Re: Sound Events and The Enlightened Sound Daemon

[Caolan McNamara <Caolan McNamara ul ie>]

On 05-May-98 Riku Voipio wrote:
>On Tue, May 05, 1998 at 05:39:26PM +0300, Ville Hautamaki wrote:
>
>> I am _not_ trying to start a serious flame war in here, but our 
>> (Adam and me ) gnome sound proposal follows (Adam correct me if I am wrong):
> 
>>      -Base API to NAS which has been here for years. And also it has 
>>      sopport in some app's (like mpg123) 
>>      -NAS is network transparent which is added plus.
>
>...But last time I tested nas it decided to own my soundcard.
>It's very bad that you can't use any other than nas-aware apps
>after loading NAS.

thats just the way the sound driver is written, theres no way around that
really. if nas was to just open /dev/audio when it had a request and close
it when all conections had closed it would alleviate the matter, but not
solve it. you cant have two apps using /dev/audio together, *unless* they
both communicate with a server that sits on /dev/audio and mixes the streams
which is what nas does. some hairly solutions would be
1) have a /dev/audio driver that allows multiple processes to use it, and mixes
the streams itself, i.e move the nas mixing code into the driver, i made a start
at this. i didnt do too good a job at it though :-), and my attempt is crud.
2) some kind of LD_PRELOAD lib that intercepts open requests to /dev/audio et al
and fakes up a call to nas, so that legacy apps can interwork with nas. 
unfortunately the apps that use /dev/audio tend to be stuff like quake that
memmap /dev/audio and do all sorts of tricks with it, i havent been able to 
think of an easy way around this one, but i like it better as a solution, 
utterly hackky as it is.

the bottom line is that it doesnt matter what sound server you use, under linux
only one app at a time can have /dev/audio open for reading, one can have it
open for writing, (making 2) or one can have it open for read/write. nas just
highlights this limitation by opening /dev/audio for rw on startup and only
releasing /dev/audio on closedown. 

we're in the darkages of audio, in the land where graphics once were, many os's
only allow one process to use the resource.

C.

Real Life: Caolan McNamara           *  Doing: MSc in HCI
Work: Caolan.McNamara@ul.ie          *  Phone: +353-61-202699
URL: http://skynet.csn.ul.ie/~caolan *  Sig: an oblique strategy
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