Add matric_time and duration_metric_time (#166)

* add matric_time and duration_metric_time

* Update src/midifile.jl

Co-authored-by: George Datseris <[email protected]>

* add documentation

---------

Co-authored-by: George Datseris <[email protected]>

CHANGELOG.md

@@ -4,6 +4,9 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
+# v2.6.0
+* New functions `metric_time`.
+* New functions `duration_metric_time`.
 # v2.5.0
 * Implement `Note(pitch_name::String; position = 0, velocity = 100, duration = 960, channel = 0)`
 * Implement `Notes(notes_string::String, tpq::Int = 960)`

Project.toml

@@ -1,13 +1,15 @@
 name = "MIDI"
 uuid = "f57c4921-e30c-5f49-b073-3f2f2ada663e"
 repo = "https://github.com/JuliaMusic/MIDI.jl.git"
-version = "2.5.0"
+version = "2.6.0"
 
 [deps]
 FileIO = "5789e2e9-d7fb-5bc7-8068-2c6fae9b9549"
+IterTools = "c8e1da08-722c-5040-9ed9-7db0dc04731e"
 
 [compat]
 FileIO = "1"
+IterTools = "1.8.0"
 julia = "1"
 
 [extras]

src/MIDI.jl

@@ -4,6 +4,7 @@ A Julia library for reading and writing MIDI files.
 module MIDI
 
 using Base.Unicode
+using IterTools
 
 include("constants.jl")
 include("note.jl")
@@ -34,6 +35,7 @@ export pitch_to_name, name_to_pitch, is_octave
 export pitch_to_hz, hz_to_pitch
 export TrackEvent, MetaEvent, MIDIEvent, SysexEvent
 export readvariablelength, writevariablelength
+export metric_time,duration_metric_time
 
 """
     testmidi()

src/midifile.jl

@@ -167,11 +167,40 @@ end
 """
     ms_per_tick(tpq, qpm)
     ms_per_tick(midi::MIDIFile)
-Return how many miliseconds is one tick, based
+Return how many milliseconds is one tick, based
 on the quarter notes per minute `qpm` and ticks per quarter note `tpq`.
 """
 ms_per_tick(midi::MIDI.MIDIFile, qpm = qpm(midi)) = ms_per_tick(midi.tpq, qpm)
 ms_per_tick(tpq, qpm) = (1000*60)/(qpm*tpq)
 
 getnotes(midi::MIDIFile, trackno = midi.format == 0 ? 1 : 2) =
 getnotes(midi.tracks[trackno], midi.tpq)
+
+"""
+    metric_time(midi::MIDIFile,note::AbstractNote)::Float64
+Return how many milliseconds elapsed at `note` position.
+Matric time calculations need `tpq` field of `MIDIFile`.
+Apparently it only make sense if the `note` coming from `MIDIFile`, otherwise you can't get the correct result. 
+"""
+function metric_time(midi::MIDIFile,note::AbstractNote)::Float64
+    # get all tempo change event before note
+    tc_tuples = filter(x->x[1]<=note.position,tempochanges(midi))
+    # how many ticks between two tempo changes event
+    tempo_ticks = map(x->x[2][1]-x[1][1],partition(tc_tuples,2,1))
+    push!(tempo_ticks,note.position-last(tc_tuples)[1])
+    return mapreduce(x -> ms_per_tick(midi.tpq, x[1][2]) * x[2], +, zip(tc_tuples,tempo_ticks))
+end
+
+"""
+    duration_metric_time(midi::MIDIFile,note::AbstractNote)::Float64
+Return `note` duration time in milliseconds.
+Matric time calculations need `tpq` field of `MIDIFile`.
+Apparently it only make sense if the `note` coming from `MIDIFile`, otherwise you can't get the correct result. 
+"""
+function duration_metric_time(midi::MIDIFile,note::AbstractNote)::Float64
+    tc_tuple = (0,0.0)
+    for tc in tempochanges(midi)
+        tc[1] <= note.position ? tc_tuple = tc : break
+    end
+    return ms_per_tick(midi.tpq,tc_tuple[2])*note.duration
+end

test/miditrack.jl

@@ -200,7 +200,7 @@ invalidtestvalues = [
         onotes = getnotes(original_track)
         tnotes = getnotes(test_track)
         identical = true
-        for i = 1:length(onotes)
+        for i = eachindex(onotes)
             if onotes[i] != tnotes[i]
                 identical = false
             end
@@ -209,4 +209,17 @@ invalidtestvalues = [
         @test identical
 
     end
+
+    @testset "metric_time" begin
+        midifile = load("./tempo_change.mid")
+        notes = getnotes(midifile.tracks[1])
+
+        @test metric_time(midifile,last(notes)) == 8500.0
+        @test metric_time(midifile,first(notes)) == 0.0
+        @test metric_time(midifile,notes[5]) == 2500.0
+
+        @test round(duration_metric_time(midifile,notes[2])) == 474
+        @test round(duration_metric_time(midifile,last(notes))) == 948
+        @test round(duration_metric_time(midifile,first(notes))) == 474
+    end
 end