Re: [RE] Latencies through RE cables (better URL)
Kevin:
To your item #2, you are probably correct with the PC architecture, but
a lot of these garage musicians buy the MacIntosh just for this reason
as it has a more real time operating system. Apple announced enhanced
sales volumes last quarter of the Mac along with iPod.
Michael, do you have any insight into the processing delay numbers for
the Mac?
Cheers,
Richard
Gross, Kevin wrote:
>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
>
>
>
>
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fn:Richard Brand
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