examples/appsink-src/main.cpp

This example demonstrates how to use QGst::Utils::ApplicationSource and QGst::Utils::ApplicationSink to create a custom source and sink respectively.

In this example, we have two pipelines, one pipeline that gets data from a file, decodes the audio stream and sends the audio buffers to appsink, and a second pipeline that gets data from appsrc and pushes them to an audio sink. Appsink from the first pipeline is linked with appsrc from the second pipeline in our code, by listening to appsink's newBuffer() signal, getting the buffer and pushing it to appsrc with the pushBuffer() method. The result is a choppy audio player.

/*
    Copyright (C) 2011 Collabora Ltd. <info@collabora.co.uk>
      @author George Kiagiadakis <george.kiagiadakis@collabora.co.uk>

    This library is free software; you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published
    by the Free Software Foundation; either version 2.1 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/
#include <iostream>
#include <QCoreApplication>
#include <QGlib/Error>
#include <QGlib/Connect>
#include <QGst/Init>
#include <QGst/Bus>
#include <QGst/Pipeline>
#include <QGst/Parse>
#include <QGst/Message>
#include <QGst/Utils/ApplicationSink>
#include <QGst/Utils/ApplicationSource>


class MySink : public QGst::Utils::ApplicationSink
{
public:
    MySink(QGst::Utils::ApplicationSource *src)
        : QGst::Utils::ApplicationSink(), m_src(src) {}

protected:
    virtual void eos()
    {
        m_src->endOfStream();
    }

    virtual QGst::FlowReturn newSample()
    {
        QGst::SamplePtr sample = pullSample();
        m_src->pushBuffer(sample->buffer());
        return QGst::FlowOk;
    }

private:
    QGst::Utils::ApplicationSource *m_src;
};


class Player : public QCoreApplication
{
public:
    Player(int argc, char **argv);
    ~Player();

private:
    void onBusMessage(const QGst::MessagePtr & message);

private:
    QGst::Utils::ApplicationSource m_src;
    MySink m_sink;
    QGst::PipelinePtr pipeline1;
    QGst::PipelinePtr pipeline2;
};

Player::Player(int argc, char **argv)
    : QCoreApplication(argc, argv), m_sink(&m_src)
{
    QGst::init(&argc, &argv);

    if (argc <= 1) {
        std::cerr << "Usage: " << argv[0] << " <audio_file>" << std::endl;
        std::exit(1);
    }

    const char *caps = "audio/x-raw, format=(string)S16LE, channels=(int)1,"
                       " rate=(int)44100, layout=(string)interleaved";

    /* source pipeline */
    QString pipe1Descr = QString("filesrc location=\"%1\" ! "
                                 "decodebin ! "
                                 "audioconvert ! "
                                 "audioresample ! "
                                 "appsink name=\"mysink\" caps=\"%2\"").arg(argv[1], caps);
    pipeline1 = QGst::Parse::launch(pipe1Descr).dynamicCast<QGst::Pipeline>();
    m_sink.setElement(pipeline1->getElementByName("mysink"));
    QGlib::connect(pipeline1->bus(), "message::error", this, &Player::onBusMessage);
    pipeline1->bus()->addSignalWatch();

    /* sink pipeline */
    QString pipe2Descr = QString("appsrc name=\"mysrc\" caps=\"%1\" is-live=true format=3 ! "
                                 "autoaudiosink").arg(caps);
    pipeline2 = QGst::Parse::launch(pipe2Descr).dynamicCast<QGst::Pipeline>();
    m_src.setElement(pipeline2->getElementByName("mysrc"));
    QGlib::connect(pipeline2->bus(), "message", this, &Player::onBusMessage);
    pipeline2->bus()->addSignalWatch();

    /* start playing */
    pipeline1->setState(QGst::StatePlaying);
    pipeline2->setState(QGst::StatePlaying);
}

Player::~Player()
{
    pipeline1->setState(QGst::StateNull);
    pipeline2->setState(QGst::StateNull);
}

void Player::onBusMessage(const QGst::MessagePtr & message)
{
    switch (message->type()) {
    case QGst::MessageEos:
        quit();
        break;
    case QGst::MessageError:
        qCritical() << message.staticCast<QGst::ErrorMessage>()->error();
        break;
    default:
        break;
    }
}


int main(int argc, char **argv)
{
    Player p(argc, argv);
    return p.exec();
}