1 /* 2 * Copyright (C) 2010, 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 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY 14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 15 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 16 * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY 17 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 18 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 19 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON 20 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS 22 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25 #ifndef AudioResamplerKernel_h 26 #define AudioResamplerKernel_h 27 28 #include "AudioArray.h" 29 30 namespace WebCore { 31 32 class AudioResampler; 33 34 // AudioResamplerKernel does resampling on a single mono channel. 35 // It uses a simple linear interpolation for good performance. 36 37 class AudioResamplerKernel { 38 public: 39 AudioResamplerKernel(AudioResampler*); 40 41 // getSourcePointer() should be called each time before process() is called. 42 // Given a number of frames to process (for subsequent call to process()), it returns a pointer and numberOfSourceFramesNeeded 43 // where sample data should be copied. This sample data provides the input to the resampler when process() is called. 44 // framesToProcess must be less than or equal to MaxFramesToProcess. 45 float* getSourcePointer(size_t framesToProcess, size_t* numberOfSourceFramesNeeded); 46 47 // process() resamples framesToProcess frames from the source into destination. 48 // Each call to process() must be preceded by a call to getSourcePointer() so that source input may be supplied. 49 // framesToProcess must be less than or equal to MaxFramesToProcess. 50 void process(float* destination, size_t framesToProcess); 51 52 // Resets the processing state. 53 void reset(); 54 55 static const size_t MaxFramesToProcess; 56 57 private: 58 double rate() const; 59 60 AudioResampler* m_resampler; 61 AudioFloatArray m_sourceBuffer; 62 63 // This is a (floating point) read index on the input stream. 64 double m_virtualReadIndex; 65 66 // We need to have continuity from one call of process() to the next. 67 // m_lastValues stores the last two sample values from the last call to process(). 68 // m_fillIndex represents how many buffered samples we have which can be as many as 2. 69 // For the first call to process() (or after reset()) there will be no buffered samples. 70 float m_lastValues[2]; 71 unsigned m_fillIndex; 72 }; 73 74 } // namespace WebCore 75 76 #endif // AudioResamplerKernel_h 77
