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 "EqualPowerPanner.h"
30
31#include "AudioBus.h"
32#include "AudioUtilities.h"
33#include <wtf/MathExtras.h>
34
35// Use a 50ms smoothing / de-zippering time-constant.
36const double SmoothingTimeConstant = 0.050;
37
38namespace WebCore {
39
40EqualPowerPanner::EqualPowerPanner(double sampleRate)
41    : Panner(PanningModelEqualPower)
42    , m_isFirstRender(true)
43    , m_gainL(0.0)
44    , m_gainR(0.0)
45{
46    m_smoothingConstant = AudioUtilities::discreteTimeConstantForSampleRate(SmoothingTimeConstant, sampleRate);
47}
48
49void EqualPowerPanner::pan(double azimuth, double /*elevation*/, AudioBus* inputBus, AudioBus* outputBus, size_t framesToProcess)
50{
51    // FIXME: implement stereo sources
52    bool isInputSafe = inputBus && inputBus->numberOfChannels() == 1 && framesToProcess <= inputBus->length();
53    ASSERT(isInputSafe);
54    if (!isInputSafe)
55        return;
56
57    bool isOutputSafe = outputBus && outputBus->numberOfChannels() == 2 && framesToProcess <= outputBus->length();
58    ASSERT(isOutputSafe);
59    if (!isOutputSafe)
60        return;
61
62    AudioChannel* channel = inputBus->channel(0);
63    float* sourceP = channel->data();
64    float* destinationL = outputBus->channelByType(AudioBus::ChannelLeft)->data();
65    float* destinationR = outputBus->channelByType(AudioBus::ChannelRight)->data();
66
67    if (!sourceP || !destinationL || !destinationR)
68        return;
69
70    // Pan smoothly from left to right with azimuth going from -30 -> +30 degrees.
71    double desiredPanPosition;
72    if (azimuth > 30.0)
73        desiredPanPosition = 1.0;
74    else if (azimuth < -30.0)
75        desiredPanPosition = 0.0;
76    else
77        desiredPanPosition = (azimuth + 30.0) / 60.0;
78
79    double desiredGainL = 0.5 * cos(piDouble * desiredPanPosition) + 0.5;
80    double desiredGainR = sqrt(1.0 - desiredGainL*desiredGainL);
81
82    // Don't de-zipper on first render call.
83    if (m_isFirstRender) {
84        m_isFirstRender = false;
85        m_gainL = desiredGainL;
86        m_gainR = desiredGainR;
87    }
88
89    // Cache in local variables.
90    double gainL = m_gainL;
91    double gainR = m_gainR;
92
93    // Get local copy of smoothing constant.
94    const double SmoothingConstant = m_smoothingConstant;
95
96    int n = framesToProcess;
97
98    while (n--) {
99        float input = *sourceP++;
100        gainL += (desiredGainL - gainL) * SmoothingConstant;
101        gainR += (desiredGainR - gainR) * SmoothingConstant;
102        *destinationL++ = static_cast<float>(input * gainL);
103        *destinationR++ = static_cast<float>(input * gainR);
104    }
105
106    m_gainL = gainL;
107    m_gainR = gainR;
108}
109
110} // namespace WebCore
111
112#endif // ENABLE(WEB_AUDIO)
113