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/*  This file is part of the KDE project
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    Copyright (C) 2006 Matthias Kretz <kretz@kde.org>
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    This library is free software; you can redistribute it and/or
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    modify it under the terms of the GNU Lesser General Public
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    License as published by the Free Software Foundation; either
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    version 2.1 of the License, or (at your option) version 3, or any
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    later version accepted by the membership of KDE e.V. (or its
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    successor approved by the membership of KDE e.V.), Nokia Corporation 
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    (or its successors, if any) and the KDE Free Qt Foundation, which shall
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    act as a proxy defined in Section 6 of version 3 of the license.
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    This library is distributed in the hope that it will be useful,
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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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    Lesser General Public License for more details.
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    You should have received a copy of the GNU Lesser General Public 
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    License along with this library.  If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef PHONON_VOLUMEFADEREFFECT_H
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#define PHONON_VOLUMEFADEREFFECT_H
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#include "phonon_export.h"
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#include "effect.h"
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QT_BEGIN_HEADER
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QT_BEGIN_NAMESPACE
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#ifndef QT_NO_PHONON_VOLUMEFADEREFFECT
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namespace Phonon
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{
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    class VolumeFaderEffectPrivate;
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    /** \class VolumeFaderEffect volumefadereffect.h Phonon/VolumeFaderEffect
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     * Audio effect to gradually fade the audio volume.
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     *
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     * This effect differs from gradually changing the output volume in that
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     * a dedicated effect can change the volume in the smallest possible
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     * steps while every other volume control will make more or less
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     * noticeable steps.
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     *
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     * \ingroup PhononEffects
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     * \author Matthias Kretz <kretz@kde.org>
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     * \see AudioOutput::volume
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     */
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    class PHONON_EXPORT VolumeFaderEffect : public Effect
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    {
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        Q_OBJECT
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        K_DECLARE_PRIVATE(VolumeFaderEffect)
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        PHONON_HEIR(VolumeFaderEffect)
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        Q_ENUMS(FadeCurve)
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        /**
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         * This is the current volume of the output as voltage factor.
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         * Setting this property changes the volume immediately.
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         *
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         * 1.0 means 100%, 0.5 means 50% voltage/25% power, 0.0 means 0%
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         *
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         * \see volumeDecibel
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         */
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        Q_PROPERTY(float volume READ volume WRITE setVolume)
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        /**
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         * This is the current volume of the output in decibel.
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         * Setting this property changes the volume immediately.
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         *
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         * 0 dB means no change in volume, -6dB means an attenuation of the
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         * voltage to 50% and an attenuation of the power to 25%, -inf dB means
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         * silence.
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         *
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         * \see volume
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         */
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        Q_PROPERTY(double volumeDecibel READ volumeDecibel WRITE setVolumeDecibel)
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        /**
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         * This property holds the fade curve to be used for the fadeIn(), fadeOut()
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         * and fadeTo() slots.
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         *
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         * Defaults to Fade3Decibel.
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         *
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         * \see FadeCurve
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         */
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        Q_PROPERTY(FadeCurve fadeCurve READ fadeCurve WRITE setFadeCurve)
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        public:
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            /**
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             * Determines the curve of the volume change.
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             */
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            enum FadeCurve {
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                /**
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                 * "Crossfade curve" / "fast" fade out
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                 *
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                 * Often the best fade for a crossfade, as after half of the
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                 * time the volume reached -3dB. This means that half the
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                 * possible power (which is proportional to the square of the
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                 * voltage) is reached. Summed, the maximum power of two audio
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                 * signals fading with a -3dB curve will always be equal.
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                 *
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                 * For fading in or out the -3dB curve is too abrupt in the end.
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                 *
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                 * This is the default fade curve.
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                 */
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                Fade3Decibel,
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                /**
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                 * "Linear" fade out
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                 *
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                 * With a -6dB fade curve after half of the fading time -6dB has
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                 * been reached. -6dB is equal to half of the voltage meaning
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                 * that the voltage multiplier changes linearly from the start
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                 * of the fade to the end.
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                 */
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                Fade6Decibel,
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                /**
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                 * "slow" fade out
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                 *
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                 * After half of the fade time -9dB are reached. So the fade is
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                 * fast in the beginning and slow in the end. This is a good
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                 * fade for ending music.
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                 */
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                Fade9Decibel,
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                /**
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                 * more extreme version of the -9dB fade
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                 */
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                Fade12Decibel
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            };
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            float volume() const;
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            double volumeDecibel() const;
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            FadeCurve fadeCurve() const;
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        public Q_SLOTS:
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            /**
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             * Tells the Fader to change the volume from the current volume to 100%
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             * in \p fadeTime milliseconds.
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             * Short for \c fadeTo(1.0, fadeTime).
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             *
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             * \param fadeTime the fade duration in milliseconds
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             *
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             * \see fadeTo
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             * \see volume
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             */
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            void fadeIn(int fadeTime);
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            /**
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             * Tells the Fader to change the volume from the current volume to 0%
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             * in \p fadeTime milliseconds.
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             * Short for \c fadeTo(0.0, fadeTime).
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             *
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             * \param fadeTime the fade duration in milliseconds
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             *
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             * \see fadeTo
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             */
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            void fadeOut(int fadeTime);
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            void setVolume(float volume);
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            void setVolumeDecibel(double volumeDecibel);
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            void setFadeCurve(FadeCurve curve);
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            /**
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             * Tells the Fader to change the volume from the current value to
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             * \p volume in \p fadeTime milliseconds
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             *
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             * \see fadeIn
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             * \see fadeOut
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             */
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            void fadeTo(float volume, int fadeTime);
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    };
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} //namespace Phonon
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#endif //QT_NO_PHONON_VOLUMEFADEREFFECT
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QT_END_NAMESPACE
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QT_END_HEADER
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// vim: sw=4 ts=4 tw=80
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#endif // PHONON_VOLUMEFADEREFFECT_H