[alsa-devel] Looking for ideas to solve ruby alsa duplex problem

Alban Peignier alban at tryphon.eu
Sat Oct 30 12:19:33 CEST 2010

Hi alsa guys,

We're working on a ruby binding for alsa :
http://projects.tryphon.eu/ruby-alsa/. PCM Playback and Capture are
supported for a long time (and used in production for several months).
Ruby developers can find the gem on http://rubygems.org/gems/ruby-alsa.

But we're trying to investigate a problem with "duplex mode" :
http://projects.tryphon.eu/ruby-alsa/ticket/4. We can't find a way to
record and playback simple stereo streams in the same process without
dummy hackings :-/ We don't need an extreme latency, just a simple
process to add/receive streams on network (our LinkStream/LinkBox project).

I hopes it's only a misusage of the ALSA API or a mistake in
hardware/software configurations. But after several weeks on this
problem, we need fresh ideas :)

Even if you have no idea about ruby, the Playback [0] and Capture [1]
are very simple wrappers around the native ALSA API [2] (mapped with
ruby ffi [3]). The alsa device is opened and configured using a shared
open method in Stream [4]. Very few code in fact.

I hope an expert eye will find a beginning of solution ;)

Kind regards,

0. http://projects.tryphon.eu/ruby-alsa/browser/lib/alsa/pcm/playback.rb
1. http://projects.tryphon.eu/ruby-alsa/browser/lib/alsa/pcm/capture.rb
2. http://projects.tryphon.eu/ruby-alsa/browser/lib/alsa/pcm/native.rb
3. http://github.com/ffi/ffi
4. http://projects.tryphon.eu/ruby-alsa/browser/lib/alsa/pcm/stream.rb

Alban Peignier - alban at tryphon.eu

Tryphon : Radio, Web and Free Software

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