Split "Online" and "Offline" AudioContext processing

Source/platform/audio/ReverbConvolver.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 39 matching lines @@
 // 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
 
 const size_t MinFFTSize = 128;
 const size_t MaxRealtimeFFTSize = 2048;
 
-ReverbConvolver::ReverbConvolver(AudioChannel* impulseResponse, size_t renderSliceSize, size_t maxFFTSize, size_t convolverRenderPhase, bool useBackgroundThreads)
+ReverbConvolver::ReverbConvolver(AudioChannel* impulseResponse, size_t renderSliceSize, size_t maxFFTSize, size_t convolverRenderPhase, bool hasRealtimeConstraint)
     : m_impulseResponseLength(impulseResponse->length())
     , m_accumulationBuffer(impulseResponse->length() + renderSliceSize)
     , m_inputBuffer(InputBufferSize)
     , m_minFFTSize(MinFFTSize) // First stage will have this size - successive stages will double in size each time
     , m_maxFFTSize(maxFFTSize) // until we hit m_maxFFTSize
 {
     // 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.
     m_maxRealtimeFFTSize = MaxRealtimeFFTSize;
 
-    // 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 = impulseResponse->data();
     size_t totalResponseLength = impulseResponse->length();
 
     // The total latency is zero because the direct-convolution is used in the leading portion.
     size_t reverbTotalLatency = 0;
 
     size_t stageOffset = 0;
     int i = 0;
     size_t fftSize = m_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;
 
         // This "staggers" the time when each FFT happens so they don't all happen at the same time
         int renderPhase = convolverRenderPhase + i * renderSliceSize;
 
         bool useDirectConvolver = !stageOffset;
 
         OwnPtr<ReverbConvolverStage> stage = adoptPtr(new ReverbConvolverStage(response, totalResponseLength, reverbTotalLatency, stageOffset, stageSize, fftSize, renderPhase, renderSliceSize, &m_accumulationBuffer, useDirectConvolver));
 
         bool isBackgroundStage = false;
 
-        if (useBackgroundThreads && stageOffset > RealtimeFrameLimit) {
+        if (hasRealtimeConstraint && stageOffset > RealtimeFrameLimit) {
             m_backgroundStages.append(stage.release());
             isBackgroundStage = true;
         } else
             m_stages.append(stage.release());
 
         stageOffset += stageSize;
         ++i;
 
         if (!useDirectConvolver) {
             // Figure out next FFT size
             fftSize *= 2;
         }
 
         if (hasRealtimeConstraint && !isBackgroundStage && fftSize > m_maxRealtimeFFTSize)
             fftSize = m_maxRealtimeFFTSize;
         if (fftSize > m_maxFFTSize)
             fftSize = m_maxFFTSize;
     }
 
     // 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 (useBackgroundThreads && m_backgroundStages.size() > 0)
+    if (hasRealtimeConstraint && m_backgroundStages.size() > 0)
         m_backgroundThread = adoptPtr(Platform::current()->createThread("Reverb convolution background thread"));
 }
 
 ReverbConvolver::~ReverbConvolver()
 {
     // Wait for background thread to stop
     m_backgroundThread.clear();
 }
 
 void ReverbConvolver::processInBackground()
@@ skipping 57 matching lines @@
 }
 
 size_t ReverbConvolver::latencyFrames() const
 {
     return 0;
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)