[pulseaudio-discuss] Monitor devices and unconnected sources.

Knut-Håvard Aksnes kna at tirsdagsklubben.nu
Fri Oct 24 03:39:18 PDT 2008

I am working on an application where I listen to monitor interfaces. The 
audio stream is intended to be merged with other AV streams later down 
the processing pipeline using third party code, (open source but quite 
complex to understand and modify). My problem is that the application 
connecting to the pulse audio monitor might or might not send audio, 
depending on user input, if it doesn't send audio it won't connect to 
the pulse audio source, the application might also disconnect the audio 
based on user input, before terminating itself. (Audio is handled by 
plugins that might get loaded and unloaded based on user input)

My problem is that I really need to receive silence (zero filled audio ) 
instead of empty packages from the monitor interface when no sources is 
connected. Is it possible to configure pulse audio to give me this?

The problem of implementing this myself in client code is to avoid 
timing problems  when the client connects or disconnects at a later 
stage. I need to do do non-blocking calls to the API and could easily 
get into problems in differentiating between jitter and the situation 
where no client are connected, but need to treat the two situations 
differently. I might be able to handle part of it using 
pa_stream_set_underflow_callback and pa_stream_set_started_callback but 
I miss something like pa_stream_set_stopped_callback with a callback for 
use on monitor interfaces when the last application connected to a sink 
terminate the connection.

If this is done using suspend/resume for monitor interfaces this should 
be mentioned in the programmer API.
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