Update spectrogram to use complex

torchaudio/functional/functional.py

@@ -47,7 +47,8 @@ def spectrogram(
         normalized: bool,
         center: bool = True,
         pad_mode: str = "reflect",
-        onesided: bool = True
+        onesided: bool = True,
+        return_complex: bool = False,
 ) -> Tensor:
     r"""Create a spectrogram or a batch of spectrograms from a raw audio signal.
     The spectrogram can be either magnitude-only or complex.
@@ -70,12 +71,22 @@ def spectrogram(
             :attr:`center` is ``True``. Default: ``"reflect"``
         onesided (bool, optional): controls whether to return half of results to
             avoid redundancy. Default: ``True``
+        return_complex (bool, optional):
+            ``return_complex = True``, this function returns the resulting Tensor in
+            complex dtype, otherwise it returns the resulting Tensor in real dtype with extra
+            dimension for real and imaginary parts. (see ``torch.view_as_real``).
+            When ``power`` is provided, the value must be False, as the resulting
+            Tensor represents real-valued power.
 
     Returns:
         Tensor: Dimension (..., freq, time), freq is
         ``n_fft // 2 + 1`` and ``n_fft`` is the number of
         Fourier bins, and time is the number of window hops (n_frame).
     """
+    if power is not None and return_complex:
+        raise ValueError(
+            'When `power` is provided, the return value is real-valued. '
+            'Therefore, `return_complex` must be False.')
 
     if pad > 0:
         # TODO add "with torch.no_grad():" back when JIT supports it
@@ -108,7 +119,9 @@ def spectrogram(
         if power == 1.0:
             return spec_f.abs()
         return spec_f.abs().pow(power)
-    return torch.view_as_real(spec_f)
+    if not return_complex:
+        return torch.view_as_real(spec_f)
+    return spec_f
 
 
 def griffinlim(

torchaudio/transforms.py

@@ -53,6 +53,12 @@ class Spectrogram(torch.nn.Module):
             :attr:`center` is ``True``. Default: ``"reflect"``
         onesided (bool, optional): controls whether to return half of results to
             avoid redundancy Default: ``True``
+        return_complex (bool, optional):
+            ``return_complex = True``, this function returns the resulting Tensor in
+            complex dtype, otherwise it returns the resulting Tensor in real dtype with extra
+            dimension for real and imaginary parts. (see ``torch.view_as_real``).
+            When ``power`` is provided, the value must be False, as the resulting
+            Tensor represents real-valued power.
     """
     __constants__ = ['n_fft', 'win_length', 'hop_length', 'pad', 'power', 'normalized']
 
@@ -67,7 +73,8 @@ def __init__(self,
                  wkwargs: Optional[dict] = None,
                  center: bool = True,
                  pad_mode: str = "reflect",
-                 onesided: bool = True) -> None:
+                 onesided: bool = True,
+                 return_complex: bool = False) -> None:
         super(Spectrogram, self).__init__()
         self.n_fft = n_fft
         # number of FFT bins. the returned STFT result will have n_fft // 2 + 1
@@ -82,6 +89,7 @@ def __init__(self,
         self.center = center
         self.pad_mode = pad_mode
         self.onesided = onesided
+        self.return_complex = return_complex
 
     def forward(self, waveform: Tensor) -> Tensor:
         r"""
@@ -104,7 +112,8 @@ def forward(self, waveform: Tensor) -> Tensor:
             self.normalized,
             self.center,
             self.pad_mode,
-            self.onesided
+            self.onesided,
+            self.return_complex,
         )
 
 
@@ -457,7 +466,8 @@ def __init__(self,
                  pad_mode: str = "reflect",
                  onesided: bool = True,
                  norm: Optional[str] = None,
-                 mel_scale: str = "htk") -> None:
+                 mel_scale: str = "htk",
+                 return_complex: bool = False) -> None:
         super(MelSpectrogram, self).__init__()
         self.sample_rate = sample_rate
         self.n_fft = n_fft
@@ -469,11 +479,20 @@ def __init__(self,
         self.n_mels = n_mels  # number of mel frequency bins
         self.f_max = f_max
         self.f_min = f_min
-        self.spectrogram = Spectrogram(n_fft=self.n_fft, win_length=self.win_length,
-                                       hop_length=self.hop_length,
-                                       pad=self.pad, window_fn=window_fn, power=self.power,
-                                       normalized=self.normalized, wkwargs=wkwargs,
-                                       center=center, pad_mode=pad_mode, onesided=onesided)
+        self.spectrogram = Spectrogram(
+            n_fft=self.n_fft,
+            win_length=self.win_length,
+            hop_length=self.hop_length,
+            pad=self.pad,
+            window_fn=window_fn,
+            power=self.power,
+            normalized=self.normalized,
+            wkwargs=wkwargs,
+            center=center,
+            pad_mode=pad_mode,
+            onesided=onesided,
+            return_complex=return_complex,
+        )
         self.mel_scale = MelScale(
             self.n_mels,
             self.sample_rate,