[LAD] Routing signals in mixer (Ardour, Qtractor)

[Rui Nuno Capela]

On 07/12/2010 09:47 PM, fons at kokkinizita.net wrote:
> On Mon, Jul 12, 2010 at 09:30:05PM +0100, Rui Nuno Capela wrote:
> 
>> problem is that input buffers are always read before any output signal
>> is produced, while on the same process period cycle. iow, you're
>> consuming what hasn't been produced yet. that's why you'll probably get
>> silence, at best.
> 
> This should still work, you should get the output from the
> previous cycle. Unless
> 
> 1. you clear outputs before reading inputs, and
> 2. Jack is using the same buffer for the feedback input
> and the output that connects to it.
> 

yep, all outputs are zeroed at each cycle. i suspect some potential
garbage could be injected in the process otherwise...


> (2) is an Jack bug wich I reported at least a year ago.
> Don't know if it has been fixed. You can work around it
> by connecting a second (silent) output to the feedback
> input - this stops Jack sharing the buffer. Or insert
> a dummy client as you suggested.
> 

i think that's the "zero-copy" optimization that jack pursues when ports
are single connected?

byee
-- 
rncbc aka Rui Nuno Capela
rncbc at rncbc.org