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
PushSincResampler(int source_frames,int destination_frames)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
~PushSincResampler()30 PushSincResampler::~PushSincResampler() {
31 }
32
Resample(const int16_t * source,int source_length,int16_t * destination,int destination_capacity)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
Resample(const float * source,int source_length,float * destination,int destination_capacity)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
Run(int frames,float * destination)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