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 #include "config.h"
26
27 #if ENABLE(WEB_AUDIO)
28
29 #include "DelayDSPKernel.h"
30
31 #include "AudioUtilities.h"
32 #include <algorithm>
33
34 using namespace std;
35
36 const double DefaultMaxDelayTime = 1.0;
37 const double SmoothingTimeConstant = 0.020; // 20ms
38
39 namespace WebCore {
40
DelayDSPKernel(DelayProcessor * processor)41 DelayDSPKernel::DelayDSPKernel(DelayProcessor* processor)
42 : AudioDSPKernel(processor)
43 , m_maxDelayTime(DefaultMaxDelayTime)
44 , m_writeIndex(0)
45 , m_firstTime(true)
46 {
47 ASSERT(processor && processor->sampleRate() > 0);
48 if (!processor)
49 return;
50
51 m_buffer.resize(static_cast<size_t>(processor->sampleRate() * DefaultMaxDelayTime));
52 m_buffer.zero();
53
54 m_smoothingRate = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, processor->sampleRate());
55 }
56
DelayDSPKernel(double maxDelayTime,double sampleRate)57 DelayDSPKernel::DelayDSPKernel(double maxDelayTime, double sampleRate)
58 : AudioDSPKernel(sampleRate)
59 , m_maxDelayTime(maxDelayTime)
60 , m_writeIndex(0)
61 , m_firstTime(true)
62 {
63 ASSERT(maxDelayTime > 0.0);
64 if (maxDelayTime <= 0.0)
65 return;
66
67 size_t bufferLength = static_cast<size_t>(sampleRate * maxDelayTime);
68 ASSERT(bufferLength);
69 if (!bufferLength)
70 return;
71
72 m_buffer.resize(bufferLength);
73 m_buffer.zero();
74
75 m_smoothingRate = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate);
76 }
77
process(const float * source,float * destination,size_t framesToProcess)78 void DelayDSPKernel::process(const float* source, float* destination, size_t framesToProcess)
79 {
80 size_t bufferLength = m_buffer.size();
81 float* buffer = m_buffer.data();
82
83 ASSERT(bufferLength);
84 if (!bufferLength)
85 return;
86
87 ASSERT(source && destination);
88 if (!source || !destination)
89 return;
90
91 double sampleRate = this->sampleRate();
92 double delayTime = delayProcessor() ? delayProcessor()->delayTime()->value() : m_desiredDelayFrames / sampleRate;
93
94 // Make sure the delay time is in a valid range.
95 delayTime = min(maxDelayTime(), delayTime);
96 delayTime = max(0.0, delayTime);
97
98 if (m_firstTime) {
99 m_currentDelayTime = delayTime;
100 m_firstTime = false;
101 }
102
103 int n = framesToProcess;
104 while (n--) {
105 // Approach desired delay time.
106 m_currentDelayTime += (delayTime - m_currentDelayTime) * m_smoothingRate;
107
108 double desiredDelayFrames = m_currentDelayTime * sampleRate;
109
110 double readPosition = m_writeIndex + bufferLength - desiredDelayFrames;
111 if (readPosition > bufferLength)
112 readPosition -= bufferLength;
113
114 // Linearly interpolate in-between delay times.
115 int readIndex1 = static_cast<int>(readPosition);
116 int readIndex2 = (readIndex1 + 1) % bufferLength;
117 double interpolationFactor = readPosition - readIndex1;
118
119 double input = static_cast<float>(*source++);
120 buffer[m_writeIndex] = static_cast<float>(input);
121 m_writeIndex = (m_writeIndex + 1) % bufferLength;
122
123 double sample1 = buffer[readIndex1];
124 double sample2 = buffer[readIndex2];
125
126 double output = (1.0 - interpolationFactor) * sample1 + interpolationFactor * sample2;
127
128 *destination++ = static_cast<float>(output);
129 }
130 }
131
reset()132 void DelayDSPKernel::reset()
133 {
134 m_firstTime = true;
135 m_buffer.zero();
136 }
137
138 } // namespace WebCore
139
140 #endif // ENABLE(WEB_AUDIO)
141