/home/maxime/Projets/Mixxx/1.10/mixxx/src/engine/enginesidechain.cpp

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/***************************************************************************
                          enginesidechain.cpp
                             -------------------
    copyright            : (C) 2008 Albert Santoni
    email                : gamegod \a\t users.sf.net
***************************************************************************/

/***************************************************************************
*                                                                         *
*   This program is free software; you can redistribute it and/or modify  *
*   it under the terms of the GNU General Public License as published by  *
*   the Free Software Foundation; either version 2 of the License, or     *
*   (at your option) any later version.                                   *
*                                                                         *
***************************************************************************/

/* This class provides a way to do audio processing that does not need
 * to be executed in real-time. For example, m_shoutcast encoding/broadcasting
 * and recording encoding can be done here. This class uses double-buffering
 * to increase the amount of time the CPU has to do whatever work needs to
 * be done, and that work is executed in a separate thread. (Threading
 * allows the next buffer to be filled while processing a buffer that's is
 * already full.)
 *
 */

#include <QtCore>
#include <QtDebug>

#include "engine/enginesidechain.h"
#include "engine/enginebuffer.h"
#include "recording/enginerecord.h"

#ifdef __SHOUTCAST__
#include "engine/engineshoutcast.h"
#endif

EngineSideChain::EngineSideChain(ConfigObject<ConfigValue> * pConfig) {
    m_pConfig = pConfig;
    m_bStopThread = false;

    m_bufferFront = new CSAMPLE[SIDECHAIN_BUFFER_SIZE];
    m_bufferBack  = new CSAMPLE[SIDECHAIN_BUFFER_SIZE];
    m_buffer = m_bufferFront;

    m_iBufferEnd = 0;

#ifdef __SHOUTCAST__
    // Shoutcast
        m_shoutcast = new EngineShoutcast(m_pConfig);
#endif

    m_rec = new EngineRecord(m_pConfig);
    connect(m_rec, SIGNAL(bytesRecorded(int)),
            this, SIGNAL(bytesRecorded(int)));
    connect(m_rec, SIGNAL(isRecording(bool)),
            this, SIGNAL(isRecording(bool)));


        start(QThread::LowPriority);    //Starts the thread and goes to the "run()" function below.
}

EngineSideChain::~EngineSideChain() {
    m_backBufferLock.lock();

    m_waitLock.lock();
    m_bStopThread = true;
    m_waitForFullBuffer.wakeAll();
    m_waitLock.unlock();

    wait(); //Wait until the thread has finished.

#ifdef __SHOUTCAST__
    if (m_shoutcast)
        m_shoutcast->shutdown();
#endif

    //Free up memory
    delete [] m_bufferFront;
    delete [] m_bufferBack;

#ifdef __SHOUTCAST__
    delete m_shoutcast;
#endif

    if(m_rec) delete m_rec;

    m_backBufferLock.unlock();
}

void EngineSideChain::submitSamples(CSAMPLE* newBuffer, int buffer_size)
{
    //Copy samples into m_buffer.
    if (m_iBufferEnd + buffer_size <= SIDECHAIN_BUFFER_SIZE)    //FIXME: is <= correct?
    {
        memcpy(&m_buffer[m_iBufferEnd], newBuffer, buffer_size * sizeof(CSAMPLE));
        m_iBufferEnd += buffer_size;
    }
    else //If the new buffer won't fit, copy as much of it as we can over and then copy the rest after swapping.
    {
        memcpy(&m_buffer[m_iBufferEnd], newBuffer, (SIDECHAIN_BUFFER_SIZE - m_iBufferEnd)*sizeof(CSAMPLE));
        //Save the number of samples written because m_iBufferEnd gets reset in swapBuffers:
        int iNumSamplesWritten = SIDECHAIN_BUFFER_SIZE - m_iBufferEnd;

        // This will block the callback thread if the buffering overflows. As of
        // 10/2009 this lock is only used to protect the buffer pointers, so it
        // won't cause blocking.
        m_backBufferLock.lock();
        swapBuffers(); //Swaps buffers and resets m_iBufferEnd to zero.
        m_backBufferLock.unlock();

        //Since we swapped buffers, we now have a full buffer that needs processing.
        m_waitForFullBuffer.wakeAll(); //... so wake the thread up and get processing. :)

        //Calculate how many leftover samples need to be written to the other buffer.
        int iNumSamplesStillToWrite = buffer_size - iNumSamplesWritten;

        //Check to see if the remaining samples will fit in the other empty buffer.
        if (iNumSamplesStillToWrite > SIDECHAIN_BUFFER_SIZE)
        {
            iNumSamplesStillToWrite = SIDECHAIN_BUFFER_SIZE; //Drop samples if they won't fit.
            qDebug() << "EngineSideChain warning: dropped samples";
        }
        memcpy(&m_buffer[m_iBufferEnd], &newBuffer[iNumSamplesWritten], iNumSamplesStillToWrite*sizeof(CSAMPLE));
        m_iBufferEnd += iNumSamplesStillToWrite;

    }
}

/* Swaps the buffers in the double-buffering mechanism we use */
void EngineSideChain::swapBuffers()
{
    if (m_buffer == m_bufferFront)
    {
        m_buffer = m_bufferBack;
        m_filledBuffer = m_bufferFront;
    }
    else
    {
        m_buffer = m_bufferFront;
        m_filledBuffer = m_bufferBack;
    }

    m_iBufferEnd = 0;
}

void EngineSideChain::run()
{
    unsigned static id = 0; //the id of this thread, for debugging purposes //XXX copypasta (should factor this out somehow), -kousu 2/2009
    QThread::currentThread()->setObjectName(QString("EngineSideChain %1").arg(++id));

    while (true)
    {
        m_waitLock.lock();
        // Check to see if we're supposed to exit/stop this thread.
        if (m_bStopThread) {
            m_waitLock.unlock();
            return;
        }
        m_waitForFullBuffer.wait(&m_waitLock);  //Sleep until the buffer has been filled.
        // Check to see if we're supposed to exit/stop this thread.
        if (m_bStopThread) {
            m_waitLock.unlock();
            return;
        }
        m_waitLock.unlock();

        //This portion of the code should be able to touch the buffer without having to use
        //the m_bufferLock mutex, because the buffers should have been swapped.

        //IMPORTANT: The filled buffer is "m_filledBuffer" - that's the audio we need to process here.

        //Do CPU intensive and non-realtime processing here.

        //m_backBufferLock.lock(); //This will cause the audio/callback thread to block if the buffers overflow,
                                   //so don't even think about enabling this. (I'm leaving it here as a
                                   //warning to anyone who wants to work on this code in the future.) - Albert

        // We need to use this lock when copying the pointer to the buffer or
        // else we could end up with a bogus pointer. We don't have to hold the
        // lock during the processing though.

        m_backBufferLock.lock();
        CSAMPLE* pBuffer = m_filledBuffer;
        m_backBufferLock.unlock();

#ifdef __SHOUTCAST__
        m_shoutcast->process(pBuffer, pBuffer, SIDECHAIN_BUFFER_SIZE);
#endif
        m_rec->process(pBuffer, pBuffer, SIDECHAIN_BUFFER_SIZE);
        //m_backBufferLock.unlock();
    }

}