Abstract base classes

This section documents the abstract base classes at the top of the inheritance tree in shennong.

Base processor

Base classes for all shennong components

class shennong.base.BaseProcessor[source]

Bases: object

Base class for all processors in shennong

Notes

All processors should specify all the parameters that can be set at the class level in their __init__ as explicit keyword arguments (no *args or **kwargs).

The methods get_params() and set_params() are adapted from sklearn.base.BaseEstimator

get_params(deep=True)[source]

Get parameters for this processor.

Parameters

deep (boolean, optional) – If True, will return the parameters for this processor and contained subobjects that are processors. Default to True.

Returns

params (mapping of string to any) – Parameter names mapped to their values.

set_params(**params)[source]

Set the parameters of this processor.

Returns

self

Raises

ValueError – If any given parameter in params is invalid for the processor.

Base features processor

This module implements the speech features extraction models (processors)

A speech features processor takes an audio signal as input and output features:

Audio –> FeaturesProcessor –> Features

class shennong.features.processor.base.FeaturesProcessor[source]

Bases: shennong.base.BaseProcessor

Base class of all the features extraction models

abstract property name

Name of the processor

abstract property ndims

Dimension of the output features frames

get_properties()[source]

Return the processors properties as a dictionary

abstract process(signal)[source]

Returns features processed from an input signal

Parameters

signal (:class`~shennong.audio.Audio`) – The input audio signal to process features on

Returns

features (Features) – The computed features

process_all(signals, njobs=None)[source]

Returns features processed from several input signals

This function processes the features in parallel jobs.

Parameters

  • signals (dict of :class`~shennong.audio.Audio`) – A dictionnary of input audio signals to process features on, where the keys are item names and values are audio signals.

  • njobs (int, optional) – The number of parallel jobs to run in background. Default to the number of CPU cores available on the machine.

Returns

features (FeaturesCollection) – The computed features on each input signal. The keys of output features are the keys of the input signals.

Raises

ValueError – If the njobs parameter is <= 0

get_params(deep=True)

Get parameters for this processor.

Parameters

deep (boolean, optional) – If True, will return the parameters for this processor and contained subobjects that are processors. Default to True.

Returns

params (mapping of string to any) – Parameter names mapped to their values.

set_params(**params)

Set the parameters of this processor.

Returns

self

Raises

ValueError – If any given parameter in params is invalid for the processor.

class shennong.features.processor.base.FramesProcessor(sample_rate=16000, frame_shift=0.01, frame_length=0.025, dither=1.0, preemph_coeff=0.97, remove_dc_offset=True, window_type='povey', round_to_power_of_two=True, blackman_coeff=0.42, snip_edges=True)[source]

Bases: shennong.features.processor.base.FeaturesProcessor

A base class for frame based features processors.

Wrap the kaldi frames implementation. See [kaldi-frame].

References

kaldi-frame

http://kaldi-asr.org/doc/structkaldi_1_1FrameExtractionOptions.html

property sample_rate

Waveform sample frequency in Hertz

Must match the sample rate of the signal specified in process

property frame_shift

Frame shift in seconds

property frame_length

Frame length in seconds

property dither

Amount of dithering

0.0 means no dither

property preemph_coeff

Coefficient for use in signal preemphasis

get_params(deep=True)

Get parameters for this processor.

Parameters

deep (boolean, optional) – If True, will return the parameters for this processor and contained subobjects that are processors. Default to True.

Returns

params (mapping of string to any) – Parameter names mapped to their values.

get_properties()

Return the processors properties as a dictionary

abstract property name

Name of the processor

abstract property ndims

Dimension of the output features frames

abstract process(signal)

Returns features processed from an input signal

Parameters

signal (:class`~shennong.audio.Audio`) – The input audio signal to process features on

Returns

features (Features) – The computed features

process_all(signals, njobs=None)

Returns features processed from several input signals

This function processes the features in parallel jobs.

