Computes the inverse modified DCT of mdcts
.
tf.signal.inverse_mdct(
mdcts,
window_fn=tf.signal.vorbis_window
,
norm=None,
name=None
)
To reconstruct an original waveform, the same window function should
be used with mdct
and inverse_mdct
.
Example usage:
@tf.function
def compare_round_trip():
samples = 1000
frame_length = 400
halflen = frame_length // 2
waveform = tf.random.normal(dtype=tf.float32, shape=[samples])
waveform_pad = tf.pad(waveform, [[halflen, 0],])
mdct = tf.signal.mdct(waveform_pad, frame_length, pad_end=True,
window_fn=tf.signal.vorbis_window)
inverse_mdct = tf.signal.inverse_mdct(mdct,
window_fn=tf.signal.vorbis_window)
inverse_mdct = inverse_mdct[halflen: halflen + samples]
return waveform, inverse_mdct
waveform, inverse_mdct = compare_round_trip()
np.allclose(waveform.numpy(), inverse_mdct.numpy(), rtol=1e-3, atol=1e-4)
True
Implemented with TPU/GPU-compatible ops and supports gradients.
Args |
mdcts
|
A float32 /float64 [..., frames, frame_length // 2]
Tensor of MDCT bins representing a batch of frame_length // 2 -point
MDCTs.
|
window_fn
|
A callable that takes a frame_length and a dtype keyword
argument and returns a [frame_length] Tensor of samples in the
provided datatype. If set to None , a rectangular window with a scale of
1/sqrt(2) is used. For perfect reconstruction of a signal from mdct
followed by inverse_mdct , please use tf.signal.vorbis_window ,
tf.signal.kaiser_bessel_derived_window or None . If using another
window function, make sure that w[n]^2 + w[n + frame_length // 2]^2 = 1
and w[n] = w[frame_length - n - 1] for n = 0,...,frame_length // 2 - 1 to
achieve perfect reconstruction.
|
norm
|
If "ortho", orthonormal inverse DCT4 is performed, if it is None,
a regular dct4 followed by scaling of 1/frame_length is performed.
|
name
|
An optional name for the operation.
|
Returns |
A [..., samples] Tensor of float32 /float64 signals representing
the inverse MDCT for each input MDCT in mdcts where samples is
(frames - 1) * (frame_length // 2) + frame_length .
|
Raises |
ValueError
|
If mdcts is not at least rank 2.
|