[alsa-devel] Help requested: new HSS1394 MIDI back-end

Sean M. Pappalardo - D.J. Pegasus spappalardo at mixxx.org
Sat Jun 9 14:41:05 CEST 2012

On 06/09/2012 01:07 PM, Clemens Ladisch wrote:
>> I just modified Mixxx's SCS.1d script to work with your custom sysex
>> messages and tested with your latest patch. The .1d doesn't actually
>> work 100% with this since Mixxx never receives some of the standard
>> MIDI messages amid all of the sysex ones, and it's much worse when the
>> platter is spinning and sending the tons of messages it does. This
>> could be due to PortMIDI's lack of a callback mechanism, forcing Mixxx
>> to poll it every 1ms because it's much more difficult to reproduce the
>> problem using amidi -d.
> That's possible.  However, at 4 KB, ALSA's buffer should be big enough
> for those messages.

Yes, I subsequently found out that it was a bug in Mixxx's PortMIDI 
code. I've corrected that and it works much better now. (Nothing like a 
demanding device to ferret out bugs, eh?)

>> As soon as I start the JACK server to handle the audio interface on
>> the SCS.1m, the ALSA driver stops sending MIDI for that device unless
>> I stop JACK and power-cycle the device. Its last words are:
>> F0 00 01 60 48 53 53 0F 03 00 03 00 00 0B 01 F7
> This is a ping response (tag F3).  Apparently, Jack's FFADO driver
> reinitializes the device and registers its own address for received
> packets.  Since it does _not_ handle MIDI messages, it really should
> not do this.

I think the test-scs program uses JACK-MIDI, so that might be why. But 
test-scs is obsoleted by your driver. I'm CC'ing the FFADO-devel list so 
they can take a look.

Sean M. Pappalardo
"D.J. Pegasus"
Mixxx Developer - Controller Specialist

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