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 "platform/PlatformExport.h" 33 #include "platform/audio/AudioArray.h" 34 #include "platform/audio/AudioSourceProvider.h" 35 36 namespace WebCore { 37 38 // SincResampler is a high-quality sample-rate converter. 39 40 class PLATFORM_EXPORT SincResampler { 41 public: 42 // scaleFactor == sourceSampleRate / destinationSampleRate 43 // kernelSize can be adjusted for quality (higher is better) 44 // numberOfKernelOffsets is used for interpolation and is the number of sub-sample kernel shifts. 45 SincResampler(double scaleFactor, unsigned kernelSize = 32, unsigned numberOfKernelOffsets = 32); 46 47 // Processes numberOfSourceFrames from source to produce numberOfSourceFrames / scaleFactor frames in destination. 48 void process(const float* source, float* destination, unsigned numberOfSourceFrames); 49 50 // Process with input source callback function for streaming applications. 51 void process(AudioSourceProvider*, float* destination, size_t framesToProcess); 52 53 protected: 54 void initializeKernel(); 55 void consumeSource(float* buffer, unsigned numberOfSourceFrames); 56 57 double m_scaleFactor; 58 unsigned m_kernelSize; 59 unsigned m_numberOfKernelOffsets; 60 61 // m_kernelStorage has m_numberOfKernelOffsets kernels back-to-back, each of size m_kernelSize. 62 // The kernel offsets are sub-sample shifts of a windowed sinc() shifted from 0.0 to 1.0 sample. 63 AudioFloatArray m_kernelStorage; 64 65 // m_virtualSourceIndex is an index on the source input buffer with sub-sample precision. 66 // It must be double precision to avoid drift. 67 double m_virtualSourceIndex; 68 69 // This is the number of destination frames we generate per processing pass on the buffer. 70 unsigned m_blockSize; 71 72 // Source is copied into this buffer for each processing pass. 73 AudioFloatArray m_inputBuffer; 74 75 const float* m_source; 76 unsigned m_sourceFramesAvailable; 77 78 // m_sourceProvider is used to provide the audio input stream to the resampler. 79 AudioSourceProvider* m_sourceProvider; 80 81 // The buffer is primed once at the very beginning of processing. 82 bool m_isBufferPrimed; 83 }; 84 85 } // namespace WebCore 86 87 #endif // SincResampler_h 88
