view audioio/AudioCallbackPlayTarget.h @ 148:7dca51571320 sv-v1.4rc1

* Ensure SimpleSPARQLQuery stores an error string properly when query
  fails -- so (apart from anything else) RDFImporter::identifyDocumentType
  returns a sensible result for non-RDF

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam.
    
    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.  See the file
    COPYING included with this distribution for more information.
*/

#ifndef _AUDIO_CALLBACK_PLAY_TARGET_H_
#define _AUDIO_CALLBACK_PLAY_TARGET_H_

#include <QObject>

class AudioCallbackPlaySource;

class AudioCallbackPlayTarget : public QObject
{
    Q_OBJECT

public:
    AudioCallbackPlayTarget(AudioCallbackPlaySource *source);
    virtual ~AudioCallbackPlayTarget();

    virtual bool isOK() const = 0;

    virtual void shutdown() = 0;

    virtual double getCurrentTime() const = 0;

    float getOutputGain() const {
	return m_outputGain;
    }

public slots:
    /**
     * Set the playback gain (0.0 = silence, 1.0 = levels unmodified)
     */
    virtual void setOutputGain(float gain);

    /**
     * The main source model (providing the playback sample rate) has
     * been changed.  The target should query the source's sample
     * rate, set its output sample rate accordingly, and call back on
     * the source's setTargetSampleRate to indicate what sample rate
     * it succeeded in setting at the output.  If this differs from
     * the model rate, the source will resample.
     */
    virtual void sourceModelReplaced() = 0;

protected:
    AudioCallbackPlaySource *m_source;
    float m_outputGain;
};

#endif