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.
36 const double SmoothingTimeConstant = 0.050;
37
38 namespace WebCore {
39
EqualPowerPanner(double sampleRate)40 EqualPowerPanner::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
pan(double azimuth,double,AudioBus * inputBus,AudioBus * outputBus,size_t framesToProcess)49 void 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