[alsa-devel] [PLUGINS] Multichannel over I2S : extra cost of user space plugins

[Matt Flax]

Recently I was advised to channel multichannel audio over stereo I2S and 
unpack in user space with plugins.

I have questions about this approach.

Right now, with a hacked machine driver, I get DMA unpacking to 
multichannel for free. It works with all sample rates in silicon and it 
also works with all word sizes.

If I switch to user space ALSA plugin unpacking, as advised, can anyone 
answer the following questions please :

If I want to handle all word sizes which are currently implemented S16 
-> S32, do I need to use different plugins to handle different word sizes ?

Regarding the actual channel unpacking, will it cost a lot more to do 
this in user space, rather then using the DMA silicon ? The bcm2835 is 
not a very powerful processor and this is a concern.

Does anyone have an example plugin which will handle all word sizes 
through one plugin device ?


thanks

Matt