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
18 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
19 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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;
23 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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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 "ReverbConvolver.h"
34
35#include "VectorMath.h"
36#include "AudioBus.h"
37
38namespace WebCore {
39
40using namespace VectorMath;
41
42const int InputBufferSize = 8 * 16384;
43
44// We only process the leading portion of the impulse response in the real-time thread.  We don't exceed this length.
45// It turns out then, that the background thread has about 278msec of scheduling slop.
46// Empirically, this has been found to be a good compromise between giving enough time for scheduling slop,
47// while still minimizing the amount of processing done in the primary (high-priority) thread.
48// This was found to be a good value on Mac OS X, and may work well on other platforms as well, assuming
49// the very rough scheduling latencies are similar on these time-scales.  Of course, this code may need to be
50// tuned for individual platforms if this assumption is found to be incorrect.
51const size_t RealtimeFrameLimit = 8192  + 4096; // ~278msec @ 44.1KHz
52
53const size_t MinFFTSize = 256;
54const size_t MaxRealtimeFFTSize = 2048;
55
56static void* backgroundThreadEntry(void* threadData)
57{
58    ReverbConvolver* reverbConvolver = static_cast<ReverbConvolver*>(threadData);
59    reverbConvolver->backgroundThreadEntry();
60    return 0;
61}
62
63ReverbConvolver::ReverbConvolver(AudioChannel* impulseResponse, size_t renderSliceSize, size_t maxFFTSize, size_t convolverRenderPhase, bool useBackgroundThreads)
64    : m_impulseResponseLength(impulseResponse->length())
65    , m_accumulationBuffer(impulseResponse->length() + renderSliceSize)
66    , m_inputBuffer(InputBufferSize)
67    , m_renderSliceSize(renderSliceSize)
68    , m_minFFTSize(MinFFTSize) // First stage will have this size - successive stages will double in size each time
69    , m_maxFFTSize(maxFFTSize) // until we hit m_maxFFTSize
70    , m_useBackgroundThreads(useBackgroundThreads)
71    , m_backgroundThread(0)
72    , m_wantsToExit(false)
73    , m_moreInputBuffered(false)
74{
75    // If we are using background threads then don't exceed this FFT size for the
76    // stages which run in the real-time thread.  This avoids having only one or two
77    // large stages (size 16384 or so) at the end which take a lot of time every several
78    // processing slices.  This way we amortize the cost over more processing slices.
79    m_maxRealtimeFFTSize = MaxRealtimeFFTSize;
80
81    // For the moment, a good way to know if we have real-time constraint is to check if we're using background threads.
82    // Otherwise, assume we're being run from a command-line tool.
83    bool hasRealtimeConstraint = useBackgroundThreads;
84
85    float* response = impulseResponse->data();
86    size_t totalResponseLength = impulseResponse->length();
87
88    // Because we're not using direct-convolution in the leading portion, the reverb has an overall latency of half the first-stage FFT size
89    size_t reverbTotalLatency = m_minFFTSize / 2;
90
91    size_t stageOffset = 0;
92    int i = 0;
93    size_t fftSize = m_minFFTSize;
94    while (stageOffset < totalResponseLength) {
95        size_t stageSize = fftSize / 2;
96
97        // For the last stage, it's possible that stageOffset is such that we're straddling the end
98        // of the impulse response buffer (if we use stageSize), so reduce the last stage's length...
99        if (stageSize + stageOffset > totalResponseLength)
100            stageSize = totalResponseLength - stageOffset;
101
102        // This "staggers" the time when each FFT happens so they don't all happen at the same time
103        int renderPhase = convolverRenderPhase + i * renderSliceSize;
104
105        OwnPtr<ReverbConvolverStage> stage(new ReverbConvolverStage(response, totalResponseLength, reverbTotalLatency, stageOffset, stageSize, fftSize, renderPhase, renderSliceSize, &m_accumulationBuffer));
106
107        bool isBackgroundStage = false;
108
109        if (this->useBackgroundThreads() && stageOffset > RealtimeFrameLimit) {
110            m_backgroundStages.append(stage.release());
111            isBackgroundStage = true;
112        } else
113            m_stages.append(stage.release());
114
115        stageOffset += stageSize;
116        ++i;
117
118        // Figure out next FFT size
119        fftSize *= 2;
120        if (hasRealtimeConstraint && !isBackgroundStage && fftSize > m_maxRealtimeFFTSize)
121            fftSize = m_maxRealtimeFFTSize;
122        if (fftSize > m_maxFFTSize)
123            fftSize = m_maxFFTSize;
124    }
125
126    // Start up background thread
127    // FIXME: would be better to up the thread priority here.  It doesn't need to be real-time, but higher than the default...
