[Openal-devel] GStreamer OpenAL sink

[Chris Robinson]

Here's a preview of the OpenAL sink I've been working on for GStreamer.

http://kcat.strangesoft.net/gst-openal.tar.bz2

And a small example app:

http://kcat.strangesoft.net/gst-openal.cpp

The sink allows you to specify a device/context/source to play with, or to 
retrieve the same, allowing for some manipulation by the app (eg. play a 
background music track with GStreamer and control its volume using the source 
gain, or play a lengthy mono track and place it in 3D space like any other 
source). The stream will play asynchronously, and it will work with any 
GStreamer-supported format.

It even stays synced to a video stream.. imagine using a glvideo sink to paste 
video onto a texture in the game world, along with an alaudio sink to play the 
corresponding audio (remember those video screens in Doom 3?). And it all 
happens automagically. Of course, even without going all extravagant like 
that, it's an easy way to play a prerendered cut-scene, opening video logo(s), 
or a simple music track on the same audio device as the app.

The sink supports the float32 and double extensions, as well as mcformats, 
mulaw, and mulaw-mcformats, with proper checks.

Currently the sink requires OpenAL Soft 1.12, since it's the only 
implementation to support ALC_EXT_thread_local_context which is needed for 
context safety across threads. It should Just Work with any other 
implementation that adds support for it, however.

I can try to relax that requirement when the sink is given a custom context, 
though it will require the context to remain set and no errors generated with 
it while the stream is playing.

Building the sink requires an alext.h header that defines the appropriate 
extension tokens and types. It also (obviously) requires the gstreamer 
development packages. You may likely need to pass --prefix=/usr to configure, 
too (that's the default prefix for GStreamer installed by package managers, 
and it doesn't seem to find plugins installed in the /usr/local prefix).


Assuming it works out well enough for you guys, I'll probably give it over to 
the GStreamer devs to see if it can be included in the official packages.