On Saturday 11 November 2006 21:54, jdow wrote:
>From: "Gene Heskett" <gene.heskett@xxxxxxxxxxx>
>
>> On Saturday 11 November 2006 21:00, Tony Nelson wrote:
>>>At 4:21 PM -0500 11/11/06, Gene Heskett wrote:
>>> ...
>>
>> This thread might be of interest to the linux-audio-dev group, so I've
>>
>> added them to the Cc:
>>>>Yup, and its been a constant src of amazement to this old fart that
>>>> when the midi spec was setup, they used a serial port, thats fine,
>>>> but when they set the data rate at only 31,250 baud, ...
>>>>
>>>>Consistently attrocious timeing, with the horns always 1/16 beat late
>>>>unless the actual output order of each instrument is scrambled in the
>>>>order output. That would make it sound a heck of a lot less
>>>> mechanical. And there isn't a heck of a lot that can be done until
>>>> we put midi on an optical circuit running at several megabytes/sec.
>>>> Something like TOS maybe?
>>>
>>>Firewire. Many products already, plenty of speed, almost robust
>>> enough. 1/8 millisecond isoch cycle times; each cycle can contain
>>> packets from many senders; each packet can contain lots of notes.
>>
>> More robust IMO than the din connectors now used for midi
>> interconnects, however the cabling itself can't help but be more
>> fragile when subjected to the rigors of a jam session with bodies
>> walking on them all night. And that has to be a consideration else the
>> first users will get discouraged at the high cable failure rates and
>> revert, particularly if they have a tin ear and can't hear what to
>> many of us would be an extremely obvious improvement.
>>
>> But I like that idea, a lot. Maybe some enterprising LAD people could
>> get together and spec something like a midi interface running over
>> firewire, complete with the repeaters so it can be daisy-chained just
>> like midi can be, and hopefully release it into the PD as a new midi-2
>> interface standard. And design it such that it never, ever gets into
>> the snails trail of the 31,250 baud interface it uses today.
>
>Runs like snails. But I have seen installations with FAR more cable on
>MIDI runs than the specification suggests is the maximum. (It is off
>by orders of magnitude. I suspect a conforming driver and receiver
>coupled with zip cord could go a half mile and still work - with
>normal timing.
That would be a pretty low impedance cable to drive half a mile of. What
would that be, 15 to 30 ohms? Without well matched load terms the driver
can't handle (I think its limited to 20 ma of drive IIRC), I think the
echo's would tend to cause odd things. OTOH Joanne, I've not recently
looked at a midi cable with a scope to check the data quality either, so
I'm just doing the practical broadcast engineers 'eddycated' guess.
>I can't do that with Ethernet. Can't do it with
>1394 or USB, either. MIDI physical transport layer is indeed slow.
That we agree on, allthough we have at least 3 cables in our 100base-t
system at the tv station that rather handily exceed the recommended max
distance of 180 feet, and are apparently just fine. And its slowly being
rebuilt with gigabit cards, all that video serving from a few G5's is
eating our lunch.
>It is staggeringly robust.)
In every regard but that extremely smashable under a foot din connector.
Thats its achilles heel mechanically.
>{^_^}
--
Cheers, Gene
