Re: [RFC][PATCH] Transparent network support through polypaudio

[Pierre Ossman <ossman@cendio.se>]

Clemens Ladisch wrote:
> Pierre Ossman wrote:
> 
>>I've implemented an ALSA plugin that allows any well-behaved ALSA 
>>application transparently use the Polypaudio network protocol.
>>
>>It is my desire to have this included in ALSA (-lib preferably) so that 
>>it will be included in most dists.
> 
> 
> It's dependent on polypaudio, so it should better go into the
> alsa-plugins package.
> 

I suppose. Then it's just the matter of getting that packaged into the 
dists (fedora doesn't).

> 
>>Since some applications do not use these in a sane manner
> 
> 
> Nothing in the ALSA API requires applications to use poll() (or to use
> blocking writes).
> 
> 
>>(I'm looking at you mplayer)
> 
> 
> And you're speaking with mplayer's ALSA driver maintainer.
> Is there anything wrong with mplayer?  ;-)
> 

Technically no. It's just that it does things in way that makes my life 
more difficult. :)

Btw, mplayer seems to call snd_pcm_prepare() twice. Not sure if that's 
valid behaviour.

> 
>>the mainloop abstraction is also run on most of the ALSA plugin
>>callbacks.
> 
> 
> When an applicatioh disables the stop_threshold, the device is supposed
> to continue playing with the current buffer contents (which _is_ a
> rather extreme case).
> 

The ring buffer design is very difficult to emulate when you have a 
simple queue. Since few (if any) application will rely on this 
behaviour, I've decided to ignore it for now.

> I think you may be required to use a timer for the mainloop.  What does
> polypaudio actually do in this callback?  How often must it be called?
> 

Primarily updates to available buffer space on the server. As for how 
often, I don't really know. Once every period would be a safe guess.

A timer wouldn't be that easy to implement. I want to avoid putting more 
stuff in another thread since the current solution allows me to avoid locks.

Rgds
-- 
Pierre Ossman                Telephone: +46-13-21 46 00
Cendio AB                    Web: http://www.cendio.com


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