[pulseaudio-tickets] [Bug 90027] Switching from A2DP to HSP produces noise

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=90027

--- Comment #7 from Tanu Kaskinen <tanuk at iki.fi> ---
About configuring the adapter, here's some vague advice based on the discussion
on bug 97064 and some comments from Luiz in IRC (I'll add Luiz to CC):

PulseAudio requires the adapter to take the SCO audio via the HCI interface
(SCO is the audio protocol that is used in HSP). The noise might not be because
the adapter expects a different audio format than what pulseaudio sends, but
because the adapter's audio routing is wrong, and the audio that it sends to
the headset is coming from some interface that isn't connected to any real
audio source.

Configuring the adapter's SCO audio routing to use HCI is vendor-specific (and
I don't know if it's even possible for all adapters), so I can't give the exact
commands to do it. The discussion in bug 97064 may offer some hints. It's also
worth checking that there's no missing firmware (again, refer to the discussion
in bug 97064).

I'll add here my short discussion with Luiz in IRC:

<tanuk>   vudentz: Do you know what could cause only noise to be played
          when using HSP?
<vudentz> tanuk, nope, perhaps the controller is not really setup for HCI
          routing as PA expects?
<vudentz> SCO setup is quite tricky since no manufacturer really test
          their firmware properly, and on windows they might actually
          have other audio solutions
<tanuk>   vudentz: Based on the comments in another bug (97064), the
          audio routing setup seems to require vendor specific commands,
          so it's hard to give people good advice for how to do it...
<vudentz> tanuk, specially on phones/tablets controllers tend to be
          hardwired the pcm line, USB should normally use HCI but I heard
          about controllers using custom transports that use USB bulk
          endpoint instead of isochronous defined in the spec.

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