Re: [LAU] Running Status v.s "Ordinary" Status and MIDI merging

On Wednesday 01 April 2009 at 19:46:30 Clemens Ladisch wrote:
> Justin Smith wrote:
> > On Wed, Apr 1, 2009 at 3:32 AM, Clemens Ladisch <cladisch@email-addr-hidden>
wrote:
> > > Please note that neither the USB MIDI protocol nor ALSA's sequencer
> > > messages can use running status.
> >
> > If I understand correctly, running status is not an alternative to the
> > MIDI protocol,
>
> It is a part of the MIDI protocol.
>
> > it is an alternative way of interpreting the bytes (comparable to
> > nrpn or such), so there should be no issue of MIDI or ALSA
> > incompatibility.
>
> Running status is a feature of the encoding used by MIDI.
>
> USB MIDI and the ALSA sequencer use different encodings.
>
> A USB MIDI adapter converts from MIDI to the USB MIDI protocol, and the
> USB MIDI driver converts that data back to MIDI. It is not possible to
> detect from the result whether the original MIDI data used running
> status.

Sorry, I do not get it.

I have checked the ports using aseqdump connecting to the two UM2 ports of the
external USB MIDI interface.

aseqdump did not report any error message, so I think I can assume that at
this connection there is no problem running status vs. normal status.

I connected the two UM2 ports to the MIDI Thru port and checked to see if
merging works, got no error messages from aseqdump either. I checked this
both UM2 connectors at a time, then both merged into one output.

I am also not sure if I got the USB MIDI part correctly: what I have is an
external USB device that offers two IN/OUT ports having standard 5 pin DIN
connectors each to connect to other standard MIDI devices. So this device is
not transferring USB MIDI data - it is imho simply converting ordinary MIDI
data into USB data without further manipulation, then inside the notebook
ALSA applications see the UM2 connectors as a standard MIDI hardware port
each.

So the hardware ports that I see denoted as UM2 have got to be ALSA sequencer
ports.

I have never had any issues related to running status vs. normal status before
until I wanted to use keykit to work on incoming MIDI data. This is where I
cannot find what causes the error.

I suspect it is keykit that needs more than one IN port and it is keykit which
cannot merge two different MIDI streams that come in at its IN port - but I
am not yet 101% sure about that. So in contrast to what is normally possible
(connect more than one OUT port to one IN port) keykit cannot do this.

Kind regards,
Crypto.
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Received on Thu Apr 2 00:15:02 2009