From rafael2pop@yahoo.com.ar Fri Jun 03 05:34:23 2011
Subject:Re: USB-MIDI (Was: Nord C2 as a Controller) [OT]

Hi All,

Hope each time having here a controversial MIDI topic, Bruce Wahler be sharing again . their knowledge and tips.

Actually it's appreciated !

Best,

Rafael

Re: USB-MIDI (Was: Nord C2 as a Controller) [OT]
Posted by: "Bruce Wahler" bruce@ashbysolutions.com drawbars
Thu Jun 2, 2011 4:00 pm (PDT)

Hi Simon,

Apples and Oranges, I'm afraid.

'Vintage' MIDI is limited to 31.25Kbit/sec, or 3,125 bytes/sec --
roughly, 1K messages per second. That sounds like a lot, but for
complex MIDI setups and data/audio transfer, it's sorely lacking.
Transmitting a 50MB piano sample will take almost 4.5 hours. What makes
it even worse is that MIDI uses 7-bit data, so even sending 100 bytes of
data takes more than 100 bytes! Even real-time use has limits: If a
computer-driven performance needs to send a downbeat on all 16 channels
at once, the attacks will be spread over a 16mS window.

There were a couple of attempts to float a 'MIDI v2' standard, but it
never gained steam, partly because it would obsolete certain older devices.

USB-MIDI runs at much higher speeds, and so it's better for things like
downloading piano samples to an Electro 3. As you noted, though,
USB-MIDI doesn't allow for peer-to-peer connections. This isn't
actually a limitation of MIDI; it's a limitation of USB. USB has
'peripherals' and 'hosts.' It doesn't take much to be a MIDI peripheral:

* The device must support basic USB communications.
* If asked, it must tell the host what kind of device it is, and how
much power it needs.
* If asked for a driver, and it doesn't have one, it must say so.
* If told to shut down, it must obey the command.

That's it. A USB host, however, has to 'chair the meeting,' so to
speak. It has to find out what devices are on the line, calculate if it
can provide enough power, accept/deny new devices, and provide a
mechanism to import new drivers for devices without built-in support.
It also has to support hubs and downstream devices. If things go awry,
it has to shut down the link. It also has to have fail-safe mechanisms
to prevent bad USB devices from crashing the host. Essentially, a USB
host is a small computer. The average smart phone has enough horsepower
to be a USB host, but the average keyboard is using that power for other
purposes.

Also, it costs about $0.50-1.00USD to add MIDI peripheral support to a
production product. It costs 5-10x that much to provide the support for
being a host, plus the CPU cycles.

There is a USB version called OnTheGo (USB-OTG) that allows for a
simpler mechanism, but it has never caught on in the music world. Even
this reduced standard requires a bit of CPU 'quality time.'

By comparison, vintage MIDI is kind of brain-dead. The Out port sends
data at 3K/sec; it doesn't know or care if anyone receives it.

Regards,

-BW

Bruce Wahler
Ashby Solutions.com^ (TM)
bruce@ashbysolution s.com
http://music. ashbysolutions. com
877.55.ASHBY (877.552.7429)

On 6/2/2011 5:06 PM, Simon Beck wrote:
> But why are CERTAIN keyboard manufacturers insisting on trying to kill the MIDI standard by refusing to fit DIN sockets and instead using so-called USB-MIDI, which doesn't allow direct connections between MIDI-compatible instruments?
>