[Qt-interest] Sound issues, CAudioOutput, Phonon

[Harri Pasanen]

Well, I want to stream audio and control the volume.  Someone suggested I 
should scale the samples, but that's like radio station deciding how loud I 
should listen.  They try to do it but the result is lossy.

http://labs.qt.nokia.com/2010/05/10/low-level-audio-processing-with-
qtmultimedia/

explicitly says that volume control should be there, but it is not yet 
implemented.  

Phonon has volume control, but my attempt to support streaming through
Phonon::MediaSource ( QIODevice * ioDevice ) failed, as that is not 
implemented.  Is there another way?

I ended up implementing my stuff using CMdaAudioOutputStream, which does 
support real time device volume control while streaming.   Unfortunately that 
is a Symbian specific API, so off the window went portability.

So for my use case to remain portable, I'd need either QAudioOutput volume 
control or Phonon streaming support.   So which one will be there first, and 
when can I expect it?



On Monday, November 15, 2010 11:14:38 am Constantin Makshin wrote:
> QtMultimedia is at lower level than Phonon, but not too low
> (http://doc.qt.nokia.com/4.7/qtmultimedia.html).
> 
> Also, Qt developers said new features will go to QtMultimedia and they seem
> to have no plans to include Phonon in Qt 5+ (well, a lot of time may pass
> until Qt5 is released, but anyway).
> http://labs.qt.nokia.com/2009/09/09/multimedia-in-qt-whats-the-story
> 
> And isn't Phonon::AudioOutput::setVolume[Decibel]() what you need?
> http://doc.qt.nokia.com/4.7/phonon-audiooutput.html#volume-prop
> http://doc.qt.nokia.com/4.7/phonon-audiooutput.html#volumeDecibel-prop
> 
> P.S.:
> Please send replies to the mailing list next time. Unless you want to start
> some private discussion, of course.
> 
> On Monday 15 November 2010 12:39:27 Keith Rusler wrote:
> > Isn't QtMultimedia abstract, meaning you have to write the audio stuff?
> > Because QtMultimedia is low level while Phonon is high level.
> > 
> > On 15 November 2010 03:28, Constantin Makshin <cmakshin at gmail.com> wrote:
> > > AFAIK, Phonon is deprecated in Qt and you should use QtMultimedia.
> > > 
> > > On Monday 15 November 2010 12:16:37 Harri Pasanen wrote:
> > > > Three issues:
> > > > 
> > > > I wonder when will CAudioOutput get volume control?
> > > > Btw. On Kubuntu 10.04 64 bit CAudioOutput did not seem to work at
> > > > all.
> > >  
> > >  There
> > >  
> > > > seemed to be a bug report for it already.
> > > > 
> > > > Phonon::MediaSource ( QIODevice * ioDevice ) does not seem to be
> > > 
> > > implemented,
> > > 
> > > > not when using Qt Simulator anyway.  Is that done in some more recent
> > > 
> > > version?

-- 
Grego
http://mpaja.com/