IcedTea-Sound 1.0.0 Released!

[Omair Majid]

* Guillaume Alaux <guillaume at alaux.net> [2014-07-30 08:01]:
> So if I understand correctly, icedtea-sound is available – for
> instance – to applications that would explicitly want to use
> Pulseaudio (or, in the future, any other sound provider à la
> Pulseaudio).

Yes.

> I am still a bit puzzled by why OpenJDK does not use it (totally naïve
> question here)? Is it because it would create a dependency on
> pulseaudio rather than Alsa? Or maybe there is already a way to make
> OpenJDK+IcedTea use IcedTea-Sound?

I think the biggest reason OpenJDK does not use it is that it's not
really needed, even in distributions that fully support PulseAudio.

The PulseAudio devs implemented a clever thing, you see. The included
support for hooking the ALSA userspace API back into PulseAudio. So, in
a distribution that supports PulseAudio, things are set up so data flows
in the following way (this is a simplified diagram):

OpenJDK -> ALSA userspace API -> PulseAudio daemon -> ALSA kernel API

So, OpenJDK (or IcedTea or really any program) that uses the ALSA
userspace API can continue using that and (almost transparently) get
full support for PulseAudio and all the features that provides, without
needing to have any special code to support PulseAudio explicitly.

What IcedTea-Sound does is to provide another audio provider in
OpenJDK/IcedTea that does this instead:

OpenJDK -> PulseAudio API -> PulseAudio daemon -> ALSA kernel API

This is basically using the PulseAudio-specific API to do something in a
PulseAudio-specific way. Theoretically, it can probably be more
efficient as well as provide features that are simply not available
using the ALSA userspace API (like using the API to play a sound on a
remote machine over the network). But for most OpenJDK/IcedTea users,
this is not really needed.

So, why did we write this code? At the time we started working on this
OpenJDK wouldn't use PulseAudio, due to a few bugs/quirks about how it
used the ALSA API, like [1]. This was identified much later; once those
were fixed, OpenJDK worked (more or less) without any issues with
PulseAudio. 

Hope that clears things up.

Cheers,
Omair

[1] https://bugs.openjdk.java.net/browse/JDK-6832063

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