Oh Nine Fifteen

Post Syndicated from Lennart Poettering original https://0pointer.net/blog/projects/oh-nine-fifteen.html

Last week I’ve released a
test version
for the upcoming 0.9.15 release of PulseAudio. It’s going to be a major one,
so here’s a little overview what’s new from the user’s perspective.

Flat Volumes

Based on code originally contributed by Marc-André Lureau we now
support Flat Volumes. The idea behind flat volumes has been
inspired by how Windows Vista handles volume control: instead of
maintaining one volume control per application stream plus one device
volume we instead fix the device volume automatically to the “loudest”
application stream volume. Sounds confusing? Actually it’s right the contrary, it feels pretty natural and
easy to use and brings us a big step forward to reduce a bit the
number of volume sliders in the entire audio pipeline from the application to what you hear.

The flat volumes logic only applies to devices where we know the
actual multiplication factor of the hardware volume slider. That’s
most devices supported by the ALSA kernel drivers except for a few
older devices and some cheap USB hardware that exports invalid
dB information.

On-the-fly Reconfiguration of Devices (aka “S/PDIF Support”)

PulseAudio will now automatically probe all possible combinations
of configurations how to use your sound card for playback and
capturing and then allow on-the-fly switching of the
configuration. What does that mean? Basically you may now switch
beetween “Analog Stereo”, “Digital S/PDIF Stereo”, “Analog Surround
5.1” (… and so on) on-the-fly without having to reconfigure PA on
the configuration file level or even having to stop your streams. This
fixes a couple of issues PA had previously, including proper SPDIF
support, and per-device configuration of the channel map of

Unfortunately there is no UI for this yet, and hence you need to
use pactl/pacmd on the command line to switch between the
profiles. Typing list-cards in pacmd will tell you
which profiles your card supports.

In a later PA version this functionality will be extended to also
allow input connector switching (i.e. microphone vs. line-in) and
output connector switching (i.e. internal speakers vs. line-out)

Native support for 24bit samples

PA now supports 24bit packed samples as well as 24bit stored in
the LSBs of 32bit integers natively. Previously these formats were
always converted into 32bit MSB samples.

Airport Express Support

Colin Guthrie contributed native Airport Express support. This will
make the RAOP
audio output of ApEx routers appear like local sound devices
(unfortunately sound devices with a very long latency), i.e. any
application connecting to PulseAudio can output audio to ApEx devices
in a similar way to how iTunes can do it on MacOSX.

Before you ask: it is unlikely that we will ever make PulseAudio be
able to act as an ApEx compatible device that takes connections from
iTunes (i.e. becoming a RAOP server instead of just an RAOP client).
Apple has an unfriendly attitude of dongling their devices to their
applications: normally iTunes has to cryptographically authenticate
itself to the device and the device to iTunes. iTunes’ key has been
recovered by the infamous Jon Lech
, but the device key is still unknown. Without that key it
is not realistically possible to disguise PA as an ApEx.

Other stuff

There have been some extensive changes to natively support
Bluetooth audio devices well by directly accessing BlueZ. This code
was originally contributed by the GSoC student João Paulo Rechi
Vita. Initially, 0.9.15 was intended to become the version were BT audio
just works. Unfortunately the kernel is not really up to that yet, and
I am not sure everything will be in place so that 0.9.15 will ship
with well working BT support.

There have been a lot of internal changes and API additions. Most of
these however are not visible to the user.