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/resampler/push_sinc_resampler.h"
12 
13 #include <cstring>
14 
15 #include "webrtc/base/checks.h"
16 #include "webrtc/common_audio/include/audio_util.h"
17 
18 namespace webrtc {
19 
PushSincResampler(size_t source_frames,size_t destination_frames)20 PushSincResampler::PushSincResampler(size_t source_frames,
21                                      size_t destination_frames)
22     : resampler_(new SincResampler(source_frames * 1.0 / destination_frames,
23                                    source_frames,
24                                    this)),
25       source_ptr_(nullptr),
26       source_ptr_int_(nullptr),
27       destination_frames_(destination_frames),
28       first_pass_(true),
29       source_available_(0) {}
30 
~PushSincResampler()31 PushSincResampler::~PushSincResampler() {
32 }
33 
Resample(const int16_t * source,size_t source_length,int16_t * destination,size_t destination_capacity)34 size_t PushSincResampler::Resample(const int16_t* source,
35                                    size_t source_length,
36                                    int16_t* destination,
37                                    size_t destination_capacity) {
38   if (!float_buffer_.get())
39     float_buffer_.reset(new float[destination_frames_]);
40 
41   source_ptr_int_ = source;
42   // Pass nullptr as the float source to have Run() read from the int16 source.
43   Resample(nullptr, source_length, float_buffer_.get(), destination_frames_);
44   FloatS16ToS16(float_buffer_.get(), destination_frames_, destination);
45   source_ptr_int_ = nullptr;
46   return destination_frames_;
47 }
48 
Resample(const float * source,size_t source_length,float * destination,size_t destination_capacity)49 size_t PushSincResampler::Resample(const float* source,
50                                    size_t source_length,
51                                    float* destination,
52                                    size_t destination_capacity) {
53   RTC_CHECK_EQ(source_length, resampler_->request_frames());
54   RTC_CHECK_GE(destination_capacity, destination_frames_);
55   // Cache the source pointer. Calling Resample() will immediately trigger
56   // the Run() callback whereupon we provide the cached value.
57   source_ptr_ = source;
58   source_available_ = source_length;
59 
60   // On the first pass, we call Resample() twice. During the first call, we
61   // provide dummy input and discard the output. This is done to prime the
62   // SincResampler buffer with the correct delay (half the kernel size), thereby
63   // ensuring that all later Resample() calls will only result in one input
64   // request through Run().
65   //
66   // If this wasn't done, SincResampler would call Run() twice on the first
67   // pass, and we'd have to introduce an entire |source_frames| of delay, rather
68   // than the minimum half kernel.
69   //
70   // It works out that ChunkSize() is exactly the amount of output we need to
71   // request in order to prime the buffer with a single Run() request for
72   // |source_frames|.
73   if (first_pass_)
74     resampler_->Resample(resampler_->ChunkSize(), destination);
75 
76   resampler_->Resample(destination_frames_, destination);
77   source_ptr_ = nullptr;
78   return destination_frames_;
79 }
80 
Run(size_t frames,float * destination)81 void PushSincResampler::Run(size_t frames, float* destination) {
82   // Ensure we are only asked for the available samples. This would fail if
83   // Run() was triggered more than once per Resample() call.
84   RTC_CHECK_EQ(source_available_, frames);
85 
86   if (first_pass_) {
87     // Provide dummy input on the first pass, the output of which will be
88     // discarded, as described in Resample().
89     std::memset(destination, 0, frames * sizeof(*destination));
90     first_pass_ = false;
91     return;
92   }
93 
94   if (source_ptr_) {
95     std::memcpy(destination, source_ptr_, frames * sizeof(*destination));
96   } else {
97     for (size_t i = 0; i < frames; ++i)
98       destination[i] = static_cast<float>(source_ptr_int_[i]);
99   }
100   source_available_ -= frames;
101 }
102 
103 }  // namespace webrtc
104