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 "core/platform/audio/AudioArray.h" 33 #include "core/platform/audio/AudioSourceProvider.h" 34 35 namespace WebCore { 36 37 // SincResampler is a high-quality sample-rate converter. 38 39 class SincResampler { 40 public: 41 // scaleFactor == sourceSampleRate / destinationSampleRate 42 // kernelSize can be adjusted for quality (higher is better) 43 // numberOfKernelOffsets is used for interpolation and is the number of sub-sample kernel shifts. 44 SincResampler(double scaleFactor, unsigned kernelSize = 32, unsigned numberOfKernelOffsets = 32); 45 46 // Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination. 47 void process(const float* source, float* destination, unsigned numberOfSourceFrames); 48 49 // Process with input source callback function for streaming applications. 50 void process(AudioSourceProvider*, float* destination, size_t framesToProcess); 51 52 protected: 53 void initializeKernel(); 54 void consumeSource(float* buffer, unsigned numberOfSourceFrames); 55 56 double m_scaleFactor; 57 unsigned m_kernelSize; 58 unsigned m_numberOfKernelOffsets; 59 60 // m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of size m_kernelSize. 61 // The kernel offsets are sub-sample shifts of a windowed sinc() shifted from 0.0 to 1.0 sample. 62 AudioFloatArray m_kernelStorage; 63 64 // m_virtualSourceIndex is an index on the source input buffer with sub-sample precision. 65 // It must be double precision to avoid drift. 66 double m_virtualSourceIndex; 67 68 // This is the number of destination frames we generate per processing pass on the buffer. 69 unsigned m_blockSize; 70 71 // Source is copied into this buffer for each processing pass. 72 AudioFloatArray m_inputBuffer; 73 74 const float* m_source; 75 unsigned m_sourceFramesAvailable; 76 77 // m_sourceProvider is used to provide the audio input stream to the resampler. 78 AudioSourceProvider* m_sourceProvider; 79 80 // The buffer is primed once at the very beginning of processing. 81 bool m_isBufferPrimed; 82 }; 83 84 } // namespace WebCore 85 86 #endif // SincResampler_h 87
