Seeking thoughts on real world application of SC 1.4.2 Audio Control on iOS

Hi gang,

For a (growing?) number of our success criteria, the underlying 
environment/platform provides support such that it is (no longer) 
necessary for the application to do anything special.  For example, it 
is no longer necessary for an application to be self-enlarging to meet 
SC 1.4.4 Resize Text 
<http://www.w3.org/TR/WCAG/#visual-audio-contrast-scale>, since 
virtually every current version of every browser will do this.  It is 
only necessary to not be incompatible with that browser feature.

Thinking now about SC 1.4.2 Audio Control 
<http://www.w3.org/TR/WCAG/#visual-audio-contrast-dis-audio>, 
specifically on iOS, I wonder if we may be in a similar situation.  When 
I am listening to audio on my iPhone (e.g. listening to a podcast or 
music), and I use VoiceOver to interact with the phone, while VoiceOver 
is speaking, it lowers the volume of whatever is playing so that 
VoiceOver's speech is clearly intelligible.  I haven't measured, but the 
volume difference may be as great as the 20 dB difference specified by 
the AAA SC 1.4.7 Low or No Background Audio 
<http://www.w3.org/TR/WCAG/#visual-audio-contrast-noaudio>.

So it seems VoiceOver/iOS is addressing the user need behind this SC; 
though perhaps not addressing it fully...?  I note that, at least in iOS 
v6.1.4 there doesn't seem to be an option to set the volume level that 
the "background" audio is lowered to, so the platform doesn't expose the 
full capability described in Understanding SC 1.4.2 
<http://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-dis-audio.html>. 


Anyway, I'm curious about the TF's thoughts on this.  Specifically:

  * Are we at least close to an analogous situation to SC 1.4.4, where
    an (iOS) app can rely on the underlying OS to handle the SC?  (of
    course you would test to ensure compatibility with the feature)
  * Whatever the specific requirements of the SC, have we fundamentally
    met the user need?  Or does anyone know of specific users for whom
    the built-in volume-lowering functionality of VoiceOver on iOS is
    insufficient?


Regards,

Peter

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