midi.py

#!/usr/bin/env python

# Based on code from https://github.com/osakared/midifile.py
# which appears to be based on
# https://github.com/gasman/jasmid/blob/master/midifile.js

# Original license:

"""
Copyright (c) 2014, Thomas J. Webb
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""

import pygame, struct, time, statistics, glob

class Note(object):
    "Represents a single MIDI note"
    
    note_names = ['A', 'A#', 'B', 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#']
    
    def __init__(self, channel, pitch, velocity, start, duration = 0):
        self.channel = channel
        self.pitch = pitch
        self.velocity = velocity
        self.start = start
        self.duration = duration
    
    def __str__(self):
        s = Note.note_names[(self.pitch - 9) % 12]
        s += str(self.pitch // 12 - 1)
        s += " " + str(self.velocity)
        s += " " + str(self.start) + " " + str(self.start + self.duration) + " "
        return s
    
    def get_end(self):
        return self.start + self.duration

class MidiFile(object):
    "Represents the notes in a MIDI file"
    
    def read_byte(self, file):
        return struct.unpack('B', file.read(1))[0]
    
    def read_variable_length(self, file, counter):
        counter -= 1
        num = self.read_byte(file)
        
        if num & 0x80:
            num = num & 0x7F
            while True:
                counter -= 1
                c = self.read_byte(file)
                num = (num << 7) + (c & 0x7F)
                if not (c & 0x80):
                    break
        
        return (num, counter)
    
    def __init__(self, file_name):
        self.tempo = 120
        try:
            file = open(file_name, 'rb')
            if file.read(4) != b'MThd': raise Exception('Not a MIDI file')
            self.file_name = file_name
            size = struct.unpack('>i', file.read(4))[0]
            if size != 6: raise Exception('Unusual MIDI file with non-6 sized header')
            self.format = struct.unpack('>h', file.read(2))[0]
            self.track_count = struct.unpack('>h', file.read(2))[0]
            self.time_division = struct.unpack('>h', file.read(2))[0]

            # Now to fill out the arrays with the notes
            self.tracks = []
            for i in range(0, self.track_count):
                self.tracks.append([])

            for nn, track in enumerate(self.tracks):
                abs_time = 0.

                if file.read(4) != b'MTrk': raise Exception('Not a valid track')
                size = struct.unpack('>i', file.read(4))[0]

                # To keep track of running status
                last_flag = None
                while size > 0:
                    delta, size = self.read_variable_length(file, size)
                    delta /= float(self.time_division)
                    abs_time += delta

                    size -= 1
                    flag = self.read_byte(file)
                    # Sysex messages
                    if flag == 0xF0 or flag == 0xF7:
                        # print "Sysex"
                        while True:
                            size -= 1
                            if self.read_byte(file) == 0xF7: break
                    # Meta messages
                    elif flag == 0xFF:
                        size -= 1
                        type = self.read_byte(file)
                        if type == 0x2F:    # end of track event
                            self.read_byte(file)
                            size -= 1
                            break
                        print("Meta: " + str(type))
                        length, size = self.read_variable_length(file, size)
                        message = file.read(length)
                        # if type not in [0x0, 0x7, 0x20, 0x2F, 0x51, 0x54, 0x58, 0x59, 0x7F]:
                        print(length, message)
                        if type == 0x51:    # qpm/bpm
                            # http://www.recordingblogs.com/sa/Wiki?topic=MIDI+Set+Tempo+meta+message
                            self.tempo = 6e7 / struct.unpack('>i', b'\x00' + message)[0]
                            print("tempo =", self.tempo, "bpm")
                    # MIDI messages
                    else:
                        if flag & 0x80:
                            type_and_channel = flag
                            size -= 1
                            param1 = self.read_byte(file)
                            last_flag = flag
                        else:
                            type_and_channel = last_flag
                            param1 = flag
                        type = ((type_and_channel & 0xF0) >> 4)
                        channel = type_and_channel & 0xF
                        if type == 0xC:    # detect MIDI program change
                            print("program change, channel", channel, "=", param1)
                            continue
                        size -= 1
                        param2 = self.read_byte(file)
                        
                        # detect MIDI ons and MIDI offs
                        if type == 0x9:
                            track.append(Note(channel, param1, param2, abs_time))
                        elif type == 0x8:
                            for note in reversed(track):
                                if note.channel == channel and note.pitch == param1:
                                    note.duration = abs_time - note.start
                                    break

        except Exception as e:
            print("Cannot parse MIDI file: " + str(e))
        finally:
            file.close()
    
    def __str__(self):
        s = ""
        for i, track in enumerate(self.tracks):
            s += "Track " + str(i+1) + "\n"
            for note in track:
                s += str(note) + "\n"
        return s


