[SailfishDevel] Updates to resource policy implementation in QtMultimedia (update8)

[Martin Windolph]

Hi,

thanks! That really sounds like I can update my game (Morzyn) in the near future to activate sound again.

But I have a question regarding volume behavior:

You wrote:
"Unless volume or category is explicitly set for the classes, all follow 
system media volume (changed with the hardware volume keys)."

I like to fade the game main menu music (mp3) in and out. So I use an animation on
the volume property of my Audio-QML-Object. So I set the volume explicitely from 100% to 0% (fade out) and from 0% to 100% (fade in). 

When system volume is eg. about 30%, does that mean that my menu music "global" volume fades from 30% to 0% or from 100% to 0%? 30% to 0% would be correct in my opinion...it also does so on Windows and Android.
For the SoundEffects (wav) I don't change the volume. So they should be 30% (following system volume).

BR
Martin


> Date: Thu, 3 Jul 2014 13:57:36 +0300
> From: juho.hamalainen at tieto.com
> To: devel at lists.sailfishos.org
> Subject: [SailfishDevel] Updates to resource policy implementation in	QtMultimedia (update8)
> 
> Updates to resource policy implementation in QtMultimedia
> =========================================================
> 
> In next update (update8) there will be QtMultimedia with updates to the 
> resource policy implementation. The goal of these resource policy 
> implementation changes is to allow easier and simpler use of Qt/QML 
> audio APIs while behind the scene playing nicely with the system 
> resource manager.
> 
> There are three types of Qt classes for audio handling with resource 
> policy implementation,
>   * QMediaPlayer  [1]
>   * QSoundEffect  [2]
>   * QAudioOutput  [3]
> 
> There are two QML types for use with resource policy implementation
>   * Audio  [4]
>   * SoundEffect  [5]
> 
> In real life applications only QAudioOutput functionality changes 
> noticeably (QAudioOutput didn't have any resource policy support 
> previously), QMediaPlayer has already resource policy support and 
> QSoundEffect resource policy support is improved.
> 
> QMediaPlayer / Audio
> ====================
> 
> This class is meant for playing longer audio files, for example if 
> implementing media player or background music for game.
> 
> When QMediaPlayer object is created, it will automatically connect to 
> the resource manager in the background and is immediately ready to use. 
> When setting the object to playing state, QMediaPlayer internally tries 
> to acquire resources for the application, and if resources are aqcuired, 
> playback starts immediately. Otherwise playback will stall. When 
> QMediaPlayer is in end of media or set to paused or stopped, after 2 
> second timeout the object will release resources it has acquired.
> 
> QSoundEffect / SoundEffect
> ==========================
> 
> This class is meant for playing short sound effects, for example 
> application UI clicks or other notifications, game sounds, etc. All 
> sound effect type sounds are mixed on top of other sounds, so there can 
> be media player playing music while sound effects are played.
> 
> When QSoundEffect object is created, it will automatically connect to 
> the resource manager in the background and is immediately ready to use. 
> When higher priority application is active (voice call, ringtone), 
> calling play for the object does nothing. When no higher priority 
> applications are active, or media player object is active, sound effect 
> is played.
> 
> QAudioOutput
> ============
> 
> This class is meant for example when audio data is streamed.
> 
> When QAudioOutput object is created, it will automatically connect to 
> the resource manager in the background and is immediately ready to use. 
>   When setting the object to playing state, QAudioOutput internally 
> tries to acquire resources for the application, and if resources are 
> aqcuired, playback starts immediately. Otherwise playback will stall. 
> When QAudioOutput is set to paused or stopped state, after 2 second 
> timeout the object will release resources it has acquired.
> 
> Notes for both QMediaPlayer and QAudioOutput
> ============================================
> 
> User needs to  follow state changed signals from the object, since the 
> change can  happen even without interaction with the application itself. 
> (Other application acquires resources, voice call acquires resources)
> 
> Only one media player or audio output object can be in playing state at 
> given time. Last object acquiring resources gets the resources.
> 
> Short note about volume behavior
> ================================
> 
> Unless volume or category is explicitly set for the classes, all follow 
> system media volume (changed with the hardware volume keys).
> 
> 
> [1] http://doc.qt.digia.com/qt-5.1/qtmultimedia/qmediaplayer.html
> [2] http://doc.qt.digia.com/qt-5.1/qtmultimedia/qsoundeffect.html
> [3] http://doc.qt.digia.com/qt-5.1/qtmultimedia/qaudiooutput.html
> [4] http://doc.qt.digia.com/qt-5.1/qtmultimedia/qml-qtmultimedia5-audio.html
> [5] 
> http://doc.qt.digia.com/qt-5.1/qtmultimedia/qml-qtmultimedia5-soundeffect.html
> 
> 
> Regards,
> Juho Hämäläinen / jusa_
> 
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