Update calls to torch.stft to have return_complex=True

[mthrok]

Resolves #1095

[mruberry]

Thank you, @mthrok!

[peterbell10]

Since the plan is to deprecate return_complex=False, you may want to go to torch.view_as_real(torch.stft(..., return_complex=True)).

[mruberry]

That's a good future proofing idea, @peterbell10, but I suggest we just go with the simpler and smaller change for the moment and revisit how torchaudio wants to handle complex numbers for the 1.9 release. Maybe torchaudio will want to switch to using complex tensors.

[peterbell10]

Not sure I understand. view_as_real is the exact same data format as return_complex=False, so it doesn't require any further changes. It just avoids the warning.

[mruberry]

Oh you're right, thank you. I forgot we're also putting a warning on this. It's been a long day...

Sorry @mthrok, I was mistaken. We should take @peterbell10's recommendation to use torch.view_as_real(torch.stft(..., return_complex=True)) because this will avoid a warning, since we're also deprecating return_complex=False for the 1.8 release.

[mthrok]

@peterbell10 @mruberry Update the PR to use return_complex=True + view_as_real. Review please.

[mruberry]

This looks great. Thank you again @mthrok and @peterbell10!