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 "platform/audio/EqualPowerPanner.h"
30
31#include <algorithm>
32#include "platform/audio/AudioBus.h"
33#include "platform/audio/AudioUtilities.h"
34#include "wtf/MathExtras.h"
35
36// Use a 50ms smoothing / de-zippering time-constant.
37const float SmoothingTimeConstant = 0.050f;
38
39namespace blink {
40
41EqualPowerPanner::EqualPowerPanner(float sampleRate)
42    : Panner(PanningModelEqualPower)
43    , m_isFirstRender(true)
44    , m_gainL(0.0)
45    , m_gainR(0.0)
46{
47    m_smoothingConstant = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate);
48}
49
50void EqualPowerPanner::pan(double azimuth, double /*elevation*/, const AudioBus* inputBus, AudioBus* outputBus, size_t framesToProcess)
51{
52    bool isInputSafe = inputBus && (inputBus->numberOfChannels() == 1 || inputBus->numberOfChannels() == 2) && framesToProcess <= inputBus->length();
53    ASSERT(isInputSafe);
54    if (!isInputSafe)
55        return;
56
57    unsigned numberOfInputChannels = inputBus->numberOfChannels();
58
59    bool isOutputSafe = outputBus && outputBus->numberOfChannels() == 2 && framesToProcess <= outputBus->length();
60    ASSERT(isOutputSafe);
61    if (!isOutputSafe)
62        return;
63
64    const float* sourceL = inputBus->channel(0)->data();
65    const float* sourceR = numberOfInputChannels > 1 ? inputBus->channel(1)->data() : sourceL;
66    float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->mutableData();
67    float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->mutableData();
68
69    if (!sourceL || !sourceR || !destinationL || !destinationR)
70        return;
71
72    // Clamp azimuth to allowed range of -180 -> +180.
73    azimuth = std::max(-180.0, azimuth);
74    azimuth = std::min(180.0, azimuth);
75
76    // Alias the azimuth ranges behind us to in front of us:
77    // -90 -> -180 to -90 -> 0 and 90 -> 180 to 90 -> 0
78    if (azimuth < -90)
79        azimuth = -180 - azimuth;
80    else if (azimuth > 90)
81        azimuth = 180 - azimuth;
82
83    double desiredPanPosition;
84    double desiredGainL;
85    double desiredGainR;
86
87    if (numberOfInputChannels == 1) { // For mono source case.
88        // Pan smoothly from left to right with azimuth going from -90 -> +90 degrees.
89        desiredPanPosition = (azimuth + 90) / 180;
90    } else { // For stereo source case.
91        if (azimuth <= 0) { // from -90 -> 0
92            // sourceL -> destL and "equal-power pan" sourceR as in mono case
93            // by transforming the "azimuth" value from -90 -> 0 degrees into the range -90 -> +90.
94            desiredPanPosition = (azimuth + 90) / 90;
95        } else { // from 0 -> +90
96            // sourceR -> destR and "equal-power pan" sourceL as in mono case
97            // by transforming the "azimuth" value from 0 -> +90 degrees into the range -90 -> +90.
98            desiredPanPosition = azimuth / 90;
99        }
100    }
101
102    desiredGainL = std::cos(piOverTwoDouble * desiredPanPosition);
103    desiredGainR = std::sin(piOverTwoDouble * desiredPanPosition);
104
105    // Don't de-zipper on first render call.
106    if (m_isFirstRender) {
107        m_isFirstRender = false;
108        m_gainL = desiredGainL;
109        m_gainR = desiredGainR;
110    }
111
112    // Cache in local variables.
113    double gainL = m_gainL;
114    double gainR = m_gainR;
115
116    // Get local copy of smoothing constant.
117    const double SmoothingConstant = m_smoothingConstant;
118
119    int n = framesToProcess;
120
121    if (numberOfInputChannels == 1) { // For mono source case.
122        while (n--) {
123            float inputL = *sourceL++;
124            gainL += (desiredGainL - gainL) * SmoothingConstant;
125            gainR += (desiredGainR - gainR) * SmoothingConstant;
126            *destinationL++ = static_cast<float>(inputL * gainL);
127            *destinationR++ = static_cast<float>(inputL * gainR);
128        }
129    } else { // For stereo source case.
130        if (azimuth <= 0) { // from -90 -> 0
131            while (n--) {
132                float inputL = *sourceL++;
133                float inputR = *sourceR++;
134                gainL += (desiredGainL - gainL) * SmoothingConstant;
135                gainR += (desiredGainR - gainR) * SmoothingConstant;
136                *destinationL++ = static_cast<float>(inputL + inputR * gainL);
137                *destinationR++ = static_cast<float>(inputR * gainR);
138            }
139        } else { // from 0 -> +90
140            while (n--) {
141                float inputL = *sourceL++;
142                float inputR = *sourceR++;
143                gainL += (desiredGainL - gainL) * SmoothingConstant;
144                gainR += (desiredGainR - gainR) * SmoothingConstant;
145                *destinationL++ = static_cast<float>(inputL * gainL);
146                *destinationR++ = static_cast<float>(inputR + inputL * gainR);
147            }
148        }
149    }
150
151    m_gainL = gainL;
152    m_gainR = gainR;
153}
154
155} // namespace blink
156
157#endif // ENABLE(WEB_AUDIO)
158