[LAD] [Jack-Devel] jack2's dbus name

Jussi Laako jussi at sonarnerd.net
Thu Jun 18 20:27:55 UTC 2009


Lennart Poettering wrote:
> If an application can send PA data in larger blocks then we are happy
> about it and take it. Of course, if the application needs low
> latencies then it shouldn't pass huge blocks to us, but instead many

No, generally data needs to be fed _to_ application immediately when it
becomes available after A/D conversion (PCI DMA completion interrupt).
Application(s) process the data and it is ought to go to D/A conversion
on next hardware interrupt (PCI DMA reprogram interrupt), along with
time-synchronous data from other applications. This creates total
latency of inputhw+blocksize+outputhw. Generally input and output
latencies should be around few tens of samples (due to delta-sigma
converter resampling filters etc). And generally blocksize is also kept
around 64 or so.

> The big difference between JACK and PA here is that in JACK the
> transfer of data is mostly done synchronously while in PA we do that
> asynchronously. Which is the case because we need to make sure that no

Yes, and this is because all applications are ought to work in harmony
as a whole construct, just like a symphony orchestra, following the pace
set by conductor.


	- Jussi



More information about the Linux-audio-dev mailing list