19.11.2015 21:47, Alexander E. Patrakov wrote:
19.11.2015 11:48, Georg Chini wrote:
On 19.11.2015 05:08, Alexander E. Patrakov wrote:
19.11.2015 00:43, Georg Chini wrote:
On 15.11.2015 22:08, Alexander E. Patrakov wrote:
However, I'd argue that this phase metric can be improved without the
deadband and beyond what this deadband-based implementation provides.
What is the problem with the dead band? There are physical limitations
to what makes
sense to correct and the dead band just takes care of those limits.
There are no such limits once you (or your second-order filter) start
averaging previous latency difference measurements.
You are definitely wrong there. This would only be (nearly) true, if the
error of the latency
measurement would be small. In practice it isn't and even the best low
pass filter
will not remove all of the error. Take a look at the latency error
values that my
code provides. It already is a low pass filtered value.
I can, so far, only make a conclusion that I should try a different
lowpass filter.
Especially in the first couple of seconds you do not get very reliable
values. There
must be something in pulseaudio which is preventing that. Maybe it is
the time
smoother that has to settle down. I think you can also see this effect
in the images
of the original recording - the phase is drifting during the first 50
seconds and
then it is nearly constant.
The phase is drifting because the original latency is too far from the
desired one. Nonzero latency difference => nonzero rate adjustment as
compared to the ideal value => phase drift. Or, as phase is directly
proportional to the latency, it's just the "correction of the big
initial latency difference" process. So, my plots indeed show how fast
or how slow the rate controller deals with such bad initial conditions.
Well, after a second look at the plots, I do notice something unusual.
On the plots where I started the sine wave shortly after loading the
module (instead of waiting), it can be seen that the initial phase is
suspiciously close to zero, while my scripts set it to zero at the end.
So the whole peak looks unnecessary (as if there is some "garbage in"
coming from other parts of PulseAudio when estimating the latency).
--
Alexander E. Patrakov
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