tor-browser

ReverbConvolver.cpp (11382B)

---

/*
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#include "ReverbConvolver.h"

#include "ReverbConvolverStage.h"

using namespace mozilla;

namespace WebCore {

const int InputBufferSize = 8 * 16384;

// We only process the leading portion of the impulse response in the real-time
// thread.  We don't exceed this length. It turns out then, that the background
// thread has about 278msec of scheduling slop. Empirically, this has been found
// to be a good compromise between giving enough time for scheduling slop, while
// still minimizing the amount of processing done in the primary (high-priority)
// thread. This was found to be a good value on Mac OS X, and may work well on
// other platforms as well, assuming the very rough scheduling latencies are
// similar on these time-scales.  Of course, this code may need to be tuned for
// individual platforms if this assumption is found to be incorrect.
const size_t RealtimeFrameLimit = 8192 + 4096  // ~278msec @ 44.1KHz
                                 - WEBAUDIO_BLOCK_SIZE;
// First stage will have size MinFFTSize - successive stages will double in
// size each time until we hit the maximum size.
const size_t MinFFTSize = 256;
// If we are using background threads then don't exceed this FFT size for the
// stages which run in the real-time thread.  This avoids having only one or
// two large stages (size 16384 or so) at the end which take a lot of time
// every several processing slices.  This way we amortize the cost over more
// processing slices.
const size_t MaxRealtimeFFTSize = 4096;

ReverbConvolver::ReverbConvolver(const float* impulseResponseData,
                                size_t impulseResponseLength,
                                size_t maxFFTSize, size_t convolverRenderPhase,
                                bool useBackgroundThreads,
                                bool* aAllocationFailure)
   : m_impulseResponseLength(impulseResponseLength),
     m_inputBuffer(InputBufferSize),
     m_backgroundThread("ConvolverWorker"),
     m_backgroundThreadMonitor("ConvolverMonitor"),
     m_useBackgroundThreads(useBackgroundThreads),
     m_wantsToExit(false),
     m_moreInputBuffered(false) {
 *aAllocationFailure = !m_accumulationBuffer.allocate(impulseResponseLength +
                                                      WEBAUDIO_BLOCK_SIZE);
 if (*aAllocationFailure) {
   return;
 }
 // For the moment, a good way to know if we have real-time constraint is to
 // check if we're using background threads. Otherwise, assume we're being run
 // from a command-line tool.
 bool hasRealtimeConstraint = useBackgroundThreads;

 const float* response = impulseResponseData;
 size_t totalResponseLength = impulseResponseLength;

 // The total latency is zero because the first FFT stage is small enough
 // to return output in the first block.
 size_t reverbTotalLatency = 0;

 size_t stageOffset = 0;
 size_t stagePhase = 0;
 size_t fftSize = MinFFTSize;
 while (stageOffset < totalResponseLength) {
   size_t stageSize = fftSize / 2;

   // For the last stage, it's possible that stageOffset is such that we're
   // straddling the end of the impulse response buffer (if we use stageSize),
   // so reduce the last stage's length...
   if (stageSize + stageOffset > totalResponseLength) {
     stageSize = totalResponseLength - stageOffset;
     // Use smallest FFT that is large enough to cover the last stage.
     fftSize = MinFFTSize;
     while (stageSize * 2 > fftSize) {
       fftSize *= 2;
     }
   }

   // This "staggers" the time when each FFT happens so they don't all happen
   // at the same time
   int renderPhase = convolverRenderPhase + stagePhase;

   UniquePtr<ReverbConvolverStage> stage(new ReverbConvolverStage(
       response, totalResponseLength, reverbTotalLatency, stageOffset,
       stageSize, fftSize, renderPhase, &m_accumulationBuffer));

   bool isBackgroundStage = false;

   if (this->useBackgroundThreads() && stageOffset > RealtimeFrameLimit) {
     m_backgroundStages.AppendElement(std::move(stage));
     isBackgroundStage = true;
   } else
     m_stages.AppendElement(std::move(stage));

   // Figure out next FFT size
   fftSize *= 2;

   stageOffset += stageSize;

   if (hasRealtimeConstraint && !isBackgroundStage &&
       fftSize > MaxRealtimeFFTSize) {
     fftSize = MaxRealtimeFFTSize;
     // Custom phase positions for all but the first of the realtime
     // stages of largest size.  These spread out the work of the
     // larger realtime stages.  None of the FFTs of size 1024, 2048 or
     // 4096 are performed when processing the same block.  The first
     // MaxRealtimeFFTSize = 4096 stage, at the end of the doubling,
     // performs its FFT at block 7.  The FFTs of size 2048 are
     // performed in blocks 3 + 8 * n and size 1024 at 1 + 4 * n.
     const uint32_t phaseLookup[] = {14, 0, 10, 4};
     stagePhase = WEBAUDIO_BLOCK_SIZE *
                  phaseLookup[m_stages.Length() % std::size(phaseLookup)];
   } else if (fftSize > maxFFTSize) {
     fftSize = maxFFTSize;
     // A prime offset spreads out FFTs in a way that all
     // available phase positions will be used if there are sufficient
     // stages.
     stagePhase += 5 * WEBAUDIO_BLOCK_SIZE;
   } else if (stageSize > WEBAUDIO_BLOCK_SIZE) {
     // As the stages are doubling in size, the next FFT will occur
     // mid-way between FFTs for this stage.
     stagePhase = stageSize - WEBAUDIO_BLOCK_SIZE;
   }
 }

