Issue on MidiList::insertRepeatedControllerValue(...)

Tracktion Engine
1

Hi,
I was trying the
MidiList::insertRepeatedControllerValue (int type, int startVal, int endVal, juce::Range<double> beats, double intervalBeats, juce::UndoManager* um)
method the insert multiple controller events.

Now focusing on the second and third parameters ( startVal and endVal ) that i have to pass, they are limited between 0 and 127.

In the method’s body there is this line of code :
auto maxNumSteps = std::max(2, type == MidiControllerEvent::pitchWheelType ? std::abs(rangeValues) : std::abs(rangeValues) >> 7);
that takes the rangeValue = endVal - startVal ( rangeVal can at most be 127 ) and right-shift it of 7 bits given always a 0 result… so maxNumSteps is always 2 ( exept in the case of a pitchWheelType controller ).

The method then calculates the numSteps in this way :
auto numSteps = juce::roundToInt (rangeBeats / intervalBeats);
but then it compares numStep with maxNumSteps and performs numStep = maxNumSteps if the are not equals…
So the numStep is always equal to 2 and independently from rangeBeat it will create only 3 controller events!

How to deal with it ?
Thxs.

2

I think startVal and endVal are 14-bit values.
We should really add a type for this as it’s unclear currently when 7-bit and 14-bit values are used.

3

Yes it can be bery usefull.
So i must leftShift startVal and endVal before pass them to the method ?
For example :

  • 127 << 7 = 16.256
  • 30 << 7 = 3.840

rangeValues = 16.256 - 3.840 = 12.416, so in the method we’ll have 12.416 >>7 = 97.
Am i right ?

4

Yes, that’s the original range you started with.

Its done like that because all MIDI values internally are stored at 14-bit numbers as that the resolution of some MIDI numbers (e.g. pitch wheel, aftertouch IIRC). This will hopefully help us when moving to higher resolution MIDI2 values as well.

5

Ok perfect.
One last question : if i pass (startVal<<7) and (endVal<<7) to the method there will be some errors just because the rangeValues is correct but the value used to create the events is wrong…
Mybe i need to modify the method ?

6

I’m not sure I follow what will be wrong?

7

After evaluating the numStep value there is a loop based on it in which a value is calculated (with the interpolate method) and its value is not more included between 0 and 127, but betwenn 0<<7 and 127<<7.

for (int i = 0; i < numSteps; ++i)
    {
        const int value = interpolate (startVal, rangeValues, beats.getStart(), beat, rangeBeats);
        addControllerEvent (beat, type, value, um);
        beat += intervalBeats;
    }

static int interpolate (int startValue, int rangeValues, double startBeat, double beat, double rangeBeats) noexcept
{
    return juce::roundToInt (startValue + (rangeValues * (beat - startBeat) / rangeBeats));
}

So it will add controller events with an over-range values.

8

But addControllerEvent also expect a 14-bit number so it should be fine.

9

Excuse me but when i call the add controllerEvent ( for example by double clicking on the component ) i pass an int value included between 0 and 127…
So you are telling me that i must always pass a value between 0<<7 and 127<<7 ?
I’m a bit confused.

10

Yes. If the source is a 7 bit value (0-127) shift it up before passing it to the MidiList methods.