It messes with 5.1 sources using direct channels, and the surround channels are
supposed to map to the side labels. Individual backends can deal with the
channel order/label differences, as they already do to a degree.
If setting the requested format channel count fails, getting anything with 2 or
more channels assumes the first two channels are stereo, leaving the rest
silent.
The itu5.1-nocenter preset is the same as the previous default, so it can still
be used for people that prefer it. But this new one purportedly has better
panning and positioning responses in listening tests, which initial impressions
concur with.
It's inconsistent behavior with spatialized B-Format sources, and causes a very
apparent gain disparity between such a source on the listener compared to just
barely off-origin. It's also not something an app can easy correct for if it
doesn't want that behavior, since the source gain clamps to 1 by default. In
contrast, an app can attenuate sources as they want with little issue.
AudioBufferList contains a variable length array of mNumberBuffers elements, so it should not be created with the default constructor like usual class instances.
Unfortunately, Apple developer site documentation is literally empty for this API. There is a bunch of comments in framework's header files.
Here is the correct usage of AudioBufferList pointer from Chromium: 008a1abc57/audio/mac/audio_manager_mac.cc (266)
There were occasional crashes because of memory corruption which was confirmed by address sanitizer
It's too unstable with larger vectors. Even when the source and listener
positions are the same, floating point precision can cause noticeable rounding
errors.
Rather than stopping voices/sources when the device becomes disconnected, the
context can be set to leave them alone. As a consequence, their state will
remain as playing and they'll keep their last known sample offset indefinately.
For applications mindful of this behavior, it will allow resetting or reopening
the device to reconnect and automatically resume where it left off.
