1 /* 2 * Copyright (C) 2011 Google Inc. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. Neither the name of Apple Computer, Inc. ("Apple") nor the names of 14 * its contributors may be used to endorse or promote products derived 15 * from this software without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY 18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY 21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND 24 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 #ifndef SincResampler_h 30 #define SincResampler_h 31 32 #include "AudioArray.h" 33 34 namespace WebCore { 35 36 // SincResampler is a high-quality sample-rate converter. 37 38 class SincResampler { 39 public: 40 // scaleFactor == sourceSampleRate / destinationSampleRate 41 // kernelSize can be adjusted for quality (higher is better) 42 // numberOfKernelOffsets is used for interpolation and is the number of sub-sample kernel shifts. 43 SincResampler(double scaleFactor, unsigned kernelSize = 32, unsigned numberOfKernelOffsets = 32); 44 45 // Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination. 46 void process(float* source, float* destination, unsigned numberOfSourceFrames); 47 48 // FIXME: we can add a process() method which takes an input source callback function for streaming applications 49 // where the entire input buffer is not all available. 50 51 protected: 52 void initializeKernel(); 53 void consumeSource(float* buffer, unsigned numberOfSourceFrames); 54 55 double m_scaleFactor; 56 unsigned m_kernelSize; 57 unsigned m_numberOfKernelOffsets; 58 59 // m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of size m_kernelSize. 60 // The kernel offsets are sub-sample shifts of a windowed sinc() shifted from 0.0 to 1.0 sample. 61 AudioFloatArray m_kernelStorage; 62 63 // m_virtualSourceIndex is an index on the source input buffer with sub-sample precision. 64 // It must be double precision to avoid drift. 65 double m_virtualSourceIndex; 66 67 // This is the number of destination frames we generate per processing pass on the buffer. 68 unsigned m_blockSize; 69 70 // Source is copied into this buffer for each processing pass. 71 AudioFloatArray m_inputBuffer; 72 73 float* m_source; 74 unsigned m_sourceFramesAvailable; 75 }; 76 77 } // namespace WebCore 78 79 #endif // SincResampler_h 80
