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52 lines
1.6 KiB
52 lines
1.6 KiB
# Copyright (c) 2020 PaddlePaddle Authors. 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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import math
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import numpy as np
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import paddle
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# x: [0: 2**bit-1], return: [-1, 1]
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def label_2_float(x, bits):
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return 2 * x / (2**bits - 1.) - 1.
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#x: [-1, 1], return: [0, 2**bits-1]
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def float_2_label(x, bits):
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assert abs(x).max() <= 1.0
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x = (x + 1.) * (2**bits - 1) / 2
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return x.clip(0, 2**bits - 1)
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# y: [-1, 1], mu: 2**bits, return: [0, 2**bits-1]
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# see https://en.wikipedia.org/wiki/%CE%9C-law_algorithm
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# be careful the input `mu` here, which is +1 than that of the link above
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def encode_mu_law(x, mu):
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mu = mu - 1
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fx = np.sign(x) * np.log(1 + mu * np.abs(x)) / np.log(1 + mu)
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return np.floor((fx + 1) / 2 * mu + 0.5)
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# from_labels = True:
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# y: [0: 2**bit-1], mu: 2**bits, return: [-1,1]
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# from_labels = False:
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# y: [-1, 1], return: [-1, 1]
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def decode_mu_law(y, mu, from_labels=True):
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# TODO: get rid of log2 - makes no sense
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if from_labels:
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y = label_2_float(y, math.log2(mu))
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mu = mu - 1
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x = paddle.sign(y) / mu * ((1 + mu)**paddle.abs(y) - 1)
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return x
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