# Copyright 2016 Google Inc. All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. """MIDI ops. Input and output wrappers for converting between MIDI and other formats. """ from collections import defaultdict import sys # pylint: disable=g-import-not-at-top if sys.version_info.major <= 2: from cStringIO import StringIO else: from io import StringIO # internal imports import pretty_midi import tensorflow as tf from magenta.protobuf import music_pb2 # pylint: enable=g-import-not-at-top # The offset used to change the mode of a key from major to minor when # generating a PrettyMIDI KeySignature. _PRETTY_MIDI_MAJOR_TO_MINOR_OFFSET = 12 class MIDIConversionError(Exception): pass def midi_to_sequence_proto(midi_data): """Convert MIDI file contents to a tensorflow.magenta.NoteSequence proto. Converts a MIDI file encoded as a string into a tensorflow.magenta.NoteSequence proto. Decoding errors are very common when working with large sets of MIDI files, so be sure to handle MIDIConversionError exceptions. Args: midi_data: A string containing the contents of a MIDI file or populated pretty_midi.PrettyMIDI object. Returns: A tensorflow.magenta.NoteSequence proto. Raises: MIDIConversionError: An improper MIDI mode was supplied. """ # In practice many MIDI files cannot be decoded with pretty_midi. Catch all # errors here and try to log a meaningful message. So many different # exceptions are raised in pretty_midi.PrettyMidi that it is cumbersome to # catch them all only for the purpose of error logging. # pylint: disable=bare-except if isinstance(midi_data, pretty_midi.PrettyMIDI): midi = midi_data else: try: midi = pretty_midi.PrettyMIDI(StringIO(midi_data)) except: raise MIDIConversionError('Midi decoding error %s: %s' % (sys.exc_info()[0], sys.exc_info()[1])) # pylint: enable=bare-except sequence = music_pb2.NoteSequence() # Populate header. sequence.ticks_per_quarter = midi.resolution sequence.source_info.parser = music_pb2.NoteSequence.SourceInfo.PRETTY_MIDI sequence.source_info.encoding_type = ( music_pb2.NoteSequence.SourceInfo.MIDI) # Populate time signatures. for midi_time in midi.time_signature_changes: time_signature = sequence.time_signatures.add() time_signature.time = midi_time.time time_signature.numerator = midi_time.numerator try: # Denominator can be too large for int32. time_signature.denominator = midi_time.denominator except ValueError: raise MIDIConversionError('Invalid time signature denominator %d' % midi_time.denominator) # Populate key signatures. for midi_key in midi.key_signature_changes: key_signature = sequence.key_signatures.add() key_signature.time = midi_key.time key_signature.key = midi_key.key_number % 12 midi_mode = midi_key.key_number / 12 if midi_mode == 0: key_signature.mode = key_signature.MAJOR elif midi_mode == 1: key_signature.mode = key_signature.MINOR else: raise MIDIConversionError('Invalid midi_mode %i' % midi_mode) # Populate tempo changes. tempo_times, tempo_qpms = midi.get_tempo_changes() for time_in_seconds, tempo_in_qpm in zip(tempo_times, tempo_qpms): tempo = sequence.tempos.add() tempo.time = time_in_seconds tempo.qpm = tempo_in_qpm # Populate notes by first gathering them all from the midi's instruments, then # sorting them primarily by start and secondarily by end, and finally looping # through this sorted list and appending each as a new sequence.note. We also # here set the sequence.total_time as the max end time in the notes. # TODO(douglaseck): Eliminate some of this boilerplate code. midi_notes = [] midi_pitch_bends = [] midi_control_changes = [] for num_instrument, midi_instrument in enumerate(midi.instruments): for midi_note in midi_instrument.notes: if not sequence.total_time or midi_note.end > sequence.total_time: sequence.total_time = midi_note.end midi_notes.append((midi_instrument.program, num_instrument, midi_instrument.is_drum, midi_note)) for midi_pitch_bend in midi_instrument.pitch_bends: midi_pitch_bends.append( (midi_instrument.program, num_instrument, midi_instrument.is_drum, midi_pitch_bend)) for midi_control_change in midi_instrument.control_changes: midi_control_changes.append( (midi_instrument.program, num_instrument, midi_instrument.is_drum, midi_control_change)) for program, instrument, is_drum, midi_note in midi_notes: note = sequence.notes.add() note.instrument = instrument note.program = program note.start_time = midi_note.start note.end_time = midi_note.end note.pitch = midi_note.pitch note.velocity = midi_note.velocity note.is_drum = is_drum for program, instrument, is_drum, midi_pitch_bend in midi_pitch_bends: pitch_bend = sequence.pitch_bends.add() pitch_bend.instrument = instrument pitch_bend.program = program