Subject: Re: [linux-audio-dev] stats please.
From: Andre Majorel (amajorel_AT_teaser.fr)
Date: Sat Oct 13 2001 - 18:45:53 EEST
On 2001-10-13 05:41 -0500, dave willis wrote:
> On Fri, 12 Oct 2001, Ivica Bukvic wrote:
>
> > 2) I am interested in what is the current latency achievable not only for
> > DSP stuff, but also for a MIDI aspect as well, since the last up-to-date
> > benchmarking of this sorts I was able to locate on the net is over a year
> > and a half old and not very comprehensive.
>
> using benno's mididelay, i get about 1.12 ms average, max 1.135966 ms on
> my m-audio audiophile using using an at-keyboard cable (and not a quality
> midi cable). i get the same results when using two cables and routing
> through my yamaha sy85 keyboard. sometime soon i'll try it with my
> roommate's high-quality midi cables.
>
> benno says :
>
> Tn theory since the MIDI interface does run at 31kbps we assume that one
> byte takes about 0.3ms to transmit, therefore a full note-on =3 bytes
> should not take more than 1 - 1.5ms
>
> well, i'm at the low end of that range. however, he's done some bad
> rounding in his math. 31kbps = 1 byte per .252 ms, so .756 ms minimum for
> three bytes.
It's actually 31250 b/s, and IIRC the serial protocol uses 1
start bit and 1 stop bit so that would be 10 * 1/31250 = 320 µs
per MIDI byte.
-- André Majorel <amajorel_AT_teaser.fr> http://www.teaser.fr/~amajorel/
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