RES = 650, 440
BACKGROUND = 100, 100, 100
TARGET_FPS = 60     # FPS that PyGame is expcted to run at
SONG_DIR = "goldberg"

def ini(s, res):
    "Load samples"
    global audio

    audio = {}
    for n in range(2, 89):
            # samples are numbered with middle C == 39 (i.e. off by one)
            audio[n] = pygame.mixer.Sound("midisnd/midi%02u.wav" % (n - 1))
            audio[n].set_volume(0.2)

def load_song(s, res, fn):
    "Load song data"
    global notes, t, inc, first, last

    notes = []
    first, last = 1e9, -1
    m = MidiFile(fn)
    for tn in range(len(m.tracks)):
        for n in m.tracks[tn]:
            if n.velocity > 0:
                tt = int(1000 * n.start)
                first = min(first, tt)
                last = max(last, tt)
                notes.append([n.pitch - 20, tt])
    inc = 20    # advance by this many MIDI time units during each PyGame frame
    t = 0
    #print(notes)

def play(s, res, fpsfac, tfac):
    "Play all notes that should trigger during this PyGame frame"
    global t
    s.scroll(dx = -2)
    pygame.draw.rect(s, BACKGROUND, [RES[0]-2, 0, 2, RES[1]])
    # apply user tempo selection and FPS adjustment
    rinc = int(inc * fpsfac * tfac)
    for x, y in notes:
        if t <= y-first < t + rinc:
            audio[x].stop()
            audio[x].play()
            pygame.draw.rect(s, (255,255,255), [RES[0]-2, RES[1]-5*x, 2, 2])
            #print(y, x)
    t += rinc
    # end of song?
    if t <= last + RES[0] * rinc:
        return True
    else:
        return False
        
class MIDI:
    def __init__(self):
        pygame.init()
        pygame.mixer.init()
        self.res = RES
        self.screen = pygame.display.set_mode(self.res)
        pygame.display.set_caption('midi')
        self.screen.fill(BACKGROUND)
        self.clock = pygame.time.Clock()
        ini(self.screen, self.res)
        self.calib = 10
        self.samp = []
        self.last = 0
        self.mlist = sorted(glob.glob(SONG_DIR + "/*.mid"))
        self.mselect = 0
        load_song(self.screen, self.res, self.mlist[self.mselect])
        self.tempo = 1
        self.paused = False

    def events(self):
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                self.running = False
            if event.type == pygame.KEYDOWN and event.key == pygame.K_RIGHT:
                self.mselect += 1
                self.mselect = self.mselect % len(self.mlist)
                load_song(self.screen, self.res, self.mlist[self.mselect])
            if event.type == pygame.KEYDOWN and event.key == pygame.K_LEFT:
                self.mselect -= 1
                self.mselect = self.mselect % len(self.mlist)
                load_song(self.screen, self.res, self.mlist[self.mselect])
            if event.type == pygame.KEYDOWN and event.key == pygame.K_UP:
                self.tempo += 0.05
            if event.type == pygame.KEYDOWN and event.key == pygame.K_DOWN:
                self.tempo -= 0.05
            if event.type == pygame.KEYDOWN and event.key == pygame.K_SPACE:
                self.paused = not self.paused

    def run(self):
        self.running = True
        while self.running:
            self.clock.tick(60)
            self.events()
            self.update()
        pygame.quit()

    def update(self):
        # measure FPS for automatic adjustment
        if self.calib > 0:
            f = 1 / (time.time() - self.last)
            self.last = time.time()
            self.calib -= 1
            self.samp.append(f)
            self.fps = statistics.median(self.samp)
            print("FPS", self.fps)
            return
        self.tempo = max(0.1, min(3, self.tempo))
        pygame.display.set_caption('midi (%s , tempo %.2f)' % (self.mlist[self.mselect], self.tempo))
        if self.paused: return
        # play notes
        if not play(self.screen, self.res, TARGET_FPS / self.fps, self.tempo):
            # advance to next song in playlist
            self.mselect += 1
            self.mselect = self.mselect % len(self.mlist)
            load_song(self.screen, self.res, self.mlist[self.mselect])
            
        pygame.display.flip()

c = MIDI()
c.run()