From: Greg Berchin on
On Sat, 03 Jul 2010 06:48:57 -0400, Greg Berchin <gberchin(a)comicast.net.invalid>
wrote:

>Possibly useful: see US Patent 5375067 for a discussion of Central Time and RMS
>Delay.

I gotta stop typing before my brain is awake.

Make that Central Time and RMS *Duration*.
From: robert bristow-johnson on
On Jul 3, 6:48 am, Greg Berchin <gberc...(a)comicast.net.invalid> wrote:
> On Fri, 2 Jul 2010 20:37:14 -0700 (PDT), robert bristow-johnson
>
> <r...(a)audioimagination.com> wrote:
> >> ... but Steve and I were talking about RMS delay spread.
>
> >"spread" from what?  zero?  or some mean delay?  how is the mean
> >defined?
>
> >"RMS delay spread" hasn't been a parameter i've been familiar with.
> >is it a measure of overall phase nonlinearity?
>
> Possibly useful:  see US Patent 5375067 for a discussion of Central Time and RMS
> Duration.
>


Greg, i didn't know about this patent of yours. good show!

well, i'm still trying to pin these guys down. if their r.m.s. delay
parameter ("spread" or whatever it's called) is a measure of deviation
from phase linearity, then nothing can beat a phase linear FIR. but
if it's a measure of phase delay or group delay (from zero), then a
minimum-phase filter will beat linear-phase.

that's all i wanted to say about it.

r b-j


From: Steve Pope on
robert bristow-johnson <rbj(a)audioimagination.com> wrote:
>well, i'm still trying to pin these guys down. if their r.m.s. delay
>parameter ("spread" or whatever it's called) is a measure of deviation
>from phase linearity, then nothing can beat a phase linear FIR. but
>if it's a measure of phase delay or group delay (from zero), then a
>minimum-phase filter will beat linear-phase.

It is neither.

Steve
From: Pete Fraser on
"robert bristow-johnson" <rbj(a)audioimagination.com> wrote in message
news:c2f65e9b-74e2-41e3-85f0-61684db85f48(a)k39g2000yqd.googlegroups.com...

> well, i'm still trying to pin these guys down. if their r.m.s. delay
> parameter ("spread" or whatever it's called) is a measure of deviation
> from phase linearity, then nothing can beat a phase linear FIR.

I don't know if there's a formal definition.
I just assumed it was a measure of the dispersiveness
(frequency dependent delay) of the filter.

> but if it's a measure of phase delay or group delay (from zero),
> then minimum-phase filter will beat linear-phase.

True, but I'm not sure why anybody would refer to that
as "spread".

Pete


From: Steve Pope on
Steve Pope <spope33(a)speedymail.org> wrote:

>robert bristow-johnson <rbj(a)audioimagination.com> wrote:

>>well, i'm still trying to pin these guys down. if their r.m.s. delay
>>parameter ("spread" or whatever it's called) is a measure of deviation
>>from phase linearity, then nothing can beat a phase linear FIR. but
>>if it's a measure of phase delay or group delay (from zero), then a
>>minimum-phase filter will beat linear-phase.

>It is neither.

Here's a reference:

Ibnkahla, _Signal Processing for Mobile Communications Handbook_,
section 1.2.2.1.4. It is viewable on Google Books.

He used the same expression for average delay I stated, but
his expression for RMS Delay Spread is a little different,
and I don't like it as much, but I think his expression is
as close to a standard definition as you will get.

RMS delay spread must be used carefully; there are responses with
large RMS delay spreads which do not have bad phase qualities for
a most signals, i.e. something like

h(t) = 1*(t) + 100*(t - 20) - 100*(t - 20.0001)



S.