From 88d31426f5107005ff01cb5982cd237bf3f1fb39 Mon Sep 17 00:00:00 2001
From: Brian White <bpw@fb.com>
Date: Wed, 19 May 2021 13:14:11 +0100
Subject: [PATCH 1/3] [#1511] Add deprecation warning to MelScale for unset
 weight

Issue a warning if `n_stft` is unitialized or zero in construction.

https://github.com/pytorch/audio/issues/1511
---
 .../transforms/transforms_test_impl.py        | 20 ++++++++++++++++++-
 torchaudio/transforms.py                      |  9 +++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/test/torchaudio_unittest/transforms/transforms_test_impl.py b/test/torchaudio_unittest/transforms/transforms_test_impl.py
index 8a92662200..44f254e540 100644
--- a/test/torchaudio_unittest/transforms/transforms_test_impl.py
+++ b/test/torchaudio_unittest/transforms/transforms_test_impl.py
@@ -1,3 +1,5 @@
+import warnings
+
 import torch
 import torchaudio.transforms as T
 
@@ -39,7 +41,7 @@ def test_InverseMelScale(self):
             get_whitenoise(sample_rate=sample_rate, duration=1, n_channels=2),
             n_fft=n_fft, power=power).to(self.device, self.dtype)
         input = T.MelScale(
-            n_mels=n_mels, sample_rate=sample_rate
+            n_mels=n_mels, sample_rate=sample_rate, n_stft=n_stft
         ).to(self.device, self.dtype)(expected)
 
         # Run transform
@@ -59,3 +61,19 @@ def test_InverseMelScale(self):
         assert _get_ratio(relative_diff < 1e-1) > 0.2
         assert _get_ratio(relative_diff < 1e-3) > 5e-3
         assert _get_ratio(relative_diff < 1e-5) > 1e-5
+
+    def test_melscale_unset_weight_warning(self):
+        """Issue a warning if MelScale initialized without a weight
+
+        As part of the deprecation of lazy intialization behavior (#1510),
+        issue a warning if `n_stft` is not set.
+        """
+        with warnings.catch_warnings(record=True) as caught_warnings:
+            warnings.simplefilter("always")
+            T.MelScale(n_mels=64, sample_rate=8000)
+        assert len(caught_warnings) == 1
+
+        with warnings.catch_warnings(record=True) as caught_warnings:
+            warnings.simplefilter("always")
+            T.MelScale(n_mels=64, sample_rate=8000, n_stft=201)
+        assert len(caught_warnings) == 0
diff --git a/torchaudio/transforms.py b/torchaudio/transforms.py
index 4704c4eb39..b14b3b93ad 100644
--- a/torchaudio/transforms.py
+++ b/torchaudio/transforms.py
@@ -283,6 +283,15 @@ def __init__(self,
 
         assert f_min <= self.f_max, 'Require f_min: {} < f_max: {}'.format(f_min, self.f_max)
 
+        if n_stft is None or n_stft == 0:
+            warnings.warn(
+                'Initialization of torchaudio.transforms.MelScale with an unset weight '
+                '`n_stft` is deprecated and will be removed from a future release. '
+                'Please set a proper n_stftvalue. Typically this isn_fft // 2 + 1. '
+                'Refer to https://github.com/pytorch/audio/issues/1510 '
+                'for more details.'
+            )
+
         fb = torch.empty(0) if n_stft is None else F.create_fb_matrix(
             n_stft, self.f_min, self.f_max, self.n_mels, self.sample_rate, self.norm,
             self.mel_scale)

From 7175f88705e40cee5b91b29d938293e8b70e50aa Mon Sep 17 00:00:00 2001
From: Brian White <brian@dogg.ie>
Date: Wed, 19 May 2021 17:53:58 +0100
Subject: [PATCH 2/3] Update torchaudio/transforms.py

Co-authored-by: moto <855818+mthrok@users.noreply.github.com>
---
 torchaudio/transforms.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/torchaudio/transforms.py b/torchaudio/transforms.py
index b14b3b93ad..2749be2132 100644
--- a/torchaudio/transforms.py
+++ b/torchaudio/transforms.py
@@ -287,7 +287,7 @@ def __init__(self,
             warnings.warn(
                 'Initialization of torchaudio.transforms.MelScale with an unset weight '
                 '`n_stft` is deprecated and will be removed from a future release. '
-                'Please set a proper n_stftvalue. Typically this isn_fft // 2 + 1. '
+                'Please set a proper `n_stft` value. Typically this is `n_fft // 2 + 1`. '
                 'Refer to https://github.com/pytorch/audio/issues/1510 '
                 'for more details.'
             )

From fd15a50c1e8ebbd7863218a1448c3d71ab47d0b7 Mon Sep 17 00:00:00 2001
From: Brian White <brian@dogg.ie>
Date: Wed, 19 May 2021 17:54:09 +0100
Subject: [PATCH 3/3] Update torchaudio/transforms.py

Co-authored-by: moto <855818+mthrok@users.noreply.github.com>
---
 torchaudio/transforms.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/torchaudio/transforms.py b/torchaudio/transforms.py
index 2749be2132..66faa0d753 100644
--- a/torchaudio/transforms.py
+++ b/torchaudio/transforms.py
@@ -286,7 +286,7 @@ def __init__(self,
         if n_stft is None or n_stft == 0:
             warnings.warn(
                 'Initialization of torchaudio.transforms.MelScale with an unset weight '
-                '`n_stft` is deprecated and will be removed from a future release. '
+                '`n_stft=None` is deprecated and will be removed from a future release. '
                 'Please set a proper `n_stft` value. Typically this is `n_fft // 2 + 1`. '
                 'Refer to https://github.com/pytorch/audio/issues/1510 '
                 'for more details.'