Subject: Re: Re: [linux-audio-dev] Oss & threading -- is it possible
From: hexe_2003_AT_directbox.com
Date: Fri Oct 10 2003 - 18:41:39 EEST
-------- directBOX Reply ---------------
From: paul_AT_linuxaudiosystems.com
To : linux-audio-dev_AT_music.columbia.edu
Date: 10.10.2003 17:37:43
>Hello !
>
>I've read somewhere that it is not possible that threads write different data to /
>dev/dsp.
>But how does Cheesetracker, for example, make it then?
i don't how cheesetracker does it, but it requires user-space
synchronization (e.g. pthread_mutex_(un)lock). with ALSA, you don't
need to to do this - any thread can write to the device at any
time. that's the theory, at least. in general, its probably a bad
design to be doing that, much like it is for GUI programming, where
its better to have a single thread mediate between the "device" and
the rest of the program.
------------------
But well, If I synthize ( ? spelling) two signals and want to send them at the same time
to the device, my first idea'd be:
1.) Open /dev/dsp, maybe O_NONBLOCK | O_WRONLY
2.) thread
3.) two threads calculate the both signals
4.) sync them
5.) two threads write their signals to /dev/dsp
6.) threads close
certainly some of this. I mean mp3blaster, for example, have several pids while playing audio streams, and it is basicly OSS-programming and not alsa.
Am I so wrong ? ;)
Sascha Retzki
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