Time delay in setting property & audio mixer element

[Pietro Battiston]

Hello,

if you

git clone git://pietrobattiston.it/fingerpicking -b minimal
cd fingerpicking
python finger.py


and then try to move the mouse over the empty area, you will hear that
the pitch changes along with the horizontal position of the cursor. And
that's precisely what I desired.
What is unintented is that it does so with approximately 30 ms. of
delay. And I'm not able to clearly understand the cause.

The wave is provided by an "audiotestsrc" element. Every time the
pointer moves, its "freq" property is changed. So:
1) is the audiotestsrc element intrinsecally too slow in changing
frequency? or,
2) is the audiotestsrc element asked to change frequency only when the
next main loop is ran? or,
3) is there an audio buffer somewhere "after" gstreamer?
4) am I missing something else (in the end, it's been few days since I
first programmed with gstreamer)?

I would tend to exclude the third, because I notice no delay in the act
of pressing - releasing the mouse.
The second looks reasonable to me: if that's the problem, is there any
solution?
Or more in general: do you suggest that gstreamer can do what I want or
am I using the wrong tool?



While I'm at it, another question: I searched for some element doing the
inverse of "tee" for audio. I found a discussion on the argument:
http://gstreamer-devel.966125.n4.nabble.com/aggregator-element-td973247.html
which however was dropped. Dan:
http://gstreamer-devel.966125.n4.nabble.com/aggregator-element-td973247.html#a973254
proposed several "interpretations" of that request, and what I need is
precisely the last: "For audio-only mix the inputs to one output, like a
multi-track studio mixer? ". Is there such an element?

Thanks to all in advance

Pietro