Merge pull request #82 from JoelHobson/Notes

Notes, BPM, ms_per_tick

Author: JoelHobson

README.md

@@ -56,19 +56,22 @@ MIDIfile = readMIDIfile("test.mid")
 writeMIDIfile("filename.mid", MIDIfile)
 ```
 
+Two functions that may also be of use are: `BPM(midi)` and `ms_per_tick(midi)`.
+
 Creating a new file with arbitrary notes
 ----------------------------------------
 
 ```
 # Arguments are pitch (MIDI note number), duration (in ticks), position in track (in ticks), channel (0-15) and velocity (0-127)
-C = MIDI.Note(60, 96, 0, 0)
-E = MIDI.Note(64, 96, 48, 0)
-G = MIDI.Note(67, 96, 96, 0)
+using MIDI
+C = Note(60, 96, 0, 0)
+E = Note(64, 96, 48, 0)
+G = Note(67, 96, 96, 0)
 
 inc = 96
-file = MIDI.MIDIFile()
-track = MIDI.MIDITrack()
-notes = MIDI.Note[]
+file = MIDIFile()
+track = MIDITrack()
+notes = Notes()
 i = 0
 for v in values(MIDI.GM) # GM is a map of all the general MIDI instrument names and their codes
     push!(notes, C)
@@ -79,15 +82,15 @@ for v in values(MIDI.GM) # GM is a map of all the general MIDI instrument names
     C.position += inc
     E.position += inc
     G.position += inc
-    C = MIDI.Note(60, 96, C.position+inc, 0)
-    E = MIDI.Note(64, 96, E.position+inc, 0)
-    G = MIDI.Note(67, 96, G.position+inc, 0)
+    C = Note(60, 96, C.position+inc, 0)
+    E = Note(64, 96, E.position+inc, 0)
+    G = Note(67, 96, G.position+inc, 0)
     i += 1
 end
 
-MIDI.addnotes(track, notes)
+addnotes(track, notes)
 push!(file.tracks, track)
-MIDI.writeMIDIfile("test_out.mid", file)
+writeMIDIfile("test_out.mid", file)
 ```
 
 Data structures and functions you should know
@@ -138,6 +141,8 @@ end
 
 Value is a number indicating pitch class & octave (middle-C is 60). Position is an absolute time (in ticks) within the track. Please note that velocity cannot be higher than 127 (0x7F). Integers can be added to, or subtracted from notes to change the pitch, and notes can be directly compared with ==. Constants exist for the different pitch values at octave 0. MIDI.C, MIDI.Cs, MIDI.Db, etc. Enharmonic note constants exist as well (MIDI.Fb). Just add 12*n to the note to transpose to octave n.
 
+In addition, the alias `Notes = Vector{Note}` is also exported for ease-of-use.
+
 ```
 type MIDIEvent <: TrackEvent
     dT::Int

src/MIDI.jl

@@ -3,11 +3,11 @@ A Julia library for reading and writing MIDI files.
 """
 module MIDI
 
+include("note.jl")
 include("trackevent.jl")
 include("midievent.jl")
 include("metaevent.jl")
 include("sysexevent.jl")
-include("note.jl")
 include("miditrack.jl")
 include("midifile.jl")
 include("constants.jl")

src/midifile.jl

@@ -1,4 +1,5 @@
 export MIDIFile, readMIDIfile, writeMIDIfile
+export BPM, ms_per_tick
 
 """
     MIDIFile <: Any
@@ -27,7 +28,7 @@ end
 
 """
     readMIDIfile(filename::AbstractString)
-Read a file into a MIDIFile data type.
+Read a file into a `MIDIFile` data type.
 """
 function readMIDIfile(filename::AbstractString)
     if length(filename) < 4 || filename[end-3:end] != ".mid"
@@ -79,3 +80,43 @@ function writeMIDIfile(filename::AbstractString, data::MIDIFile)
 
     close(f)
 end
+
+
+"""
+    BPM(midi)
+Return the BPM where the given `MIDIFile` was exported at.
+"""
+function BPM(t::MIDI.MIDIFile)
+  # META-event list:
+  tlist = [x for x in t.tracks[1].events]
+  tttttt = Vector{UInt32}
+  # Find the one that corresponds to Set-Time:
+  # The event tttttt corresponds to the command
+  # FF 51 03 tttttt Set Tempo (in microseconds per MIDI quarter-note)
+  # See here (page 8):
+  # http://www.cs.cmu.edu/~music/cmsip/readings/Standard-MIDI-file-format-updated.pdf
+  for i in 1:length(tlist)
+    if typeof(tlist[i]) == MIDI.MetaEvent
+      y = tlist[i]
+      if y.metatype == 0x51
+        tttttt = y.data
+      end
+    end
+  end
+  # Get the microsecond number from tttttt
+  unshift!(tttttt , 0x00)
+  u = ntoh(reinterpret(UInt32, tttttt)[1])
+  μs = Int64(u)
+  # BPM:
+  BPM = round(Int, 60000000/μs)
+end
+
+"""
+    ms_per_tick(midi, bpm::Integer = BPM(midi)) -> ms::Float64
+Given a `MIDIFile`, return how many miliseconds is one tick, based
+on the `bpm`. By default the `bpm` is the BPM the midi file was exported at.
+"""
+function ms_per_tick(midi::MIDI.MIDIFile, bpm::Int = BPM(MIDI))
+  tpq = midi.timedivision
+  tick_ms = (1000*60)/(bpm*tpq)
+end

src/miditrack.jl

@@ -142,11 +142,11 @@ function addnote(track::MIDITrack, note::Note)
 end
 
 """
-    addnotes(track::MIDITrack, notes::Vector{Note})
+    addnotes(track::MIDITrack, notes::Notes)
 Add given `notes` to given `track`, internally doing all translations from
 absolute time to relative time.
 """
-function addnotes(track::MIDITrack, notes::Array{Note, 1})
+function addnotes(track::MIDITrack, notes::Notes)
     for note in notes
         addnote(track, note)
     end
@@ -161,7 +161,7 @@ the `Note` datatype provided by this Package. Ordering is done based on position
 There are special cases where NOTEOFF is actually encoded as NOTEON with 0 velocity.
 `getnotes` takes care of this.
 
-Returns: `Vector{Note}`.
+Returns: `Notes` (which is `Vector{Note}`).
 """
 function getnotes(track::MIDITrack)
     notes = Note[]

src/note.jl

@@ -1,8 +1,9 @@
-export Note
+export Note, Notes
 
 """
     Note <: Any
-Data structure describing a "music note".
+Data structure describing a "music note". The alias `Notes = Vector{Note}` is also
+provided.
 ## Fields:
 * `value::UInt8` : Pitch, starting from C0 = 0, adding one per semitone (middle-C is 60).
 * `duration::UInt` : Duration in ticks.
@@ -27,6 +28,8 @@ type Note
         end
 end
 
+Notes = Vector{Note}
+
 import Base.+, Base.-, Base.==
 
 +(n::Note, i::Integer) = Note(n.value + i, n.duration, n.position, n.channel, n.velocity)