#!/usr/bin/env python
# coding: utf8
""" This module provides audio data convertion functions. """
# pylint: disable=import-error
import numpy as np
import tensorflow as tf
# pylint: enable=import-error
from ..utils.tensor import from_float32_to_uint8, from_uint8_to_float32
__email__ = 'research@deezer.com'
__author__ = 'Deezer Research'
__license__ = 'MIT License'
def to_n_channels(waveform, n_channels):
""" Convert a waveform to n_channels by removing or
duplicating channels if needed (in tensorflow).
:param waveform: Waveform to transform.
:param n_channels: Number of channel to reshape waveform in.
:returns: Reshaped waveform.
"""
return tf.cond(
tf.shape(waveform)[1] >= n_channels,
true_fn=lambda: waveform[:, :n_channels],
false_fn=lambda: tf.tile(waveform, [1, n_channels])[:, :n_channels]
)
def to_stereo(waveform):
""" Convert a waveform to stereo by duplicating if mono,
or truncating if too many channels.
:param waveform: a (N, d) numpy array.
:returns: A stereo waveform as a (N, 1) numpy array.
"""
if waveform.shape[1] == 1:
return np.repeat(waveform, 2, axis=-1)
if waveform.shape[1] > 2:
return waveform[:, :2]
return waveform
def gain_to_db(tensor, espilon=10e-10):
""" Convert from gain to decibel in tensorflow.
:param tensor: Tensor to convert.
:param epsilon: Operation constant.
:returns: Converted tensor.
"""
return 20. / np.log(10) * tf.math.log(tf.maximum(tensor, espilon))
def db_to_gain(tensor):
""" Convert from decibel to gain in tensorflow.
:param tensor_db: Tensor to convert.
:returns: Converted tensor.
"""
return tf.pow(10., (tensor / 20.))
def spectrogram_to_db_uint(spectrogram, db_range=100., **kwargs):
""" Encodes given spectrogram into uint8 using decibel scale.
:param spectrogram: Spectrogram to be encoded as TF float tensor.
:param db_range: Range in decibel for encoding.
:returns: Encoded decibel spectrogram as uint8 tensor.
"""
db_spectrogram = gain_to_db(spectrogram)
max_db_spectrogram = tf.reduce_max(db_spectrogram)
db_spectrogram = tf.maximum(db_spectrogram, max_db_spectrogram - db_range)
return from_float32_to_uint8(db_spectrogram, **kwargs)
def db_uint_spectrogram_to_gain(db_uint_spectrogram, min_db, max_db):
""" Decode spectrogram from uint8 decibel scale.
:param db_uint_spectrogram: Decibel pectrogram to decode.
:param min_db: Lower bound limit for decoding.
:param max_db: Upper bound limit for decoding.
:returns: Decoded spectrogram as float2 tensor.
"""
db_spectrogram = from_uint8_to_float32(db_uint_spectrogram, min_db, max_db)
return db_to_gain(db_spectrogram)
