchSamples);
                currIdx = mod(currIdx, size(M, 1)) + 1;
                filt.Numerator = M(currIdx, 1:size(filt.Numerator,2));
            end
            y = step(filt,u);
            plugin.currentTDIIndex48 = currIdx;
        end

        function y = stepImpl(plugin,u)
             Fs = getSampleRate(plugin);
            switch Fs
                case 44100
                    y = step44(plugin,u);
                case 48000
                   y = step48(plugin,u);
                otherwise
                    y = u;
                    return;
            end
        end

        function resetImpl(plugin)
            reset(plugin.pFIR44);
            reset(plugin.pFIR48);
            Fs = getSampleRate(plugin);
            plugin.switchSamples = floor(11e-3 * Fs); % 11 milliseconds
            plugin.sampleCounter = 0;
            setLatencyInSamples(plugin, plugin.PartitionSize);
        end

        function flag = isInputSizeMutableImpl(~,~)
            flag = true;
        end

        %------------------------------------------------------------------
        % Propagators
        function varargout = isOutputComplexImpl(~)
            varargout{1} = false;
        end

        function varargout = getOutputSizeImpl(obj)
            varargout{1} = propagatedInputSize(obj, 1);
        end

        function varargout = getOutputDataTypeImpl(obj)
            varargout{1} = propagatedInputDataType(obj, 1);
        end

        function varargout = isOutputFixedSizeImpl(obj)
            varargout{1} = propagatedInputFixedSize(obj,1);
        end
    end
end

[Nathan Lively]

Thanks so much! I'll test it in just a bit.

[Nathan Lively]

That worked! Afterwards I modified the code to generate the TDI library programmatically, which forced me to move tdiMatrix44 and tdiMatrix48 to properties(Access = private) since I guess they are considered tunable.

[Nathan Lively]

Hey @jibrahim may I ask one more question? Here we are prepared to handle two sample rates, 44.1 and 48kHz. Do we need to be able to handle any sample rate? If so, is can we modify this code to handle it? For example, since I am now generating the IR programmatically, can we create the matrix of IRs once at beinning in setup and then create them again any time there is a change in sample rate? Or is it a better idea to create the matrix if IRs once at the begining for every possible sample rate?

Thanks!

[Nathan Lively]

Actually, now that I think about it. I really only need to handle three sample rates, so it's not that big a deal to just handle them during setup.