From 3ab8169167eb27cf05347b430171e9ed84f4297c Mon Sep 17 00:00:00 2001
From: moto <855818+mthrok@users.noreply.github.com>
Date: Wed, 18 Mar 2020 09:32:56 -0700
Subject: [PATCH] Use istft from torch

---
 test/common_utils.py     |   8 ++-
 torchaudio/functional.py | 107 +++------------------------------------
 2 files changed, 13 insertions(+), 102 deletions(-)

diff --git a/test/common_utils.py b/test/common_utils.py
index a79f413d2b..3d09cc4697 100644
--- a/test/common_utils.py
+++ b/test/common_utils.py
@@ -1,7 +1,13 @@
 from __future__ import absolute_import, division, print_function, unicode_literals
 import os
 from shutil import copytree
-import backports.tempfile as tempfile
+import platform
+_MAJOR, _MINOR, _PATCH = platform.python_version_tuple()
+if _MAJOR == '2' or (_MAJOR == '3' and int(_MINOR) < 7):
+    import backports.tempfile as tempfile
+else:
+    import tempfile
+
 import torch
 
 TEST_DIR_PATH = os.path.dirname(os.path.realpath(__file__))
diff --git a/torchaudio/functional.py b/torchaudio/functional.py
index c8763ad3c2..08ed03cb3e 100644
--- a/torchaudio/functional.py
+++ b/torchaudio/functional.py
@@ -3,6 +3,7 @@
 from __future__ import absolute_import, division, print_function, unicode_literals
 
 import math
+import warnings
 
 import torch
 
@@ -120,107 +121,11 @@ def istft(
     Returns:
         torch.Tensor: Least squares estimation of the original signal of size (..., signal_length)
     """
-    stft_matrix_dim = stft_matrix.dim()
-    assert 3 <= stft_matrix_dim, "Incorrect stft dimension: %d" % (stft_matrix_dim)
-    assert stft_matrix.numel() > 0
-
-    if stft_matrix_dim == 3:
-        # add a channel dimension
-        stft_matrix = stft_matrix.unsqueeze(0)
-
-    # pack batch
-    shape = stft_matrix.size()
-    stft_matrix = stft_matrix.view(-1, shape[-3], shape[-2], shape[-1])
-
-    dtype = stft_matrix.dtype
-    device = stft_matrix.device
-    fft_size = stft_matrix.size(1)
-    assert (onesided and n_fft // 2 + 1 == fft_size) or (
-        not onesided and n_fft == fft_size
-    ), (
-        "one_sided implies that n_fft // 2 + 1 == fft_size and not one_sided implies n_fft == fft_size. "
-        + "Given values were onesided: %s, n_fft: %d, fft_size: %d"
-        % ("True" if onesided else False, n_fft, fft_size)
-    )
-
-    # use stft defaults for Optionals
-    if win_length is None:
-        win_length = n_fft
-
-    if hop_length is None:
-        hop_length = int(win_length // 4)
-
-    # There must be overlap
-    assert 0 < hop_length <= win_length
-    assert 0 < win_length <= n_fft
-
-    if window is None:
-        window = torch.ones(win_length, device=device, dtype=dtype)
-
-    assert window.dim() == 1 and window.size(0) == win_length
-
-    if win_length != n_fft:
-        # center window with pad left and right zeros
-        left = (n_fft - win_length) // 2
-        window = torch.nn.functional.pad(window, (left, n_fft - win_length - left))
-        assert window.size(0) == n_fft
-    # win_length and n_fft are synonymous from here on
-
-    stft_matrix = stft_matrix.transpose(1, 2)  # size (channel, n_frame, fft_size, 2)
-    stft_matrix = torch.irfft(
-        stft_matrix, 1, normalized, onesided, signal_sizes=(n_fft,)
-    )  # size (channel, n_frame, n_fft)
-
-    assert stft_matrix.size(2) == n_fft
-    n_frame = stft_matrix.size(1)
-
-    ytmp = stft_matrix * window.view(1, 1, n_fft)  # size (channel, n_frame, n_fft)
-    # each column of a channel is a frame which needs to be overlap added at the right place
-    ytmp = ytmp.transpose(1, 2)  # size (channel, n_fft, n_frame)
-
-    eye = torch.eye(n_fft, device=device, dtype=dtype).unsqueeze(1)  # size (n_fft, 1, n_fft)
-
-    # this does overlap add where the frames of ytmp are added such that the i'th frame of
-    # ytmp is added starting at i*hop_length in the output
-    y = torch.nn.functional.conv_transpose1d(
-        ytmp, eye, stride=hop_length, padding=0
-    )  # size (channel, 1, expected_signal_len)
-
-    # do the same for the window function
-    window_sq = (
-        window.pow(2).view(n_fft, 1).repeat((1, n_frame)).unsqueeze(0)
-    )  # size (1, n_fft, n_frame)
-    window_envelop = torch.nn.functional.conv_transpose1d(
-        window_sq, eye, stride=hop_length, padding=0
-    )  # size (1, 1, expected_signal_len)
-
-    expected_signal_len = n_fft + hop_length * (n_frame - 1)
-    assert y.size(2) == expected_signal_len
-    assert window_envelop.size(2) == expected_signal_len
-
-    half_n_fft = n_fft // 2
-    # we need to trim the front padding away if center
-    start = half_n_fft if center else 0
-    end = -half_n_fft if length is None else start + length
-
-    y = y[:, :, start:end]
-    window_envelop = window_envelop[:, :, start:end]
-
-    # check NOLA non-zero overlap condition
-    window_envelop_lowest = window_envelop.abs().min()
-    assert window_envelop_lowest > 1e-11, "window overlap add min: %f" % (
-        window_envelop_lowest
-    )
-
-    y = (y / window_envelop).squeeze(1)  # size (channel, expected_signal_len)
-
-    # unpack batch
-    y = y.view(shape[:-3] + y.shape[-1:])
-
-    if stft_matrix_dim == 3:  # remove the channel dimension
-        y = y.squeeze(0)
-
-    return y
+    warnings.warn(
+        'istft has been moved to PyTorch and will be deprecated, please use torch.istft instead.')
+    return torch.istft(
+        input=stft_matrix, n_fft=n_fft, hop_length=hop_length, win_length=win_length, window=window,
+        center=center, pad_mode=pad_mode, normalized=normalized, onesided=onesided, length=length)
 
 
 def spectrogram(