[pulseaudio-discuss] java sound implementation using pulseaudio - ports

[Colin Guthrie]

Ioana Ivan wrote:
> Hi,
> 
> We've been trying to write an implementation of 
> javax.sound.sampled.Mixer(and the associated classes: SourceDataLine, 
> TargetDataLine, Clip, and Port) that uses pulseaudio as a backend. So 
> far, SourceDataLine, TargetDataLine and Clip are working (somewhat, 
> there are still issues that need to be fixed), but we're not sure how to 
> approach Port.
> 
>  From the java API:
> "Ports are simple lines for input or output of audio to or from audio 
> devices. Common examples of ports that act as source lines (mixer 
> inputs) include the microphone, line input, and CD-ROM drive. Ports that 
> act as target lines (mixer outputs) include the speaker, headphone, and 
> line output. You can access port using a Port.Info  object."
> 
> Ports should have an open() and close() method, and ideally they should 
> also support volume and mute controls. There currently is an 
> implementation of Port in openjdk that uses alsa to enumerate the 
> devices that could connect to the sound system, and implement the 
> required methods.
> 
> We were wondering whether there's anything in the pulseaudio API that 
> could be used to do something similar, and, if not, how problematic 
> using the old version of Port(that uses alsa directly) with our mixer 
> that uses pulseaudio is.

I spoke to you on the mailing list but this is a little clearer I think.

Basically you just want to expose the volume of the various Sinks and 
Sources here. I would just get a list of all the Sinks and provide 
playback Ports that allow volume control and muting etc. and do a 
similar exposure for the Sources.

I'd use the introspection stuff to do this (tho' not overly sure).

http://0pointer.de/lennart/projects/pulseaudio/doxygen/introspect_8h.html

You can probably use the source of pavucontrol to work out what to do here.

You can of course export a volume on a "per stream" basis, but I'd 
imagine this doesn't map too well to the Java API seeing as streams will 
come and go quickly but sinks/sources will be slightly more long term 
(tho can still come and go (e.g. when a usb audio device is plugged in 
or a network sink is detected etc.)


I think whatever is in the "Output devices" and "Input devices" tab in 
pavucontrol (from git) is probably what you want...


HTHs

Col

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Colin Guthrie
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http://colin.guthr.ie/

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