Re: [RE] Latencies through RE cables (better URL)
I am not a professional musician, but based on my home PC based music
experience, I sympathize with comment 2.
Dirceu Cavendish
NEC Labs America
10080 North Wolfe Road Suite SW3-350
Cupertino, CA 95014
Tel: 408-863-6041 Fax: 408-863-6099
-----Original Message-----
From: owner-stds-802-3-re@IEEE.ORG [mailto:owner-stds-802-3-re@IEEE.ORG]
On Behalf Of Gross, Kevin
Sent: Wednesday, April 27, 2005 9:31 AM
To: STDS-802-3-RE@LISTSERV.IEEE.ORG
Subject: Re: [RE] Latencies through RE cables (better URL)
I've looked at the scenarios in the paper. I have a couple comments.
1/ No headphone scenarios are considered. A DJ or singer wearing
headphones
is the most critical case I'm aware of with respect to latency. Delays
above
0.5ms are audible and, in many cases, objectionable in this scenario.
This
sort of headphone monitoring is routinely used in home studio recording
(section 1.3.2) and even by some geeky garage musicians (section 1.3.3).
2/ I question whether a 5ms processing delay is achievable through a PC
as
shown in figure 1.3. The PC architecture was not designed for real-time
processing. Delay through a PC is certainly greater than 15ms and can
reach
100ms and beyond. As such, some musicians find it unacceptable to run
their
monitors through the PC; they use external gear to bypass the PC during
tracking. Others, baulk at the cost of the external gear, and learn to
perform well despite the latency.
-----Original Message-----
From: owner-stds-802-3-re@IEEE.ORG [mailto:owner-stds-802-3-re@IEEE.ORG]
On
Behalf Of David V James
Sent: Tuesday, April 26, 2005 3:52 PM
To: STDS-802-3-RE@LISTSERV.IEEE.ORG
Subject: [RE] Latencies through RE cables (better URL)
All,
(The URL has been updated, after David Law
provided a more universally accessible web page).
Things seem to have been quiet for the last week.
Perhaps I could stimulate some discussions on
cable latencies?
I believe Alexei's presentations have claimed that
interactive latencies of 15ms are nearly audible.
Since the link delays are only part of the delay
equation, this has led some of us to believe that
(worst case) per-hop latencies should not exceed
0.5ms. (This number is much more than the speed
of light, since it includes buffer and conflict
delays.)
Is there any controversy with using this as a
working per-hop maximum delay number?
For background material on this topic, please
reference pages 15-17 of the following
working paper:
http://www.ieee802.org/3/re_study/material/index.html
(Thanks again to David Law for his quick posting!!)
I have spent the last week accumulating content
of various slide presentations into the above
listed working paper. Hopefully this will be helpful
when considering this and other issues.
DVJ
David V. James