 // Start up background thread
 // FIXME: would be better to up the thread priority here.  It doesn't need to
 // be real-time, but higher than the default...
 if (this->useBackgroundThreads() && m_backgroundStages.Length() > 0) {
   if (!m_backgroundThread.Start()) {
     NS_WARNING("Cannot start convolver thread.");
     return;
   }
   m_backgroundThread.message_loop()->PostTask(NewNonOwningRunnableMethod(
       "WebCore::ReverbConvolver::backgroundThreadEntry", this,
       &ReverbConvolver::backgroundThreadEntry));
 }
}

ReverbConvolver::~ReverbConvolver() {
 // Wait for background thread to stop
 if (useBackgroundThreads() && m_backgroundThread.IsRunning()) {
   m_wantsToExit = true;

   // Wake up thread so it can return
   {
     MonitorAutoLock locker(m_backgroundThreadMonitor);
     m_moreInputBuffered = true;
     m_backgroundThreadMonitor.Notify();
   }

   m_backgroundThread.Stop();
 }
}

size_t ReverbConvolver::sizeOfIncludingThis(
   mozilla::MallocSizeOf aMallocSizeOf) const {
 size_t amount = aMallocSizeOf(this);
 amount += m_stages.ShallowSizeOfExcludingThis(aMallocSizeOf);
 for (size_t i = 0; i < m_stages.Length(); i++) {
   if (m_stages[i]) {
     amount += m_stages[i]->sizeOfIncludingThis(aMallocSizeOf);
   }
 }

 amount += m_backgroundStages.ShallowSizeOfExcludingThis(aMallocSizeOf);
 for (size_t i = 0; i < m_backgroundStages.Length(); i++) {
   if (m_backgroundStages[i]) {
     amount += m_backgroundStages[i]->sizeOfIncludingThis(aMallocSizeOf);
   }
 }

 // NB: The buffer sizes are static, so even though they might be accessed
 //     in another thread it's safe to measure them.
 amount += m_accumulationBuffer.sizeOfExcludingThis(aMallocSizeOf);
 amount += m_inputBuffer.sizeOfExcludingThis(aMallocSizeOf);

 // Possible future measurements:
 // - m_backgroundThread
 // - m_backgroundThreadMonitor
 return amount;
}

void ReverbConvolver::backgroundThreadEntry() {
 while (!m_wantsToExit) {
   // Wait for realtime thread to give us more input
   m_moreInputBuffered = false;
   {
     MonitorAutoLock locker(m_backgroundThreadMonitor);
     while (!m_moreInputBuffered && !m_wantsToExit)
       m_backgroundThreadMonitor.Wait();
   }

   // Process all of the stages until their read indices reach the input
   // buffer's write index
   int writeIndex = m_inputBuffer.writeIndex();

   // Even though it doesn't seem like every stage needs to maintain its own
   // version of readIndex we do this in case we want to run in more than one
   // background thread.
   int readIndex;

   while ((readIndex = m_backgroundStages[0]->inputReadIndex()) !=
          writeIndex) {  // FIXME: do better to detect buffer overrun...
     // Accumulate contributions from each stage
     for (size_t i = 0; i < m_backgroundStages.Length(); ++i)
       m_backgroundStages[i]->processInBackground(this);
   }
 }
}

void ReverbConvolver::process(const float* sourceChannelData,
                             float* destinationChannelData) {
 const float* source = sourceChannelData;
 float* destination = destinationChannelData;
 bool isDataSafe = source && destination;
 MOZ_ASSERT(isDataSafe);
 if (!isDataSafe) return;

 // Feed input buffer (read by all threads)
 m_inputBuffer.write(source, WEBAUDIO_BLOCK_SIZE);

 // Accumulate contributions from each stage
 for (size_t i = 0; i < m_stages.Length(); ++i) m_stages[i]->process(source);

 // Finally read from accumulation buffer
 m_accumulationBuffer.readAndClear(destination, WEBAUDIO_BLOCK_SIZE);

 // Now that we've buffered more input, wake up our background thread.

 // Not using a MonitorAutoLock looks strange, but we use a TryLock() instead
 // because this is run on the real-time thread where it is a disaster for the
 // lock to be contended (causes audio glitching).  It's OK if we fail to
 // signal from time to time, since we'll get to it the next time we're called.
 // We're called repeatedly and frequently (around every 3ms).  The background
 // thread is processing well into the future and has a considerable amount of
 // leeway here...
 if (m_backgroundThreadMonitor.TryLock()) {
   m_moreInputBuffered = true;
   m_backgroundThreadMonitor.Notify();
   m_backgroundThreadMonitor.Unlock();
 }
}

}  // namespace WebCore