Biofeedback System

Fire_Dragon4u

I am designing a biofeedback system and before I spend a lot of time going forward I would like to know if others here think what I am planning to do is feasible or have better ideas.

I want to have four different stereo musical tones (8 channels of audio) playing at the same time. Each stereo tone is related to a pair of EEG signal, one on each side. I want to update the volume levels on all eight channels 3 times a second based on the physiological data. So the person will hear the tones louder as they move toward the more desirable states.

My idea is to have two SB live cards so I have the four stereo channels. Using the KX WDM Audio Drivers, I route one midi channel to each stereo output. Then I will have left and right volume control on each midi channel. I play a constant note on each midi channel then programmically update the volume 3 times a second.

I set this up just using the control applets and it works just changing the volumes with a mouse but I am not sure if I can do all this at the rate I want within a program. I am doing all the data acquisition and signal processing using Labview and I would like to integrate the KX mixer into the Labview code. I have never done anything like this before but I feel that it can be done. If anyone sees a problem with this I would really appreciate your comments.

Thanks

Doug W

Personally, I haven't done anything before with kX automation, but I would guess you need to somehow interface Labview with that applet. There are others here who know a lot more about that stuff and will maybe join the discussion.

Maddogg6

if you can use WinAPI from Labview - you can use (MIDIOUTSHORT()) and send MIDI volume (CC#7) to the different MIDI channels. No need for kX automation.
Just...
Open what ever midi OUT ports (KX Synth 1 Card 1 & kX Synth 1 Card 2)
send MIDI notes and CC#7 ($B0) to opened midi OUT ports.
edit / Send these notes and CC #7's to 8 different Midi Channels - and set kXRouter to use seperate FXBuss lines so you can rout them to seperate physical outputs. - so yes you need to adjust the kX DSP - just ask and Ill post an example you could load. / edit.

Pretty simple really. just make sure you load in some Sound Fonts so the midi notes sent will make sounds.

Fire_Dragon4u

Thanks Maddogg. The midi control change 7 changes both the left and right equally and what I need is independent control. The pan CC #10 lowers the right and raises the left or visa-versa so that will not work for me either.

I came up with an easy solution and it sees to work with only one small problem that I can live with. I eliminated the left speaker from both outputs. I created duplicate notes on two midi channels - same note, same velocity, same patch. Then I used the CC 7 to change the volume. I routed the midi channels so that the second right output became effectively the left output. I scaled it up to 8 channels and it worked fine. Although klugey, It saved me from using a second sound card and a lot of programming that is out of my skill set.

The only problem is that if I pick the wrong patch I hear a beat frequency. Since the left and right notes, although duplicates, are being synthesized independently the vibrato or something is out of phase. It only happens on certain patches so I just avoided used them.

Maddogg6

Hmm - you should have been able still using more MIDI channels...

Note PAN CC #10 OR use MIDI 'Balance' - but Im not sure that works in kX ?? its in the MIDI implementation chart if Im not mistaken.. *looking* yup CC#8

Channel 1 Panned left - adjust w/ CC#7
Cahnnel 2 Panned Right - adjust w/ CC#7
.....
Channel 8 Panned right - adjust w/ CC#7

All 8 are independently controlled and no interaction from pan or balance..

But it seems you have it figured out anyway...