Duplex: Pitchbend Always At 1% When Automated

Help, Support & Bugs
1

If I automate the pitchbend using Duplex->Keyboard device->Pitchbend remapper->Midi remapper->Midi automation device, the pitchbend has the middle position at 1%, not 0%, so the pitch is detuned a bit, dependent on the range of the pitchbend.

Shouldn’t it be 0%? I checked the pitchbend values with the midi monitor for OSX, the pitchbend send value 0 in deteched position.

Or is this bug related to duplex?

2

It’s most likely Duplex. I’ll investigate.

3

OK, results are in - and this is in fact a bit weird, has nothing to do with Duplex:
My keyboard will output 64 at the middle position, 0 as minimum and 127 as max. Nothing strange in that.
But I noticed that it’s simply not possible to reach 0% with a 7-bit MIDI controller. When you transmit 63, the pitch bend is set to -1%, and at 64 it becomes 1%.

Now, as we are most likely to deal with an integer range of 128 there is no center value, so what Renoise does is - mathematically speaking - correct.
Unfortunately, pitch bend is traditionally based around the center value and the result is a small, but noticeable different in pitch.

I then checked with other DSPs that have such bipolar parameters, and indeed it’s present in a couple of other places as well:

  • DC Offset: 0.787 % and -0.787 %
  • EQ5/10 : 0.157 dB and -0.157 dB
  • Flanger amount + feedback: 0.787 % and -0.787 %
  • Mixer EQ lo/mid/hi gain: 0.142 dB and -0.142 dB
  • mpReverb low gain: 0.142 dB and -0.142 dB

IMHO pitch-bend is the most important parameter, the others hardly have a noticeable effect on the sound.
The solution would be to pick a value which should represent the center, make a bipolar parameter “center-centric”.
But the big question is, if some keyboard would output e.g. 63 as the center value?

4

Hm, strange. But would be nice if this was fixed by the Renoise team to get really exact results. Isn’t there a common convention are practice dealing with this?

Can’t this fixed by using floor() for the rounding when you convert pitchbend to 7 bit? And are you sure that 63 is pitchbend -1? As far as I can hear the 0%/63 have the pitch 0.

Yes, 64 is 0 pitchbend also on korg.

5

Yes, I just checked the MIDI specification and it implies that 0x40 (64 decimal) is in fact the centered position.

Edit:

I guess it’s a question of making a special treatment for 7-bit MIDI messages, while looking at whether the parameter is uni- or bipolar