CepstralTransform.cxx

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/*
 * Copyright (c) 2004 MUSIC TECHNOLOGY GROUP (MTG)
 *                         UNIVERSITAT POMPEU FABRA
 *
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include "CepstralTransform.hxx"
#include "OSDefines.hxx"
#include "Assert.hxx"
#include "ProcessingFactory.hxx"

namespace CLAM
{
namespace Hidden 
{
        static const char* metadata[] = {
                "key", "CepstralTransform",
                "category", "Analysis",
                "description", "CepstralTransform",
                0
        };
        static FactoryRegistrator<ProcessingFactory, CepstralTransform> reg = metadata;
}

void CepstralTransformConfig::DefaultInit()
{
        AddAll();
        UpdateData();
        SetNumMelCoefficients(20);
        SetNumCepstrumCoefficients(20);
        SetUseBase10(false);
}

CepstralTransform::CepstralTransform(  )
        : mIn("Mel Spectrum", this)
        , mOut("Mel Cepstrum", this)
{
        Configure(CepstralTransformConfig());
}

CepstralTransform::CepstralTransform( const CepstralTransformConfig& cfg )
        : mIn("Mel Spectrum", this)
        , mOut("Mel Cepstrum", this)
{
        Configure( cfg );
}

bool CepstralTransform::ConcreteConfigure( const ProcessingConfig& cfg )
{
        CopyAsConcreteConfig( mConfig, cfg );

        mLogBuffer.Resize(mConfig.GetNumMelCoefficients());
        mLogBuffer.SetSize(mConfig.GetNumMelCoefficients());

        return true;
}

bool CepstralTransform::Do()
{
        const MelSpectrum & spectrum = mIn.GetData();
        MelCepstrum & cepstrum = mOut.GetData();
        bool ok = Do(spectrum, cepstrum);
        mIn.Consume();
        mOut.Produce();
        return ok;
}

bool CepstralTransform::ConcreteStart()
{
        return true;
}

bool CepstralTransform::Do( const MelSpectrum& melSpec, MelCepstrum& melCeps )
{
        if ( !AbleToExecute() ) return false; // object was disabled

        const DataArray& melCoeffs = melSpec.GetCoefficients();
        DataArray&  cepstrumCoeffs = melCeps.GetCoefficients();
        const TSize numMelCoefficients = melCoeffs.Size();
        const TSize numCepstrumCoeffs  = mConfig.GetNumCepstrumCoefficients();

        if ( cepstrumCoeffs.Size() < numCepstrumCoeffs )
        {
                cepstrumCoeffs.Resize(numCepstrumCoeffs);
                cepstrumCoeffs.SetSize(numCepstrumCoeffs);
        }

        melCeps.SetCenterTime(melSpec.GetCenterTime());
        melCeps.SetLowCutoff(melSpec.GetLowCutoff());
        melCeps.SetHighCutoff(melSpec.GetHighCutoff());

        /* Take the logarithm of the Mel spectrum.  NOTE: What is the
                 significance of log vs. log10? */
        const TData melFloor  = 1.0;
        const bool  useBase10 = mConfig.GetUseBase10();

        if ( mLogBuffer.Size()!=numMelCoefficients)
        {
                // TODO: This has realtime penalty
                mLogBuffer.Resize(numMelCoefficients);
                mLogBuffer.SetSize(numMelCoefficients);
        }
        for (TIndex i=0; i<numMelCoefficients; i++) {
                if (melCoeffs[i] < melFloor)
                        mLogBuffer[i] = useBase10 ? log10(melFloor) : log(melFloor);
                else
                        mLogBuffer[i] = useBase10 ? log10(melCoeffs[i]) : log(melCoeffs[i]);
        }

        /* Take the DCT of the logarithm. */
        const TData piord = PI / (TData)numMelCoefficients;
        const TData scale = sqrt(2.0/(TData)numMelCoefficients);

        // Compute N-1 last coefficients.
        TData freq = 0;
        for (TIndex i=1; i<numCepstrumCoeffs; i++)
        {
                freq = i*piord;
                cepstrumCoeffs[i] = 0.0;
                for (TIndex j=0; j<numMelCoefficients; j++)
                        cepstrumCoeffs[i] += mLogBuffer[j] * cos(freq*(j+1 - 0.5));
                cepstrumCoeffs[i] *= scale;
        }

        // Compute first coefficient.
        for (TIndex j=0; j<numMelCoefficients; j++)
                cepstrumCoeffs[0] += mLogBuffer[j];
        cepstrumCoeffs[0] *= scale;


        /* NOTE: How about implementing cepstral liftering from HTK? Probably not. */

        return true;
}

}