Multiple consumers of /dev/dsp

David Adam zanchey at
Thu Jul 21 13:55:33 GMT 2005


On Thu, 21 Jul 2005, Josef Karthauser wrote:

> In the past I'm sure that we supported the mixing of audio in the kernel
> so that multiple applications could open /dev/dsp at the same time.  Was
> this a function of the audio card driver, or of the audio subsystem?
> Currently on my new machine I don't get any mixing, and applications
> fail to open /dev/dsp if it's already open by something.
> The current hardware is:
>     FreeBSD Audio Driver (newpcm)
>     Installed devices:
>     pcm0: <Intel ICH4 (82801DB)> at io 0xee00, 0xe000 irq 9 bufsz 16384 kld
>     snd_ich (1p/1r/0v channels duplex default)
> Am I imagining that this use to the case or isn't it enabled by default?

It's not on by default, AFAIK, but setting a couple of sysctls will allow
you to have more than one program playing sound at once.

# sysctl hw.snd.pcm0.vchans=4
# sysctl hw.snd.maxautovchans=4

Check out
(the section titled 'Utilizing Multiple Sound Sources').


David Adam
zanchey at

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