[alsa-devel] performance between access mothods!

[Takashi Iwai]

At Sun, 05 Jul 2009 09:03:23 -0300,
Guilherme Longo wrote:
> 
> Hi all!
> 
> I came across a doubt regarding the the access mode between application 
> and PCM device.
> It is a hardware parameter related property and there are 5 different 
> types available:
> 
> SND_PCM_ACCESS_MMAP_INTERLEAVED
> SND_PCM_ACCESS_MMAP_NONINTERLEAVED
> SND_PCM_ACCESS_MMAP_COMPLEX
> SND_PCM_ACCESS_RW_INTERLEAVED
> SND_PCM_ACCESS_RW_NONINTERLEAVED
> 
> taking in account that these first 3 parameters has direct communication 
> with the memory, that means a higher speed operation?

Yes.  The others are using copy_from/to_user(), so there are slight
overheads by explicit copying.


> And the fact of 
> the interleaved has all the samples mixed together , makes any 
> difference in performance in comparison to the noninterleaved that has 
> samples stored on different buffers?

No.  It's just a difference of what format the hardware supports.


Takashi