/*

 * 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

 *     notice, this list of conditions and the following disclaimer in the

 *     documentation and/or other materials provided with the distribution.

 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of

 *     its contributors may be used to endorse or promote products derived

 *     from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY

 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY

 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF

 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#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)

    : m_impulseResponseLength(impulseResponseLength)

    , m_accumulationBuffer(impulseResponseLength + WEBAUDIO_BLOCK_SIZE)

    , m_inputBuffer(InputBufferSize)

    , m_backgroundThread("ConvolverWorker")

    , m_backgroundThreadCondition(&m_backgroundThreadLock)

    , m_useBackgroundThreads(useBackgroundThreads)

    , m_wantsToExit(false)

    , m_moreInputBuffered(false)

{

    // 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;

        nsAutoPtr<ReverbConvolverStage> stage

          (new ReverbConvolverStage(response, totalResponseLength,

                                    reverbTotalLatency, stageOffset, stageSize,

                                    fftSize, renderPhase,

                                    &m_accumulationBuffer));

        bool isBackgroundStage = false;

        if (this->useBackgroundThreads() && stageOffset > RealtimeFrameLimit) {

            m_backgroundStages.AppendElement(stage.forget());

            isBackgroundStage = true;

        } else

            m_stages.AppendElement(stage.forget());

        // 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() % ArrayLength(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

        {

            AutoLock locker(m_backgroundThreadLock);

            m_moreInputBuffered = true;

            m_backgroundThreadCondition.Signal();

        }

        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_backgroundThreadLock

    // - m_backgroundThreadCondition

    return amount;

}

void ReverbConvolver::backgroundThreadEntry()

{

    while (!m_wantsToExit) {

        // Wait for realtime thread to give us more input

        m_moreInputBuffered = false;

        {

            AutoLock locker(m_backgroundThreadLock);

            while (!m_moreInputBuffered && !m_wantsToExit)

                m_backgroundThreadCondition.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 MutexLocker 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_backgroundThreadLock.Try()) {

        m_moreInputBuffered = true;

        m_backgroundThreadCondition.Signal();

        m_backgroundThreadLock.Release();

    }

}

} // namespace WebCore