[music-dsp] who else needs a fractional delay.

Bogac Topaktas bogac at bteaudio.com
Sat Nov 20 17:39:24 EST 2010


>Ross Bencina wrote:
> From my point of view the more difficult thing is recovering a stable
> wordclock from a jittery packet stream -- and getting this to start up
> quickly enough to be useful. In the past I've used an Ordinary Least
> Squares
> regression on packet timestamps to estimate the incoming sample rate and
> intercept (time offset). This time I have a mechanism for time offset
> based
> on the assumption that the "most on time" packets represent the best time
> offset, but the rate estimator is still a bit of a mystery... I have a
> Kalman filter version that works about as well as the OLS rate detector
> and
> is a little cheaper -- lately I've been reading up on "robust regression"
> methods (LMS and TLS) -- they're pretty costly but I'm hoping they'll
> allow
> me to lock on to the word clock more quickly.
>
> I hope that's clear. Suggestions on techniques or methods I havn't already
> mentioned would be most appreciated...

I think what you need is a robust state estimator, for instance a
H-infinity filter. Check out estimation theory literature for more info;
Dan Simon's book is a good resource:

"Optimal State Estimation: Kalman, H Infinity, and Nonlinear Approaches"
ISBN-10: 0471708585






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