Re: Ibm ViaVoice.

[Dave Mielke <dave mielke cc>]

[quoted lines by Alessandro Rubini on December 8, 1999, at 17:20]

>/dev/audio is a single-open device, so any program that keeps it open
>prevents other programs to use it. I personally see no valid reasons
>why /dev/audio (or any device, in general) should be single-open, but
>not every developer agrees with me (think, for example, of two
>programs playing audio at the same time).

It's not quite that simple. For multiple open-for-writes, you'd need to add
code into the kernel to add all of the concurrent audio streams together before
feeding them to the digital-to-analog converter on the sound card. Foir
multiple open-for-reads, you'd need to support multiple parallel
kernel-resident buffers, which means, among other things, that you could no
longer copy straight from the DMA channel to the application's memory.

The good news is that one form of multiple concurrent audio device open, i.e.
one for writing and one for reading, is supported. You'd need this, for
example, to play and record at the same time, or to use a full duplex internet
phone service. The only Linux sound drivers which I know of which do support
this type of operation are those provided by ALSA.

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