diff data/model/WaveformOversampler.h @ 1536:eb10ed56d5a4 zoom

Add custom waveform oversampler method

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/data/model/WaveformOversampler.h	Wed Sep 26 13:03:46 2018 +0100
@@ -0,0 +1,57 @@
+/* -*- 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