128    if (this->useBackgroundThreads() && m_backgroundStages.size() > 0)
129        m_backgroundThread = createThread(WebCore::backgroundThreadEntry, this, "convolution background thread");
130}
131
132ReverbConvolver::~ReverbConvolver()
133{
134    // Wait for background thread to stop
135    if (useBackgroundThreads() && m_backgroundThread) {
136        m_wantsToExit = true;
137
138        // Wake up thread so it can return
139        {
140            MutexLocker locker(m_backgroundThreadLock);
141            m_moreInputBuffered = true;
142            m_backgroundThreadCondition.signal();
143        }
144
145        waitForThreadCompletion(m_backgroundThread, 0);
146    }
147}
148
149void ReverbConvolver::backgroundThreadEntry()
150{
151    while (!m_wantsToExit) {
152        // Wait for realtime thread to give us more input
153        m_moreInputBuffered = false;
154        {
155            MutexLocker locker(m_backgroundThreadLock);
156            while (!m_moreInputBuffered && !m_wantsToExit)
157                m_backgroundThreadCondition.wait(m_backgroundThreadLock);
158        }
159
160        // Process all of the stages until their read indices reach the input buffer's write index
161        int writeIndex = m_inputBuffer.writeIndex();
162
163        // Even though it doesn't seem like every stage needs to maintain its own version of readIndex
164        // we do this in case we want to run in more than one background thread.
165        int readIndex;
166
167        while ((readIndex = m_backgroundStages[0]->inputReadIndex()) != writeIndex) { // FIXME: do better to detect buffer overrun...
168            // The ReverbConvolverStages need to process in amounts which evenly divide half the FFT size
169            const int SliceSize = MinFFTSize / 2;
170
171            // Accumulate contributions from each stage
172            for (size_t i = 0; i < m_backgroundStages.size(); ++i)
173                m_backgroundStages[i]->processInBackground(this, SliceSize);
174        }
175    }
176}
177
178void ReverbConvolver::process(AudioChannel* sourceChannel, AudioChannel* destinationChannel, size_t framesToProcess)
179{
180    bool isSafe = sourceChannel && destinationChannel && sourceChannel->length() >= framesToProcess && destinationChannel->length() >= framesToProcess;
181    ASSERT(isSafe);
182    if (!isSafe)
183        return;
184
185    float* source = sourceChannel->data();
186    float* destination = destinationChannel->data();
187    bool isDataSafe = source && destination;
188    ASSERT(isDataSafe);
189    if (!isDataSafe)
190        return;
191
192    // Feed input buffer (read by all threads)
193    m_inputBuffer.write(source, framesToProcess);
194
195    // Accumulate contributions from each stage
196    for (size_t i = 0; i < m_stages.size(); ++i)
197        m_stages[i]->process(source, framesToProcess);
198
199    // Finally read from accumulation buffer
200    m_accumulationBuffer.readAndClear(destination, framesToProcess);
201
202    // Now that we've buffered more input, wake up our background thread.
203
204    // Not using a MutexLocker looks strange, but we use a tryLock() instead because this is run on the real-time
205    // thread where it is a disaster for the lock to be contended (causes audio glitching).  It's OK if we fail to
206    // signal from time to time, since we'll get to it the next time we're called.  We're called repeatedly
207    // and frequently (around every 3ms).  The background thread is processing well into the future and has a considerable amount of
208    // leeway here...
209    if (m_backgroundThreadLock.tryLock()) {
210        m_moreInputBuffered = true;
211        m_backgroundThreadCondition.signal();
212        m_backgroundThreadLock.unlock();
213    }
214}
215
216void ReverbConvolver::reset()
217{
218    for (size_t i = 0; i < m_stages.size(); ++i)
219        m_stages[i]->reset();
220
221    for (size_t i = 0; i < m_backgroundStages.size(); ++i)
222        m_backgroundStages[i]->reset();
223
224    m_accumulationBuffer.reset();
225    m_inputBuffer.reset();
226}
227
228} // namespace WebCore
229
230#endif // ENABLE(WEB_AUDIO)
231