Calculating timestamps

[sandrojologua]

Hello there, what is the best way to calculate timestamps of notes/beats using alphatab library? I see that alphatab uses midi to retrieve timestamps, but I find it little bit hard to understand. Is there any fast and efficient way to do this calculation only? with or without midi?
Thanks.

[Danielku15]

Yes, alphaTab is handling internally things in Midi ticks and translating it to real timestamps requires some calculations which depend on the current tempo (BPMs).

If you explain a bit more what you want to build, then I can provide you already some snippet/example how to achieve your goal.

The topic can be tricky because of following reasons:

• Songs can have repeats and repeat endings having a big influence when a beat might be played the first time.
• You can change the playback speed (e.g. speed trainer) which change the millisecond position.
• Midi ticks are a tempo (BPM) independent time axis. To translate ticks to milliseconds involves looking at the tempo changes happening during the song.

#1580

Some hints:

• During playback you get the information in ticks and milliseconds at any time:
  https://www.alphatab.net/docs/reference/api/playerpositionchanged/
• The MidiTickLookup (low level apis) is a component filled when we translate the song into midi and it holds more accurate midi tick information with repeats and tempo changes respected.https://www.alphatab.net/docs/reference/api/tickcache#miditicklookupfindbeat-signatures
• Internally in alphaTab there are functions to translate this info.

  alphaTab/src/synth/MidiFileSequencer.ts

  Line 292 in d28966d

  private tickPositionToTimePositionWithSpeed(state: MidiSequencerState, tickPosition: number, playbackSpeed: number): number {

In Guitar Pro there is a feature to show timestamps above bars. But we don't have this on the feature roadmap yet.