midi-file | Parse and write MIDI files | Audio Utils library

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:

Using this thread I have figured out how to use getData(), but instead of getting anything with 0x51, I am getting random values such as [B@37d78d93, [B@29d74462 and [B@1c5ca652

Outputting the meta message itself also results in similar values such as javax.sound.midi.MetaMessage@364d4fca, javax.sound.midi.MetaMessage@5581f86d and javax.sound.midi.MetaMessage@3f011b2b

For example, using

System.out.print ("the meta message is " + mm + ", ");

System.out.print ("the type of meta message is " + mm.getType());

System.out.println(" and the data is " + mm.getData());

outputs

the meta message is javax.sound.midi.MetaMessage@3f011b2b, the type of meta message is 81 and the data is [B@1c5ca652

How can I use the value at the end of the outputted mm value or the values taken from mm.getData() to get the tempo of a MIDI file?

I want to convert a sequence of notes (defined by time, duration, pitch) to a audio-file. For doing so, I thought creating a midi first and then compile it to wav is the way to go.

I'm quite new to audio processing and MIDI-Files, so even though I read several tutorials, it can be, that I didn't get the point.

Edit: I found the problem, see solution below.

What's the problem

Writing notes at a specific time with a specific duration via python's MIDIUtil doesn't work as expected. In fact, the time in seconds, where a note is placed heavily depends on the track's bpm, even though I think I took the bpm into account, when converting the note time to MIDI's time measure in quarter notes.

What I've tried

I'm creating a MIDI track with a given bpm. Then I'm converting a note's event time via t_{quarter} = t_{seconds} * bpm/60

Example

I'm writing with the following code two notes, the last at t=5 seconds with a duration of 1s; i.e. I'm expecting a midi-file with lasts 6seconds. But at a bpm=600, the file is 14s long. At a bpm=100 it's almost the expected 6s.

Here's my code

I want to play an Audio file (A wav file for example) and at specific locations of the track I want to fire events or triggers that will control an external device.

My idea for now is to generate a MIDI track that plays in sync with the Audio Track and when the MIDI track notes are played, some trigger events are generated that we can handle to do whatever we want.

The thing where I am stuck right now is how to play the .mid file and generate events when midi notes are played. I also want to play the wav and the mid file in sync, but that is not what I am solving at this point.

I looked into AudioKit, but the examples seem out of date and the documentation isn't helping a lot.

Is MIDI a right approach to do this? is there an easier way in iOS where I don't have to use AudioKit and just use something from AVFoundation.

I want to understand what tool is best to detect when a midi note from the .mid file is played and handle the event.

My research has pointed me to use AKAppleSequencer. What could help is a simple example that loads a midi file and then basically prints something when a note is played.

I came across these posts,

How to connect AKSequencer to a AKCallbackInstrument?

Play MIDI file together with wav AudioKit

but the AKSequencer is now replaced by AKAppleSequencer.