Pan / Balance control of multi-channel Audio
This may be a stupid question but where is the per channel level controls on the QMediaPlayerControl and other similar classes that process audio stream that can have more than one audio channel? Fair enough the "volume" control provides an overall gain control but how can I (re)position that audio stream say to achieve a "balance" control for a stereo audio stream - or if, say, I was writing a game, how can I position a (monoaural) sound effect within, say a four speaker arrangement to tell the player that he has just been shot in the back or right side? It seems that the controls that would be required for this are missing - or have I just been looking in the wrong part of the C++ API?
Mixing audio channels is (at least currently) outside of Qt's scope
Well "mixing" is a closely related function I suppose if one was dealing with more than one audio data source - but this is more a query of that somehow we do have a single control of the overall level of all channels of an audio stream but not a means of controlling the relative levels of each channel. I was looking for what https://bugreports.qt-project.org/browse/QTBUG-23808 calls "Panning Support" and I think the dropped Phonon had an Effect class that may have provided a way to do this.
With regard to the "(at least currently)" are you aware of a specific Bug/Feature Request that is tracking this - I couldn't spot one but I may not have been searching for the right thing...
No I'm not aware of a bug related to that
As for Phonon, IIRC, there's a possibility to build it for Qt 5 if that would help your current project.