[cp-patches] Re: Patch: start of ALSA MIDI provider code

[Anthony Green]

On Sun, 2005-10-02 at 01:01 -0700, Anthony Green wrote:
> Here's the start of ALSA MIDI provider code.  MIDI IN ports basically
> work.  You can read and print events from a MIDI keyboard using the
> standard interfaces.  It's not perfect, but it's a start.
> 

I you don't have any MIDI gear and still want to try this, you can use a
virtual MIDI keyboard from here:

http://mitglied.lycos.de/iwai/alsa.html

It's a tcl/tk app that implements a GUI software keyboard that hooks
into the ALSA MIDI system.  If you're using an RPM based distro, you can
try rebuilding the SRPM here. 

http://ccrma.stanford.edu/planetccrma/software/soundapps.html#SECTION000427900000000000000

Be sure to %define your distro at the top of the spec file.  For
instance, I added "%define fc4 1"

Fire up vkeybd, and you should see it when you run aconnect like so:

$ aconnect -i -l
client 0: 'System' [type=kernel]
    0 'Timer           '
    1 'Announce        '
        Connecting To: 63:0
client 62: 'Midi Through' [type=kernel]
    0 'Midi Through Port-0'
client 72: 'USB O2' [type=kernel]
    0 'USB O2 MIDI 1   '
client 128: 'Virtual Keyboard' [type=user]
    0 'Virtual Keyboard'


Now the following program will hook a MIDI receiver up to the Virtual
Keyboard and print something whenever you press a key on the vkeybd GUI.
Note that the code I submitted last night doesn't understand the NOTEOFF
messages from this keyboard.  That's a quick fix.  The hardware keyboard
I tested with send NOTEON with velocity of 0 instead of NOTEOFF.

import javax.sound.midi.*;

public class mtest implements Receiver
{
  public static void main(String args[]) throws Exception
  {
    MidiDevice.Info[] aInfos = MidiSystem.getMidiDeviceInfo();
    MidiDevice inport = null;
    for (int i = 0; i < aInfos.length && inport == null; i++)
      {
        if (aInfos[i].getName().equals ("Virtual Keyboard"))
          inport = MidiSystem.getMidiDevice(aInfos[i]);
      }
    if (inport != null)
      {
        // Hook the keyboard up to our receiver (this class).
        Transmitter t = inport.getTransmitter();
        t.setReceiver (new mtest ());
        // Just sit and wait until a key is pressed.
        System.in.read();
      }
    else
      System.err.println ("Couldn't find Virtual Keyboard");
  }

  public void close()
  {
  }

  public void send(MidiMessage message, long timeStamp)
        throws IllegalStateException
  {
    // This gets called when we receive a MIDI message.
    System.out.println (message);
  }
}