Is there a way to simply tell which channels are in use in a midi file?

[Jenix-Park]

Is there a way to simply tell which channels are in use in a midi file for both the SingleTrack and MultiTrack types?
If I'm not wrong, a MIDI file contains only track-related metadata, but not channel.
So I think I need to iterate over all the timed events and see all the channel numbers used.
But also I think there should be a better way, so I'm asking.

Another question is to make sure that what I understood is correct.
Modifying objects returned by the getters such as GetTrackChunks(), GetChannels(), GetNotes() won't be saved when I call MidiFile.Write() because it's only possible via managers, or the special methods like RemoveNotes() and ProcessNotes(), right?

[melanchall]

1. You can use GetChannels method. But you're right, you need to iterate over all MIDI events in a file. Saving kind of metadata creates more troubles than profit. Because every file modification requires to update that metadata, and there are a lot of ways to change MIDI file and all those ways need to properly update cached metadata.
2. Absolutely correct. Except GetTrackChunks. This method returns the same chunks a MIDI file contains. So direct operations on these chunks (for example, GetTrackChunks().First().Events.First().DeltaTime = 20;) will go to result file.

[Jenix-Park]

Thank you very much!
I love this library so much.
The only downside is this supports C# only.
I wish other MIDI libs for other languages were like this good.

[Jenix-Park]

Does the same apply to the tempo map?
I mean, do I need to call MidiFile.ManageTempoMap() and then TempoMap property instead of directly accessing MidiFile.GetTempoMap()?

[melanchall]

Yes, you need to use manager class to change a tempo map. GetTempoMap just returns current tempo map as immutable object.