[alsa-devel] Help requested: new HSS1394 MIDI back-end
Sean M. Pappalardo - D.J. Pegasus
spappalardo at mixxx.org
Fri May 25 21:43:17 CEST 2012
I am a developer for Mixxx, GPL cross-platform digital DJ software:
http://www.mixxx.org. My focus is the controller subsystem. I am ready
to finally add Linux support for HSS1394 DJ controllers such as
Stanton's SCS.1m and SCS.1d.
HSS1394 is just MIDI over IEEE1394 (Firewire) at wire speed. The Windows
and OSX library source code is LGPL and available on LaunchPad here:
The Stanton SCS.1m is a sound interface integrated with a two-way
control surface that speaks HSS1394. (The sound card uses an Oxford chip
set and works fine with FFADO 2.0.1 today up to 96kHz. I use it with
Mixxx via JACK.)
The Stanton SCS.1d is a two-way control surface (no sound card) that
speaks HSS1394 and is capable of sending ALOT of latency-sensitive data:
about 4000 messages per platter rotation. (Now imagine if you had four
or even two of them on the same network running at +50% speed. This
would quickly overwhelm USB, at least at the time these devices were
Read about them here:
After a lengthy discussion on the FFADO mailing list, we determined that
the best (cleanest and most flexible) way to get Linux support for these
devices is to write an ALSA kernel driver that speaks HSS1394 with the
devices and presents an ALSA MIDI device (with no data rate limits) for
each to Linux applications.
The advantage of doing this is that the devices will appear to all MIDI
applications without them having to have specific support for HSS1394.
This means they could be used in DAW applications as well.
(FWIW, FFADO trunk has a program called test-scs that does exactly this,
but using that is impractical because it depends on various internal
parts of the FFADO source so would require bundling all of FFADO with
the application, and it's unable to see non-audio devices due to FFADO's
intended use (so it sees the SCS.1m but not the .1d.))
So my questions are: where can I find documentation on writing a new
MIDI driver for ALSA? And is anyone else interested in helping me do this?
Thank you very much for your time and work. Help me take the last step
to my dream DJ setup! (Linux, FLAC and SCS.1 controllers.)
Sean M. Pappalardo
Mixxx Developer - Controller Specialist
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