pitch_bend.time = midi_pitch_bend.time pitch_bend.bend = midi_pitch_bend.pitch pitch_bend.is_drum = is_drum for program, instrument, is_drum, midi_control_change in midi_control_changes: control_change = sequence.control_changes.add() control_change.instrument = instrument control_change.program = program control_change.time = midi_control_change.time control_change.control_number = midi_control_change.number control_change.control_value = midi_control_change.value control_change.is_drum = is_drum # TODO(douglaseck): Estimate note type (e.g. quarter note) and populate # note.numerator and note.denominator. return sequence def sequence_proto_to_pretty_midi(sequence): """Convert tensorflow.magenta.NoteSequence proto to a PrettyMIDI. Time is stored in the NoteSequence in absolute values (seconds) as opposed to relative values (MIDI ticks). When the NoteSequence is translated back to PrettyMIDI the absolute time is retained. The tempo map is also recreated. Args: sequence: A tensorfow.magenta.NoteSequence proto. Returns: A pretty_midi.PrettyMIDI object or None if sequence could not be decoded. """ kwargs = {} if sequence.tempos and sequence.tempos[0].time == 0: kwargs['initial_tempo'] = sequence.tempos[0].qpm pm = pretty_midi.PrettyMIDI(resolution=sequence.ticks_per_quarter, **kwargs) # Create an empty instrument to contain time and key signatures. instrument = pretty_midi.Instrument(0) pm.instruments.append(instrument) # Populate time signatures. for seq_ts in sequence.time_signatures: time_signature = pretty_midi.containers.TimeSignature( seq_ts.numerator, seq_ts.denominator, seq_ts.time) pm.time_signature_changes.append(time_signature) # Populate key signatures. for seq_key in sequence.key_signatures: key_number = seq_key.key if seq_key.mode == seq_key.MINOR: key_number += _PRETTY_MIDI_MAJOR_TO_MINOR_OFFSET key_signature = pretty_midi.containers.KeySignature( key_number, seq_key.time) pm.key_signature_changes.append(key_signature) # Populate tempo. The first tempo change was done in PrettyMIDI constructor. # TODO(douglaseck): Update this code if pretty_midi adds the ability to # write tempo. if len(sequence.tempos) > 1: for seq_tempo in sequence.tempos[1:]: tick_scale = 60.0 / (pm.resolution * seq_tempo.qpm) tick = pm.time_to_tick(seq_tempo.time) # pylint: disable=protected-access pm._PrettyMIDI__tick_scales.append((tick, tick_scale)) # pylint: enable=protected-access # Populate instrument events by first gathering notes and other event types # in lists then write them sorted to the PrettyMidi object. instrument_events = defaultdict(lambda: defaultdict(list)) for seq_note in sequence.notes: instrument_events[(seq_note.instrument, seq_note.program, seq_note.is_drum)]['notes'].append( pretty_midi.Note( seq_note.velocity, seq_note.pitch, seq_note.start_time, seq_note.end_time)) for seq_bend in sequence.pitch_bends: instrument_events[(seq_bend.instrument, seq_bend.program, seq_bend.is_drum)]['bends'].append( pretty_midi.PitchBend(seq_bend.bend, seq_bend.time)) for seq_cc in sequence.control_changes: instrument_events[(seq_cc.instrument, seq_cc.program, seq_cc.is_drum)]['controls'].append( pretty_midi.ControlChange( seq_cc.control_number, seq_cc.control_value, seq_cc.time)) for (instr_id, prog_id, is_drum) in sorted(instrument_events.keys()): # For instr_id 0 append to the instrument created above. if instr_id > 0: instrument = pretty_midi.Instrument(prog_id, is_drum) pm.instruments.append(instrument) instrument.program = prog_id instrument.notes = instrument_events[ (instr_id, prog_id, is_drum)]['notes'] instrument.pitch_bends = instrument_events[ (instr_id, prog_id, is_drum)]['bends'] instrument.control_changes = instrument_events[ (instr_id, prog_id, is_drum)]['controls'] return pm def midi_file_to_sequence_proto(midi_file): """Converts MIDI file to a tensorflow.magenta.NoteSequence proto. Args: midi_file: A string path to a MIDI file. Returns: A tensorflow.magenta.Sequence proto. Raises: MIDIConversionError: Invalid midi_file. """ with tf.gfile.Open(midi_file, 'r') as f: midi_as_string = f.read() return midi_to_sequence_proto(midi_as_string) def sequence_proto_to_midi_file(sequence, output_file): """Convert tensorflow.magenta.NoteSequence proto to a MIDI file on disk. Time is stored in the NoteSequence in absolute values (seconds) as opposed to relative values (MIDI ticks). When the NoteSequence is translated back to MIDI the absolute time is retained. The tempo map is also recreated. Args: sequence: A tensorfow.magenta.NoteSequence proto. output_file: String path to MIDI file that will be written. """ pretty_midi_object = sequence_proto_to_pretty_midi(sequence) pretty_midi_object.write(output_file)