diff options
Diffstat (limited to 'src/imports/multimedia/qdeclarativemultimediaglobal.cpp')
-rw-r--r-- | src/imports/multimedia/qdeclarativemultimediaglobal.cpp | 53 |
1 files changed, 53 insertions, 0 deletions
diff --git a/src/imports/multimedia/qdeclarativemultimediaglobal.cpp b/src/imports/multimedia/qdeclarativemultimediaglobal.cpp index b2a1aed12..999f086d5 100644 --- a/src/imports/multimedia/qdeclarativemultimediaglobal.cpp +++ b/src/imports/multimedia/qdeclarativemultimediaglobal.cpp @@ -183,4 +183,57 @@ QJSValue QDeclarativeMultimediaGlobal::availableCameras() const return availableCameras; } +/*! + \qmlmethod real QtMultimedia::QtMultimedia::convertVolume(real volume, VolumeScale from, VolumeScale to) + + Converts an audio \a volume \a from a volume scale \a to another, and returns the result. + + Depending on the context, different scales are used to represent audio volume. All Qt Multimedia + classes that have an audio volume use a linear scale, the reason is that the loudness of a + speaker is controlled by modulating its voltage on a linear scale. The human ear on the other + hand, perceives loudness in a logarithmic way. Using a logarithmic scale for volume controls + is therefore appropriate in most applications. The decibel scale is logarithmic by nature and + is commonly used to define sound levels, it is usually used for UI volume controls in + professional audio applications. The cubic scale is a computationally cheap approximation of a + logarithmic scale, it provides more control over lower volume levels. + + Valid values for \a from and \a to are: + \list + \li QtMultimedia.LinearVolumeScale - Linear scale. \c 0.0 (0%) is silence and \c 1.0 (100%) is + full volume. All Qt Multimedia types that have an audio volume use a linear scale. + \li QtMultimedia.CubicVolumeScale - Cubic scale. \c 0.0 (0%) is silence and \c 1.0 (100%) is full + volume. + \li QtMultimedia.LogarithmicVolumeScale - Logarithmic scale. \c 0.0 (0%) is silence and \c 1.0 + (100%) is full volume. UI volume controls should usually use a logarithmic scale. + \li QtMultimedia.DecibelVolumeScale - Decibel (dB, amplitude) logarithmic scale. \c -200 is + silence and \c 0 is full volume. + \endlist + + The following example shows how the volume value from a UI volume control can be converted so + that the perceived increase in loudness is the same when increasing the volume control from 0.2 + to 0.3 as it is from 0.5 to 0.6: + + \code + Slider { + id: volumeSlider + + property real volume: QtMultimedia.convertVolume(volumeSlider.value, + QtMultimedia.LogarithmicVolumeScale, + QtMultimedia.LinearVolumeScale) + } + + MediaPlayer { + volume: volumeSlider.volume + } + \endcode + + \since 5.8 +*/ +qreal QDeclarativeMultimediaGlobal::convertVolume(qreal volume, + QDeclarativeMultimediaGlobal::VolumeScale from, + QDeclarativeMultimediaGlobal::VolumeScale to) const +{ + return QAudio::convertVolume(volume, QAudio::VolumeScale(from), QAudio::VolumeScale(to)); +} + QT_END_NAMESPACE |