1 /* 2 * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 #include "webrtc/common_audio/include/audio_util.h" 12 13 #include <assert.h> 14 #include <string.h> 15 16 #include "webrtc/common_audio/resampler/push_sinc_resampler.h" 17 18 namespace webrtc { 19 20 PushSincResampler::PushSincResampler(int source_frames, int destination_frames) 21 : resampler_(new SincResampler(source_frames * 1.0 / destination_frames, 22 source_frames, 23 this)), 24 source_ptr_(NULL), 25 source_ptr_int_(NULL), 26 destination_frames_(destination_frames), 27 first_pass_(true), 28 source_available_(0) {} 29 30 PushSincResampler::~PushSincResampler() { 31 } 32 33 int PushSincResampler::Resample(const int16_t* source, 34 int source_length, 35 int16_t* destination, 36 int destination_capacity) { 37 if (!float_buffer_.get()) 38 float_buffer_.reset(new float[destination_frames_]); 39 40 source_ptr_int_ = source; 41 // Pass NULL as the float source to have Run() read from the int16 source. 42 Resample(NULL, source_length, float_buffer_.get(), destination_frames_); 43 RoundToInt16(float_buffer_.get(), destination_frames_, destination); 44 source_ptr_int_ = NULL; 45 return destination_frames_; 46 } 47 48 int PushSincResampler::Resample(const float* source, 49 int source_length, 50 float* destination, 51 int destination_capacity) { 52 assert(source_length == resampler_->request_frames()); 53 assert(destination_capacity >= destination_frames_); 54 // Cache the source pointer. Calling Resample() will immediately trigger 55 // the Run() callback whereupon we provide the cached value. 56 source_ptr_ = source; 57 source_available_ = source_length; 58 59 // On the first pass, we call Resample() twice. During the first call, we 60 // provide dummy input and discard the output. This is done to prime the 61 // SincResampler buffer with the correct delay (half the kernel size), thereby 62 // ensuring that all later Resample() calls will only result in one input 63 // request through Run(). 64 // 65 // If this wasn't done, SincResampler would call Run() twice on the first 66 // pass, and we'd have to introduce an entire |source_frames| of delay, rather 67 // than the minimum half kernel. 68 // 69 // It works out that ChunkSize() is exactly the amount of output we need to 70 // request in order to prime the buffer with a single Run() request for 71 // |source_frames|. 72 if (first_pass_) 73 resampler_->Resample(resampler_->ChunkSize(), destination); 74 75 resampler_->Resample(destination_frames_, destination); 76 source_ptr_ = NULL; 77 return destination_frames_; 78 } 79 80 void PushSincResampler::Run(int frames, float* destination) { 81 // Ensure we are only asked for the available samples. This would fail if 82 // Run() was triggered more than once per Resample() call. 83 assert(source_available_ == frames); 84 85 if (first_pass_) { 86 // Provide dummy input on the first pass, the output of which will be 87 // discarded, as described in Resample(). 88 memset(destination, 0, frames * sizeof(float)); 89 first_pass_ = false; 90 return; 91 } 92 93 if (source_ptr_) { 94 memcpy(destination, source_ptr_, frames * sizeof(float)); 95 } else { 96 for (int i = 0; i < frames; ++i) 97 destination[i] = static_cast<float>(source_ptr_int_[i]); 98 } 99 source_available_ -= frames; 100 } 101 102 } // namespace webrtc 103
