#!/usr/bin/env python
'''Time features'''
import numpy as np
from librosa import get_duration
from .base import FeatureExtractor
from ._utils import to_dtype
__all__ = ['TimePosition']
class TimePosition(FeatureExtractor):
'''TimePosition: encode frame position as features.
Attributes
----------
name : str
The name of this feature extractor
sr : number > 0
The sampling rate of audio
hop_length : int > 0
The hop length of analysis windows
'''
def __init__(self, name, sr, hop_length, conv=None, dtype='float32'):
super(TimePosition, self).__init__(name, sr, hop_length, conv=conv,
dtype=dtype)
self.register('relative', 2, self.dtype)
self.register('absolute', 2, self.dtype)
def transform_audio(self, y):
'''Compute the time position encoding
Parameters
----------
y : np.ndarray
Audio buffer
Returns
-------
data : dict
data['relative'] = np.ndarray, shape=(n_frames, 2)
data['absolute'] = np.ndarray, shape=(n_frames, 2)
Relative and absolute time positional encodings.
'''
duration = get_duration(y=y, sr=self.sr)
n_frames = self.n_frames(duration)
relative = np.zeros((n_frames, 2), dtype=np.float32)
relative[:, 0] = np.cos(np.pi * np.linspace(0, 1, num=n_frames))
relative[:, 1] = np.sin(np.pi * np.linspace(0, 1, num=n_frames))
absolute = relative * np.sqrt(duration)
return {'relative': to_dtype(relative[self.idx], self.dtype),
'absolute': to_dtype(absolute[self.idx], self.dtype)}
