[alsa-devel] [PLUGINS] Multichannel over I2S : extra cost of user space plugins
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
Matt Flax wrote:
Recently I was advised to channel multichannel audio over stereo I2S
Why would you want to do that? Don't you have the appropriate number of I²S lines?
and unpack in user space with plugins.
Why?
Right now, with a hacked machine driver, I get DMA unpacking to multichannel for free.
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 ?
Plugins can query what the actual sample format is (and can constrain them to what they support).
Regarding the actual channel unpacking, will it cost a lot more to do this in user space, rather then using the DMA silicon ?
Of course.
Regards, Clemens
participants (2)
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Clemens Ladisch -
Matt Flax