hifigan_denoiser.py

# SPDX-FileCopyrightText: Copyright (c) 2022 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
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import torch
from audio_processing import STFT


class Denoiser(torch.nn.Module):
    """Removes model bias from audio produced with hifigan"""

    def __init__(
        self, hifigan, filter_length=1024, n_overlap=4, win_length=1024, mode="zeros"
    ):
        super(Denoiser, self).__init__()
        self.stft = STFT(
            filter_length=filter_length,
            hop_length=int(filter_length / n_overlap),
            win_length=win_length,
        )
        self.stft = self.stft.to(hifigan.ups[0].weight.device)
        if mode == "zeros":
            mel_input = torch.zeros(
                (1, 80, 88),
                dtype=hifigan.ups[0].weight.dtype,
                device=hifigan.ups[0].weight.device,
            )
        elif mode == "normal":
            mel_input = torch.randn(
                (1, 80, 88),
                dtype=hifigan.upsample.weight.dtype,
                device=hifigan.upsample.weight.device,
            )
        else:
            raise Exception("Mode {} if not supported".format(mode))

        with torch.no_grad():
            bias_audio = hifigan(mel_input).float()[0]
            bias_spec, _ = self.stft.transform(bias_audio)

        self.register_buffer("bias_spec", bias_spec[:, :, 0][:, :, None])

    def forward(self, audio, strength=0.1):
        audio_spec, audio_angles = self.stft.transform(audio.float())
        audio_spec_denoised = audio_spec - self.bias_spec * strength
        audio_spec_denoised = torch.clamp(audio_spec_denoised, 0.0)
        audio_denoised = self.stft.inverse(audio_spec_denoised, audio_angles)
        return audio_denoised