torchaudio.transforms

torchaudio.transforms module contains common audio processings and feature extractions. The following diagram shows the relationship between some of the available transforms.

Transforms are implemented using torch.nn.Module. Common ways to build a processing pipeline are to define custom Module class or chain Modules together using torch.nn.Sequential, then move it to a target device and data type.

# Define custom feature extraction pipeline.
#
# 1. Resample audio
# 2. Convert to power spectrogram
# 3. Apply augmentations
# 4. Convert to mel-scale
#
class MyPipeline(torch.nn.Module):
    def __init__(
        self,
        input_freq=16000,
        resample_freq=8000,
        n_fft=1024,
        n_mel=256,
        stretch_factor=0.8,
    ):
        super().__init__()
        self.resample = Resample(orig_freq=input_freq, new_freq=resample_freq)

        self.spec = Spectrogram(n_fft=n_fft, power=2)

        self.spec_aug = torch.nn.Sequential(
            TimeStretch(stretch_factor, fixed_rate=True),
            FrequencyMasking(freq_mask_param=80),
            TimeMasking(time_mask_param=80),
        )

        self.mel_scale = MelScale(
            n_mels=n_mel, sample_rate=resample_freq, n_stft=n_fft // 2 + 1)

    def forward(self, waveform: torch.Tensor) -> torch.Tensor:
        # Resample the input
        resampled = self.resample(waveform)

        # Convert to power spectrogram
        spec = self.spec(resampled)

        # Apply SpecAugment
        spec = self.spec_aug(spec)

        # Convert to mel-scale
        mel = self.mel_scale(spec)

        return mel

# Instantiate a pipeline
pipeline = MyPipeline()

# Move the computation graph to CUDA
pipeline.to(device=torch.device("cuda"), dtype=torch.float32)

# Perform the transform
features = pipeline(waveform)

Please check out tutorials that cover in-depth usage of trasforms.

Audio Feature Extractions

Audio Feature Extractions

Utility

AmplitudeToDB	Turn a tensor from the power/amplitude scale to the decibel scale.
MelScale	Turn a normal STFT into a mel frequency STFT with triangular filter banks.
InverseMelScale	Estimate a STFT in normal frequency domain from mel frequency domain.
MuLawEncoding	Encode signal based on mu-law companding.
MuLawDecoding	Decode mu-law encoded signal.
Resample	Resample a signal from one frequency to another.
Fade	Add a fade in and/or fade out to an waveform.
Vol	Adjust volume of waveform.
Loudness	Measure audio loudness according to the ITU-R BS.1770-4 recommendation.

Feature Extractions

Spectrogram	Create a spectrogram from a audio signal.
InverseSpectrogram	Create an inverse spectrogram to recover an audio signal from a spectrogram.
MelSpectrogram	Create MelSpectrogram for a raw audio signal.
GriffinLim	Compute waveform from a linear scale magnitude spectrogram using the Griffin-Lim transformation.
MFCC	Create the Mel-frequency cepstrum coefficients from an audio signal.
LFCC	Create the linear-frequency cepstrum coefficients from an audio signal.
ComputeDeltas	Compute delta coefficients of a tensor, usually a spectrogram.
PitchShift	Shift the pitch of a waveform by n_steps steps.
SlidingWindowCmn	Apply sliding-window cepstral mean (and optionally variance) normalization per utterance.
SpectralCentroid	Compute the spectral centroid for each channel along the time axis.
Vad	Voice Activity Detector.

Augmentations

The following transforms implement popular augmentation techniques known as SpecAugment [Park et al., 2019].

FrequencyMasking	Apply masking to a spectrogram in the frequency domain.
TimeMasking	Apply masking to a spectrogram in the time domain.
TimeStretch	Stretch stft in time without modifying pitch for a given rate.

Loss

RNNTLoss

Compute the RNN Transducer loss from Sequence Transduction with Recurrent Neural Networks [Graves, 2012].

Multi-channel

PSD	Compute cross-channel power spectral density (PSD) matrix.
MVDR	Minimum Variance Distortionless Response (MVDR) module that performs MVDR beamforming with Time-Frequency masks.
RTFMVDR	Minimum Variance Distortionless Response (MVDR [Capon, 1969]) module based on the relative transfer function (RTF) and power spectral density (PSD) matrix of noise.
SoudenMVDR	Minimum Variance Distortionless Response (MVDR [Capon, 1969]) module based on the method proposed by Souden et, al. [Souden et al., 2009].