Chris@1536: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
Chris@1536: 
Chris@1536: /*
Chris@1536:     Sonic Visualiser
Chris@1536:     An audio file viewer and annotation editor.
Chris@1536:     Centre for Digital Music, Queen Mary, University of London.
Chris@1536:    
Chris@1536:     This program is free software; you can redistribute it and/or
Chris@1536:     modify it under the terms of the GNU General Public License as
Chris@1536:     published by the Free Software Foundation; either version 2 of the
Chris@1536:     License, or (at your option) any later version.  See the file
Chris@1536:     COPYING included with this distribution for more information.
Chris@1536: */
Chris@1536: 
Chris@1536: #ifndef SV_WAVEFORM_OVERSAMPLER_H
Chris@1536: #define SV_WAVEFORM_OVERSAMPLER_H
Chris@1536: 
Chris@1536: #include "base/BaseTypes.h"
Chris@1536: 
Chris@1536: class DenseTimeValueModel;
Chris@1536: 
Chris@1536: /** Oversample the sample data from a DenseTimeValueModel by an
Chris@1536:  *  integer factor, on the assumption that the model represents
Chris@1536:  *  audio. Oversampling is carried out using a windowed sinc filter
Chris@1536:  *  for a fixed 8x ratio with further linear interpolation to handle
Chris@1536:  *  other ratios. The aim is not to provide the "best-sounding"
Chris@1536:  *  interpolation, but to provide accurate and predictable projections
Chris@1536:  *  of the theoretical waveform shape for display rendering without
Chris@1536:  *  leaving decisions about interpolation up to a resampler library.
Chris@1536:  */
Chris@1536: class WaveformOversampler
Chris@1536: {
Chris@1536: public:
Chris@1536:     /** Return an oversampled version of the audio data from the given
Chris@1536:      *  source sample range. Will query sufficient source audio before
Chris@1536:      *  and after the requested range (where available) to ensure an
Chris@1536:      *  accurate-looking result after filtering. The returned vector
Chris@1536:      *  will have sourceFrameCount * oversampleBy samples, except when
Chris@1536:      *  truncated because the end of the model was reached.
Chris@1536:      */
Chris@1745:     static floatvec_t getOversampledData(const DenseTimeValueModel &source,
Chris@1536:                                          int channel,
Chris@1536:                                          sv_frame_t sourceStartFrame,
Chris@1536:                                          sv_frame_t sourceFrameCount,
Chris@1536:                                          int oversampleBy);
Chris@1536: 
Chris@1536: private:
Chris@1745:     static floatvec_t getFixedRatioData(const DenseTimeValueModel &source,
Chris@1536:                                         int channel,
Chris@1536:                                         sv_frame_t sourceStartFrame,
Chris@1536:                                         sv_frame_t sourceFrameCount);
Chris@1536:     
Chris@1536:     static int m_filterRatio;
Chris@1536:     static floatvec_t m_filter;
Chris@1536: };
Chris@1536: 
Chris@1536: #endif