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

[Justin Smith]

On Wed, Apr 1, 2009 at 3:32 AM, Clemens Ladisch <cladisch at fastmail.net> wrote:
> Crypto wrote:
>> I am currently using two external MIDI devices that connect to my notebook via
>> an external USB MIDI adaptor (a nice Edirol UM2).
>> [...]
>> And now there is a problem: as I have connected the two devices to the IN port
>> the application (or the driver of the MIDI port) has to do MIDI merging. But
>> something is wrong with the merging, if the running status device's data
>> bytes have to be merged with the second device's data stream.
>
> 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 an alternative way of interpreting the bytes
(comparable to nrpn or such), so there should be no issue of MIDI or
ALSA incompatibility. I think what he is looking for is a program that
will convert from running status to the standard format, and for that,
all you need is a program that can read the raw midi bytes and
interpret them properly. I think this could be fixed in PD with a half
hour or so of patching, perhaps midish could do it as well. Please
correct me if I am wrong about this.

> That IN port is an ALSA sequencer port, isn't it?
>
> Does the data look correct when you view it with aseqdump?
>
>> 1.) Which part is actually responsible for the MIDI merging of two or more
>> output devices into one input device? Is it the driver of the port or is it
>> the application, that is in the end receiving the MIDI data stream?
>
> Each ALSA sequencer input port has a queue of messages; ALSA
> automatically puts messages into this queue in the correct order.
>
>> 2.) Is it illegal to connect two output devices to one input port?
>
> No.
>
>> 3.) If I should need some kind of virtual MIDI multiplexing/demultiplexing
>> driver: which one should I chose?
>
> Connecting one port to several other ports works without a separate
> device.
>
> In certain situations, you might want to use the MIDI Through device.
>
>
> Best regards,
> Clemens
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>

I think when he is talking about multiplexing, he is talking about
being able to mix midi streams that are using running status, so the
PD or midish process would act as the "multiplexer".