Full duplex ALSA-plugin

[Christian Gruber <christian.gruber@voiceinterconnect.de>]

I was looking for information on writing an echo cancellation ALSA-plugin. So I studied 
the ALSA-plugin docs and also found several interesting threads in this mailing list. But 
what I found out, was quiet disillusioning.

If I understood the ALSA-plugin concept right, there is no possibility to write a plugin 
working on two streams, a playback and a record stream, simultaneously. One can only write 
a filter plugin, which works either on a playback stream or a record stream but not both. 
And there is no possibility to open a full duplex stream (consisting of playback and 
record) with snd_pcm_open().

Is there a reason, why full duplex streams are not implemented yet? Or is it planned in 
the future to implement this feature?

Regards,
Christian