DIrectSound on top of openAL ?

[Darragh Bailey]

Actually just spotted that some of the features are approved on the wish
list, so it seems that OpenAL will include them in it's next
specification.


On Thu, Oct 30, 2008 at 10:46:51AM +0000, Darragh Bailey wrote:
> On Tue, Oct 28, 2008 at 02:16:12PM -0700, Chris Robinson wrote:
> > The biggest problem is updating the sound buffer in real-time (DSound lets you 
> > lock a sound buffer and modify it while it's playing; OpenAL only lets you 
> > rebuffer the whole buffer, while it's not attached to any source). I get 
> > around this by spawning a real-time thread which queues small chunks "just in 
> > time" to keep the buffer playing, but this is a hack at best.. there's no way 
> > to know how much you need to buffer ahead so OpenAL doesn't run out during an 
> > update, some apps are more sensitive to a large write-ahead, and real-time 
> > threads aren't really available in Wine (meaning even larger sections would 
> > need to be queued to be able to update in time). The problem is compounded 
> > when you consider multiple DSound buffers can share the same data buffer.

Couldn't tell if this is on the wish list, there appears to be some
suggested enhancements for better buffer control, but I don't know
enough to determine whether they actually match up.

> > Another problem is the lack of panning. OpenAL has no controls for panning a 
> > 2D sound. At most you can move the sound left and right to simulate panning 
> > (for mono sources; stereo is out of luck), but the actual algorithms are 
> > implementation dependant and thus would not produce consistant results.

Requested:
Item:2D panning/speaker level support
Contributor: Creative
Description:
Approval Status: Approved

> > Additionally, OpenAL hides a lot of the hardware vs. software caps. OpenAL 
> > doesn't tell you if you're using hardware or software, while DSound would 
> > tell you. Of course you can always lie and say you have hardware (which I 
> > found was needed to get some games to even attempt to use DSound3D), but it's 
> > not entirely proper.

Looks like this has been requested too:
Item: Generic Effects		
Contributor: Creative 
Description: OpenAL could have a generic mechanism for enumerating and making use of
the effects capabilities of the active audio device. 
Approval Status: Approved

> 1.0 was released 2000, 1.1 in 2005, so it's probably due a new release
> in the next year/two, so it might be possible to add some feature
> requests that would make implementing DirectSound on top of OpenAL
> visible in the future.

If all of the wish list gets added, it would appear the next
specification of OpenAL would appear to me to go a long way to allowing
wine to implement the Windows sound API's via that, rather than having
to support various drivers.

-- 
Darragh

"Nothing is foolproof to a sufficiently talented fool."