view data/model/WaveformOversampler.h @ 1833:21c792334c2e sensible-delimited-data-strings

Rewrite all the DelimitedDataString stuff so as to return vectors of individual cell strings rather than having the classes add the delimiters themselves. Rename accordingly to names based on StringExport. Take advantage of this in the CSV writer code so as to properly quote cells that contain delimiter characters.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
   
    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.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef SV_WAVEFORM_OVERSAMPLER_H
#define SV_WAVEFORM_OVERSAMPLER_H

#include "base/BaseTypes.h"

class DenseTimeValueModel;

/** Oversample the sample data from a DenseTimeValueModel by an
 *  integer factor, on the assumption that the model represents
 *  audio. Oversampling is carried out using a windowed sinc filter
 *  for a fixed 8x ratio with further linear interpolation to handle
 *  other ratios. The aim is not to provide the "best-sounding"
 *  interpolation, but to provide accurate and predictable projections
 *  of the theoretical waveform shape for display rendering without
 *  leaving decisions about interpolation up to a resampler library.
 */
class WaveformOversampler
{
public:
    /** Return an oversampled version of the audio data from the given
     *  source sample range. Will query sufficient source audio before
     *  and after the requested range (where available) to ensure an
     *  accurate-looking result after filtering. The returned vector
     *  will have sourceFrameCount * oversampleBy samples, except when
     *  truncated because the end of the model was reached.
     */
    static floatvec_t getOversampledData(const DenseTimeValueModel &source,
                                         int channel,
                                         sv_frame_t sourceStartFrame,
                                         sv_frame_t sourceFrameCount,
                                         int oversampleBy);

private:
    static floatvec_t getFixedRatioData(const DenseTimeValueModel &source,
                                        int channel,
                                        sv_frame_t sourceStartFrame,
                                        sv_frame_t sourceFrameCount);
    
    static int m_filterRatio;
    static floatvec_t m_filter;
};

#endif