Hi Jan,
On Mon, 2007-12-03 at 17:18 +0100, Jan Jockusch wrote: > Hello Mixxx developers, > > after having contributed a tiny little PowerPC / OGG patch to Mixxx > (worth about 1 bit changed in the executable), I'm now after something > bigger. > > I've just received my Mixman DM2 (a lowcost USB controller which has a > MIDI based driver for Windows and almost nothing for Linux) and am in > the process of writing a Linux kernel driver for it, because there are > several shortcomings in the existing drivers. > > My main criticism is that MIDI based drivers obviously cannot make full > use of the two wheel controls (which are more like mouse axes), for > instance to scroll through the title list, to roll through the songs and > to nudge songs. > > I'd like to change that, but I need some advice on the interfacing layer > with Mixxx. > > The plan is as follows: I write a driver for the DM2 which opens a MIDI > channel (quite the usual method, as I gather). Through this MIDI > channel, I can transmit keypresses and controls like volume, fader, etc. > Up to that point, it's trivial and should work with no problem. > > For the turntables, I will transmit keypresses of varying velocity (the > velocity will encode how much the wheel has moved during that period). > I'll use a different key for clockwise and counter-clockwise motion. > > When the wheel spins very fast, the MIDI channel will see many very > strong keypresses. When it spins slowly, there will still be many > keypresses (to get enough time resolution), but they'll have low > velocity values. When you nudge quickly, then let go of the wheel, > there'll be a couple of keypresses, first with higher, then with lower > velocity. > > This scheme matches up neatly with the way the DM2 transmits its data > (differences in position for the two wheels), and I think the "pulsed > keypress" scheme can work in many situations where you cannot use linear > MIDI controls. > > Now for my catalog of questions: > > - Is this idea any good? (meaning: am I missing a better idea someone > else thought of already?) I'll leave all the MIDI/jog wheel comments up to Ben and others because I'm not familiar with it, but I will say that Andre Roth has already been working on an ALSA MIDI driver for the DM2. The last time we spoke he sent me this link to the latest version of his driver: http://prophet.homelinux.org/~lynx/usbdm2/usbdm2-2007-10-15.tar.gz If you'd like to get in contact with him, email me off-list and I'll send you his email. Alternatively, if Andre's reading the list, maybe he can comment? Albert ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ Mixxx-devel mailing list Mixxx-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mixxx-devel
