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 *
8 * 1.  Redistributions of source code must retain the above copyright
9 *     notice, this list of conditions and the following disclaimer.
10 * 2.  Redistributions in binary form must reproduce the above copyright
11 *     notice, this list of conditions and the following disclaimer in the
12 *     documentation and/or other materials provided with the distribution.
13 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
14 *     its contributors may be used to endorse or promote products derived
15 *     from this software without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
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20 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
21 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
22 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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26 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27 */
28
29#include "config.h"
30
31#if ENABLE(WEB_AUDIO)
32
33#include "platform/audio/ReverbConvolver.h"
34
35#include "platform/Task.h"
36#include "platform/audio/AudioBus.h"
37#include "platform/audio/VectorMath.h"
38#include "public/platform/Platform.h"
39#include "public/platform/WebThread.h"
40
41namespace blink {
42
43using namespace VectorMath;
44
45const int InputBufferSize = 8 * 16384;
46
47// We only process the leading portion of the impulse response in the real-time thread.  We don't exceed this length.
48// It turns out then, that the background thread has about 278msec of scheduling slop.
49// Empirically, this has been found to be a good compromise between giving enough time for scheduling slop,
50// while still minimizing the amount of processing done in the primary (high-priority) thread.
51// This was found to be a good value on Mac OS X, and may work well on other platforms as well, assuming
52// the very rough scheduling latencies are similar on these time-scales.  Of course, this code may need to be
53// tuned for individual platforms if this assumption is found to be incorrect.
54const size_t RealtimeFrameLimit = 8192  + 4096; // ~278msec @ 44.1KHz
55
56const size_t MinFFTSize = 128;
57const size_t MaxRealtimeFFTSize = 2048;
58
59ReverbConvolver::ReverbConvolver(AudioChannel* impulseResponse, size_t renderSliceSize, size_t maxFFTSize, size_t convolverRenderPhase, bool useBackgroundThreads)
60    : m_impulseResponseLength(impulseResponse->length())
61    , m_accumulationBuffer(impulseResponse->length() + renderSliceSize)
62    , m_inputBuffer(InputBufferSize)
63    , m_minFFTSize(MinFFTSize) // First stage will have this size - successive stages will double in size each time
64    , m_maxFFTSize(maxFFTSize) // until we hit m_maxFFTSize
65{
66    // If we are using background threads then don't exceed this FFT size for the
67    // stages which run in the real-time thread.  This avoids having only one or two
68    // large stages (size 16384 or so) at the end which take a lot of time every several
69    // processing slices.  This way we amortize the cost over more processing slices.
70    m_maxRealtimeFFTSize = MaxRealtimeFFTSize;
71
72    // For the moment, a good way to know if we have real-time constraint is to check if we're using background threads.
73    // Otherwise, assume we're being run from a command-line tool.
74    bool hasRealtimeConstraint = useBackgroundThreads;
75
76    const float* response = impulseResponse->data();
77    size_t totalResponseLength = impulseResponse->length();
78
79    // The total latency is zero because the direct-convolution is used in the leading portion.
80    size_t reverbTotalLatency = 0;
81
82    size_t stageOffset = 0;
83    int i = 0;
84    size_t fftSize = m_minFFTSize;
85    while (stageOffset < totalResponseLength) {
86        size_t stageSize = fftSize / 2;
87
88        // For the last stage, it's possible that stageOffset is such that we're straddling the end
89        // of the impulse response buffer (if we use stageSize), so reduce the last stage's length...
