MFCC extractor: Index was outside the bounds of the array

[stefanpantic]

I am getting the following exception when I try to compute MFCC on my .wav file.

System.IndexOutOfRangeException: Index was outside the bounds of the array.
   at NWaves.Transforms.Dct4.Direct(Single[] input, Single[] output)
   at NWaves.FeatureExtractors.MfccExtractor.ProcessFrame(Single[] block)
   at NWaves.FeatureExtractors.Base.FeatureExtractor.ComputeFrom(Single[] samples, Int32 startSample, Int32 endSample)
   at MFCC.Example.Main(String[] args) in /home/stefan/Documents/work/ls_records/mfcc/WavMFCC/Program.cs:line 58

Here's my code where I construct the extractor.

        private static readonly MfccExtractor MfccExtractor = new MfccExtractor(
            16000,
            32,
            0.025,
            0.01,
            fftSize: 1024,
            preEmphasis: 0.97,
            includeEnergy:true,
            dctType: "4",
            nonLinearity:NonLinearityType.LogE);

Changing the feature count from 32 to a smaller number, say 13 passes and doesn't throw the exception.

[ar1st0crat]

Hi! Dct in MFCC is used for compressing data (dimensionality reduction similar to PCA). So it makes no sense to specify number of coefficients bigger than number of mel filters. If you need 32 coeffs for some reason, then make sure the filterbankSize >= 32.

[stefanpantic]

Thanks :D