Hi Philip,

That's a good question. I don't know if OpenAL supports customn DSP
effects or not, but I can check. In any case that would only be half
the problem here.
I'm currently  using a cross-platform audio library called sfml-audio
which is basically a nice front-end for OpenAL. The SFML developer has
added all the necessary code to load wav files, ogg files, and various
other file types and then loads them into OpenAL's sound buffers for
playback and positioning. Plus has added support for streaming and
that sort of thing. In other words it is basically the open source
equal to your PB Streemway library minus the sound encryption and it
uses OpenAL rather than DirectSound. So if sfml-audio doesn't support
custom DSP but OpenAL does then it would be up to me to reinvent the
wheel by creating my own Streemway or sfml-audio type front-end to get
a simple stereo pan effect. Definitely not a very happy thought seeing
as such a project would take a good month to create if not longer.

As for justifying a cross-platform engine what can I say? In my
opinion the fact that my wife and I have chosen to go Linux but most
of my customers still use Windows is justification enough. Its like
what would be the point spending months, even years, creating games
that would only run on Windows when three out of four computers my
wife and I own now all run Linux.

The only reason we have kept that one Windows system around is because
we own some expensive software that we can still use like Soundforge,
Visual Studio Pro, as well as various games that won't run on Linux
and still is of personal use to us.  As good as Linux is admitedly
there are certainly apps you can't find for Linux such as the Halmark
software for creating personalized holiday gift cards that my wife
likes to use. for that we can justify keeping one Windows system
around, but not maintaining three or four computers with Windows
software on it. That obviously gets expensive. Especially in light of
the fact more and more developers are going the route of Microsoft and
licensing software for a single computer.

So I have elected to take whatever time and energy is necessary to
modify my Genesis Engine, which was written in C++ anyway, to use
non-proprietary APIs like SFML so I could build high quality Linux
games for myself while still being able to sell to a mostly Windows
market. It is buggy right now, but I'm sure I'll eventually get it all
working in time.


On 10/5/10, Philip Bennefall <phi...@blastbay.com> wrote:
> Hi Thomas,
> Here's a quick thought for you to ponder. Does OpenAl have support for
> custom dsp? A callback interface or similar for each sound that enables you
> to add your own dsp effects or filters to the audio in real-time? If so, you
> could write a pan effect and simply layer it on top of the sound system and
> you'd get a perfect pan effect just like in DirectSound, without having to
> modify the libraries in the slightest. The actual panning, as you know, is
> trivial math; the only concern is whether you can get at the raw audio data
> as it is being played, and whether you can do so not only staticly but also
> in real-time in order to make rapid/dynamic changes. XAudio2 supports this,
> and so this is what I plan to do for Streemway if the XAudio2 3d renderer
> turns out to be unable to reproduce panning accurately which seems to be the
> case with OpenAl.
> I think the idea of a cross platform game engine is great, if you can
> justify the extra time spent etc. Good luck!
> Kind regards,
> Philip Bennefall

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