2 * Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
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.
11 #include "webrtc/common_audio/include/audio_util.h"
16 #include "webrtc/common_audio/resampler/push_sinc_resampler.h"
20 PushSincResampler::PushSincResampler(int source_frames, int destination_frames)
21 : resampler_(new SincResampler(source_frames * 1.0 / destination_frames,
25 source_ptr_int_(NULL),
26 destination_frames_(destination_frames),
28 source_available_(0) {}
30 PushSincResampler::~PushSincResampler() {
33 int PushSincResampler::Resample(const int16_t* source,
36 int destination_capacity) {
37 if (!float_buffer_.get())
38 float_buffer_.reset(new float[destination_frames_]);
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 FloatS16ToS16(float_buffer_.get(), destination_frames_, destination);
44 source_ptr_int_ = NULL;
45 return destination_frames_;
48 int PushSincResampler::Resample(const float* source,
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.
57 source_available_ = source_length;
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().
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.
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
73 resampler_->Resample(resampler_->ChunkSize(), destination);
75 resampler_->Resample(destination_frames_, destination);
77 return destination_frames_;
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);
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));
94 memcpy(destination, source_ptr_, frames * sizeof(float));
96 for (int i = 0; i < frames; ++i)
97 destination[i] = static_cast<float>(source_ptr_int_[i]);
99 source_available_ -= frames;
102 } // namespace webrtc