share/smix pcm plugin [was [linux-audio-dev] Audio routing issues for linux..]

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Subject: share/smix pcm plugin [was [linux-audio-dev] Audio routing issues for linux..]
From: Joern Nettingsmeier (nettings_AT_folkwang-hochschule.de)
Date: Mon Jun 10 2002 - 18:31:22 EEST


hi !

in reply to a posting by juan linietsky, Paul Davis wrote:
>
[allowing multiple apps to play at the same time (esound-style) on
hardware that does not support multi-open]
>
> * ALSA already has the "share" PCM device type which allows
> multiple access to the same underlying hardware. It hasn't
> been tested very much, but it does basically work.

i think it does not do this. from the docs:

This plugin allows sharing of multiple channels with more clients.
The access to each channel is exlusive (samples are not mixed together).
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
It means, if the channel zero is used with first client, the channel
cannot be used with second one.
If you are looking for a mixing plugin, use the smix plugin *unknown
reference!* .
                                                           
^^^^^^^^^^^^^^^^^^^^
it seems the share device as many people need it is not yet implemented.
i don't know how hard this is or what the problems are. alsa gurus ?

***

side question: if the alsa-lib provided "software multi-open" and
software mixing as a plugin that uses the hw: pcm device for output
(i.e. without further processing), would that increase latency compared
to direct hw: access ?

regards,

jörn


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