Re: MIDI

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At 8:28 PM -0800 11/11/06, jdow wrote:
>From: "Tony Nelson" <[email protected]>
>> At 9:41 PM -0500 11/11/06, Gene Heskett wrote:
>>>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.
>>
>> It's already done.  MIDI runs over Firewire, along with audio.  Google for
>> "midi firewire".  Buy it now.
>
>Look at its specs. It is designed to closely mimic wire transport. So
>any given chunk of virtual wire is going to be as slow as MIDI wires.
>...

How can that be?  MIDI latency is determined by the bit rate of serial
transport.  Firewire MIDI latency is improved by the high bit rate, delayed
only by the 8 per ms Isoch frame rate.  There's no need for greater than
1/4 ms latency on Firewire MIDI for even a large number of MIDI events
(notes, aftertouch, what have you).
-- 
____________________________________________________________________
TonyN.:'    The Great Writ     <mailto:[email protected]>
      '      is no more.             <http://www.georgeanelson.com/>


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