Is MIDI tick a fixed value or depends on the BPM of the file?

Question

I'm writing a deep learning automatic composer using RNN. Obviously i need to train it and I decided to use MIDI file format as input.

So far i wrote my input code and my model, but i had some problems reading the input MIDI.

This is my "reading" part of code:

from mydy import Events, FileIO, Containers
test=FileIO.read_midifile('file2.mid') #returns a Pattern with the MIDI file information (resolution ecc...), based on documentation https://github.com/jameswenzel/mydy/blob/master/src/FileIO.py
print(test) #I have to figure out how time is managed

Where i'm using this library which is the Python3 compatible version of this other one (which is only Python2 compatible)

The result i get is the following one:

 mydy.Pattern(format=0, resolution=96, tracks=\
[mydy.Track(relative: True\
  [mydy.TrackNameEvent(tick=0, text='', data=[]),
   mydy.TimeSignatureEvent(tick=0, data=[4, 2, 36, 8]),
   mydy.TimeSignatureEvent(tick=0, data=[4, 2, 36, 8]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[60, 100]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[64, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[60, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[62, 100]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[67, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[62, 64]),
   mydy.NoteOffEvent(tick=0, channel=0, data=[64, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[64, 100]),
   mydy.NoteOffEvent(tick=0, channel=0, data=[67, 64]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[64, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[67, 100]),
   mydy.NoteOnEvent(tick=384, channel=0, data=[66, 100]),
   mydy.NoteOffEvent(tick=0, channel=0, data=[67, 64]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[66, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[67, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[67, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[69, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[69, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[71, 100]),
   mydy.NoteOnEvent(tick=384, channel=0, data=[60, 100]),
   mydy.NoteOffEvent(tick=0, channel=0, data=[71, 64]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[60, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[62, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[62, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[64, 100]),
   mydy.NoteOffEvent(tick=375, channel=0, data=[64, 64]),
   mydy.NoteOnEvent(tick=9, channel=0, data=[67, 100]),
   mydy.NoteOnEvent(tick=384, channel=0, data=[66, 100]),
   mydy.NoteOffEvent(tick=0, channel=0, data=[67, 64]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[66, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[67, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[67, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[69, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[69, 64]),
   mydy.NoteOnEvent(tick=0, channel=0, data=[71, 100]),
   mydy.NoteOffEvent(tick=384, channel=0, data=[71, 64]),
   mydy.EndOfTrackEvent(tick=0, data=[])])])

Which is fine to me.

The problem is: how is MIDI tick managed? Is it a fixed value for each "type" of note?

For example, if i have a quarter note, i will always have (for example) 100 tick, indipendetly on the BPM of the original MIDI file?

For example, if i open a MIDI file written at 100 BPM in a DAW, and then i open a file written at 150 BPM, a quarter note will always correspond to 100 tick? (in both cases)

Since i have many midi files at different BPM, i obviously need a uniform representation of my input for my deep network.

I read the documentation but i'm a bit confused. Especially here when it says:

This message is important if the MIDI time division is specified in "pulses per quarter note", as such MIDI time division defines the number of ticks per quarter note, but does not itself define the length of the quarter note. The length of the quarter note is then defined with the set tempo meta message described here.

Answer 1

The ticks per quarter note or "resolution" is a variable per file in MIDI, and given in the header of the file. Looks like the library you use is making it available to you as resolution=96.

The tempo (BPM) itself is embedded in the MIDI stream (along with the notes) as it can change at any point through the track. By default it is assumed to be 120 BPM.

You can find this information and lot more in the MIDI file spec, e.g. here: http://www.music.mcgill.ca/~ich/classes/mumt306/StandardMIDIfileformat.html