[alsa-devel] How to add a new MIDI device to the usbaudio driver

[Daniel Mack]

On Thu, Aug 25, 2011 at 1:28 PM, Kristian Amlie <kristian at amlie.name> wrote:
> One caveat I have discovered with the patch: If you keep the instrument
> plugged in, but reload the driver, then the driver gets out of sync with
> the MIDI messages and won't report any. This seems to be because, in the
> stream, the message type is cached and subsequent messages do not report
> what type of message they are unless they are switching to a new type
> (going from control message to note message, for example). You can reset
> the stream by manually generating MIDI messages of different types (turn
> the volume knob while pressing a few notes), or eventually the
> instrument will reset itself and send the type anyway. So it's not
> critical, but would be nice to fix. I'm not sure how to solve it though...

What you're seeing here is a general problem of the MIDI protocol that
cannot be fixed. If a receiver misses the running state update, it
can't do anything but wait for the next one.


Daniel