Re: [Ekiga-list] A comparison ALSA-PULSE (long, addendum)

[Alec Leamas <leamas alec gmail com>]

Derek Smithies wrote:
> Hi,
> > > Perhaps it's PTLib underneath it? I really don't know, I'm just 
> > > throwing
> > > the idea out there!
>
>  It is PTLib which contains the code to read from alsa.
>
> Surely, the ideal is not to go via ALSA, but have ptlib directly talk 
> to pulse. Thus, we need to write a ptlib plugin for pulse audio.
>
> We know how ptlib plugins work. There are example plugins for alsa, 
> esd, oss, sunaudio. The big question is writing a plugin for pulse.
>
> What is involved in writing code that talks directly to pulse ?
> Anyone know example code, or of the pulse api docs?
>
> Please don't refer me to docs which say "just use alsa code". We are 
> using alsa code, and that is why we are having this issue.
>
> Derek.
I think you are right. For the reasons you mention, but also because the 
current alsa plugin is seriously flawed  I made a short review very 
late  yesterday. Among other things it's synchronized in a way that 
forces playback and record to wait for each others' I/O operations(!)

With this said, I don't (yet) see any problems in understanding and 
using the external interface. These problems are within the alsa plugin.

So: with limited resources we have a choice to either "fix" (i. e., 
major rewrite of) current alsa plugin, or make a pulse plugin. The 
latter is most likely easier. But then we leave platforms without pulse 
in the dark ages. So question is: do we need a working alsa plugin if we 
have a pulse one? Anyone?  (let's take silence as a "no"  :-) )

What disturbs me a little is the way the plugin interface "seems" to 
be,  at least from the alsa example. Question is if there is a way to 
arrange event-driven  I/O  - current code is strictly polled. OTOH, we 
can live with that, for sure. But there "might* be other hooks in the 
plugin interface not used  today... we  might need to backwards-engineer 
some docs... possibly expanding the plugin interface in a 
backwards-compatible way....

There is good pulse doc's on their website e. g., 
http://0pointer.de/lennart/projects/pulseaudio/doxygen/