133 lines
4.6 KiB
Python
133 lines
4.6 KiB
Python
# Copyright 2016 Google Inc. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""A MelodyEncoderDecoder specific to the basic RNN model."""
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# internal imports
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from magenta.music import constants
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from magenta.music import melodies_lib
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NUM_SPECIAL_MELODY_EVENTS = constants.NUM_SPECIAL_MELODY_EVENTS
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MIN_NOTE = 48 # Inclusive
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MAX_NOTE = 84 # Exclusive
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TRANSPOSE_TO_KEY = 0 # C Major
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class MelodyEncoderDecoder(melodies_lib.MelodyEncoderDecoder):
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"""A MelodyEncoderDecoder specific to the lookback RNN model.
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Attributes:
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_num_model_events: The number of different melody events that can be
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generated by this model.
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"""
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def __init__(self):
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"""Initializes the MelodyEncoderDecoder."""
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super(MelodyEncoderDecoder, self).__init__(MIN_NOTE, MAX_NOTE,
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TRANSPOSE_TO_KEY)
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self._num_model_events = (self.max_note - self.min_note +
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NUM_SPECIAL_MELODY_EVENTS)
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@property
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def input_size(self):
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return self._num_model_events
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@property
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def num_classes(self):
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return self._num_model_events
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def melody_event_to_model_event(self, melody_event):
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"""Collapses a melody event value into a zero-based index range.
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Args:
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melody_event: A MonophonicMelody event value. -2 = no event,
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-1 = note-off event, [0, 127] = note-on event for that midi pitch.
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Returns:
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An int in the range [0, self._num_model_events). 0 = no event,
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1 = note-off event, [2, self._num_model_events) = note-on event for
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that pitch relative to the [self._min_note, self._max_note) range.
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"""
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if melody_event < 0:
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return melody_event + NUM_SPECIAL_MELODY_EVENTS
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return melody_event - self.min_note + NUM_SPECIAL_MELODY_EVENTS
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def model_event_to_melody_event(self, model_event):
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"""Expands a zero-based index value to its equivalent melody event value.
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Args:
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model_event: An int in the range [0, self._num_model_events).
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0 = no event, 1 = note-off event,
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[2, self._num_model_events) = note-on event for that pitch relative
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to the [self._min_note, self._max_note) range.
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Returns:
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A MonophonicMelody event value. -2 = no event, -1 = note-off event,
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[0, 127] = note-on event for that midi pitch.
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"""
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if model_event < NUM_SPECIAL_MELODY_EVENTS:
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return model_event - NUM_SPECIAL_MELODY_EVENTS
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return model_event - NUM_SPECIAL_MELODY_EVENTS + self.min_note
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def events_to_input(self, events, position):
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"""Returns the input vector for the given position in the melody.
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Returns a one-hot vector for the given position in the melody mapped to the
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model's event range. 0 = no event, 1 = note-off event,
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[2, self._num_model_events) = note-on event for that pitch relative to the
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[self._min_note, self._max_note) range.
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Args:
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events: A MonophonicMelody object.
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position: An integer event position in the melody.
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Returns:
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An input vector, a list of floats.
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"""
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input_ = [0.0] * self.input_size
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input_[self.melody_event_to_model_event(events[position])] = 1.0
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return input_
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def events_to_label(self, events, position):
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"""Returns the label for the given position in the melody.
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Returns the zero-based index value for the given position in the melody
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mapped to the model's event range. 0 = no event, 1 = note-off event,
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[2, self._num_model_events) = note-on event for that pitch relative to the
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[self._min_note, self._max_note) range.
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Args:
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events: A MonophonicMelody object.
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position: An integer event position in the melody.
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Returns:
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A label, an integer.
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"""
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return self.melody_event_to_model_event(events[position])
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def class_index_to_event(self, class_index, events):
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"""Returns the melody event for the given class index.
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This is the reverse process of the self.melody_to_label method.
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Args:
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class_index: An integer in the range [0, self.num_classes).
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events: A MonophonicMelody object. This object is not used in this
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implementation.
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Returns:
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A MonophonicMelody event value.
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"""
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return self.model_event_to_melody_event(class_index)
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