Help with multiple tracks

[grantbrown]

I think I must be missing something obvious, but I can't get multiple tracks to work. Based on the example here, I put together the following minimal example:

using MIDI
C = Note(60, 96, 0, 192)
E = Note(64, 96, 48, 144)
G = Note(67, 96, 96, 96)

inc = 192
file = MIDIFile()
track1 = MIDITrack()
track2 = MIDITrack()
notes1 = Notes() # tpq automatically = 960
notes2 = Notes() # tpq automatically = 960

push!(notes1, C)
push!(notes1, E)
push!(notes1, G)

push!(notes2, C)
push!(notes2, E)
push!(notes2, G)

addnotes!(track1, notes1)
addnotes!(track2, notes2)
addtrackname!(track1, "simple track")
addtrackname!(track2, "simple track2")
push!(file.tracks, track1)
push!(file.tracks, track2)
writeMIDIFile("test.mid", file)

This results in a file that won't play (Internal data stream error), but no errors are raised in Julia. Thoughts?

[Datseris]

https://github.com/JuliaMusic/MIDI.jl/blob/master/src/midifile.jl#L31 the default MIDIFile has type 0. Can you try with file = MIDIFile(1,960,MIDITrack[]) instead, which is the type for multitrack???

[Datseris]

I think that's the problem. From wikipedia:

[grantbrown]

That did the trick, thanks! Would it be worth adding something like the following to the fileio_save methods, or do you want to leave it up to the users? I'm happy to test and put together a pull request if that would be useful.

if (data.format == 0 && length(tracks.tracks) > 1)
    @warn("MIDI file-type 0 only supports a single track")
end

Alternatively, is there more work to do merging the tracks into a single track?

[Datseris]

The warning code you posted seems like a really good idea, yes please do a PR that adds this to the save function. I would not add more info to the documentation string though.

[Datseris]

In the same PR I think it is worth to make the default MIDIFile() make a type 1 format instead of 0. This is not a breaking change because the default type is not documented to begin with.