Update on "Use new FFT operators in stft"

Fixes #42175 (comment)




[ghstack-poisoned]

aten/src/ATen/native/SpectralOps.cpp

@@ -771,6 +771,11 @@ Tensor istft(const Tensor& self, const int64_t n_fft, const optional<int64_t> ho
   const auto hop_length = hop_lengthOpt.value_or(n_fft >> 2);
   const auto win_length = win_lengthOpt.value_or(n_fft);
 
+  if (!self.is_complex()) {
+    TORCH_WARN_ONCE(
+      "istft will require a complex-valued input tensor in a future PyTorch release. "
+      "Matching the output from stft with return_complex=True. ");
+  }
   Tensor input = self.is_complex() ? at::view_as_real(self) : self;
   const auto input_dim = input.dim();
   const auto n_frames = input.size(-2);

torch/functional.py

@@ -618,6 +618,10 @@ def istft(input: Tensor, n_fft: int, hop_length: Optional[int] = None,
             can either be complex (``channel``, ``fft_size``, ``n_frame``), or real
             (``channel``, ``fft_size``, ``n_frame``, 2) where the ``channel``
             dimension is optional.
+
+            .. deprecated:: 1.8.0
+               Real input is deprecated, use complex inputs as returned by
+               ``stft(..., return_complex=True)`` instead.
         n_fft (int): Size of Fourier transform
         hop_length (Optional[int]): The distance between neighboring sliding window frames.
             (Default: ``n_fft // 4``)