90        if (stageSize + stageOffset > totalResponseLength)
91            stageSize = totalResponseLength - stageOffset;
92
93        // This "staggers" the time when each FFT happens so they don't all happen at the same time
94        int renderPhase = convolverRenderPhase + i * renderSliceSize;
95
96        bool useDirectConvolver = !stageOffset;
97
98        OwnPtr<ReverbConvolverStage> stage = adoptPtr(new ReverbConvolverStage(response, totalResponseLength, reverbTotalLatency, stageOffset, stageSize, fftSize, renderPhase, renderSliceSize, &m_accumulationBuffer, useDirectConvolver));
99
100        bool isBackgroundStage = false;
101
102        if (useBackgroundThreads && stageOffset > RealtimeFrameLimit) {
103            m_backgroundStages.append(stage.release());
104            isBackgroundStage = true;
105        } else
106            m_stages.append(stage.release());
107
108        stageOffset += stageSize;
109        ++i;
110
111        if (!useDirectConvolver) {
112            // Figure out next FFT size
113            fftSize *= 2;
114        }
115
116        if (hasRealtimeConstraint && !isBackgroundStage && fftSize > m_maxRealtimeFFTSize)
117            fftSize = m_maxRealtimeFFTSize;
118        if (fftSize > m_maxFFTSize)
119            fftSize = m_maxFFTSize;
120    }
121
122    // Start up background thread
123    // FIXME: would be better to up the thread priority here.  It doesn't need to be real-time, but higher than the default...
124    if (useBackgroundThreads && m_backgroundStages.size() > 0)
125        m_backgroundThread = adoptPtr(Platform::current()->createThread("Reverb convolution background thread"));
126}
127
128ReverbConvolver::~ReverbConvolver()
129{
130    // Wait for background thread to stop
131    m_backgroundThread.clear();
132}
133
134void ReverbConvolver::processInBackground()
135{
136    // Process all of the stages until their read indices reach the input buffer's write index
137    int writeIndex = m_inputBuffer.writeIndex();
138
139    // Even though it doesn't seem like every stage needs to maintain its own version of readIndex
140    // we do this in case we want to run in more than one background thread.
141    int readIndex;
142
143    while ((readIndex = m_backgroundStages[0]->inputReadIndex()) != writeIndex) { // FIXME: do better to detect buffer overrun...
144        // The ReverbConvolverStages need to process in amounts which evenly divide half the FFT size
145        const int SliceSize = MinFFTSize / 2;
146
147        // Accumulate contributions from each stage
148        for (size_t i = 0; i < m_backgroundStages.size(); ++i)
149            m_backgroundStages[i]->processInBackground(this, SliceSize);
150    }
151}
152
153void ReverbConvolver::process(const AudioChannel* sourceChannel, AudioChannel* destinationChannel, size_t framesToProcess)
154{
155    bool isSafe = sourceChannel && destinationChannel && sourceChannel->length() >= framesToProcess && destinationChannel->length() >= framesToProcess;
156    ASSERT(isSafe);
157    if (!isSafe)
158        return;
159
160    const float* source = sourceChannel->data();
161    float* destination = destinationChannel->mutableData();
162    bool isDataSafe = source && destination;
163    ASSERT(isDataSafe);
164    if (!isDataSafe)
165        return;
166
167    // Feed input buffer (read by all threads)
168    m_inputBuffer.write(source, framesToProcess);
169
170    // Accumulate contributions from each stage
171    for (size_t i = 0; i < m_stages.size(); ++i)
172        m_stages[i]->process(source, framesToProcess);
173
174    // Finally read from accumulation buffer
175    m_accumulationBuffer.readAndClear(destination, framesToProcess);
176
177    // Now that we've buffered more input, post another task to the background thread.
178    if (m_backgroundThread)
179        m_backgroundThread->postTask(new Task(WTF::bind(&ReverbConvolver::processInBackground, this)));
180}
181
182void ReverbConvolver::reset()
183{
184    for (size_t i = 0; i < m_stages.size(); ++i)
185        m_stages[i]->reset();
186
187    for (size_t i = 0; i < m_backgroundStages.size(); ++i)
188        m_backgroundStages[i]->reset();
189
190    m_accumulationBuffer.reset();
191    m_inputBuffer.reset();
192}
193
194size_t ReverbConvolver::latencyFrames() const
195{
196    return 0;
197}
198
199} // namespace blink
200
201#endif // ENABLE(WEB_AUDIO)
202