Parameters

  • signals (dict of :class`~shennong.audio.Audio`) – A dictionnary of input audio signals to process features on, where the keys are item names and values are audio signals.

  • njobs (int, optional) – The number of parallel jobs to run in background. Default to the number of CPU cores available on the machine.

Returns

features (FeaturesCollection) – The computed features on each input signal. The keys of output features are the keys of the input signals.

Raises

ValueError – If the njobs parameter is <= 0

property remove_dc_offset

If True, subtract mean from waveform on each frame

set_params(**params)

Set the parameters of this processor.

Returns

self

Raises

ValueError – If any given parameter in params is invalid for the processor.

property window_type

Type of window

Must be ‘hamming’, ‘hanning’, ‘povey’, ‘rectangular’ or ‘blackman’

property round_to_power_of_two

If true, round window size to power of two

This is done by zero-padding input to FFT

property blackman_coeff

Constant coefficient for generalized Blackman window

Used only if window_type is ‘blackman’

property snip_edges

If true, output only frames that completely fit in the file

When True the number of frames depends on the frame_length. If False, the number of frames depends only on the frame_shift, and we reflect the data at the ends.

times(nframes)[source]

Returns the times label for the rows given by process()

class shennong.features.processor.base.MelFeaturesProcessor(sample_rate=16000, frame_shift=0.01, frame_length=0.025, dither=1.0, preemph_coeff=0.97, remove_dc_offset=True, window_type='povey', round_to_power_of_two=True, blackman_coeff=0.42, snip_edges=True, num_bins=23, low_freq=20, high_freq=0, vtln_low=100, vtln_high=- 500)[source]

Bases: shennong.features.processor.base.FramesProcessor

A base class for mel-based features processors

The mel-based features are MFCC, PLP and filterbanks. The class implement common options for processing those features. See [kaldi-mel] and [kaldi-frame-2].

References

kaldi-frame-2

http://kaldi-asr.org/doc/structkaldi_1_1FrameExtractionOptions.html

kaldi-mel

http://kaldi-asr.org/doc/structkaldi_1_1MelBanksOptions.html

property blackman_coeff

Constant coefficient for generalized Blackman window

Used only if window_type is ‘blackman’

property dither

Amount of dithering

0.0 means no dither

property frame_length

Frame length in seconds

property frame_shift

Frame shift in seconds

get_params(deep=True)

Get parameters for this processor.

Parameters

deep (boolean, optional) – If True, will return the parameters for this processor and contained subobjects that are processors. Default to True.

Returns

params (mapping of string to any) – Parameter names mapped to their values.

get_properties()

Return the processors properties as a dictionary

abstract property name

Name of the processor

abstract property ndims

Dimension of the output features frames

property preemph_coeff

Coefficient for use in signal preemphasis

process_all(signals, njobs=None)

Returns features processed from several input signals

This function processes the features in parallel jobs.

Parameters

  • signals (dict of :class`~shennong.audio.Audio`) – A dictionnary of input audio signals to process features on, where the keys are item names and values are audio signals.

  • njobs (int, optional) – The number of parallel jobs to run in background. Default to the number of CPU cores available on the machine.

Returns

features (FeaturesCollection) – The computed features on each input signal. The keys of output features are the keys of the input signals.

Raises

ValueError – If the njobs parameter is <= 0

property remove_dc_offset

If True, subtract mean from waveform on each frame

property round_to_power_of_two

If true, round window size to power of two

This is done by zero-padding input to FFT

property sample_rate

Waveform sample frequency in Hertz

Must match the sample rate of the signal specified in process

set_params(**params)

Set the parameters of this processor.

Returns

self

Raises

ValueError – If any given parameter in params is invalid for the processor.

property snip_edges

If true, output only frames that completely fit in the file

When True the number of frames depends on the frame_length. If False, the number of frames depends only on the frame_shift, and we reflect the data at the ends.

times(nframes)

Returns the times label for the rows given by process()

property window_type

Type of window

Must be ‘hamming’, ‘hanning’, ‘povey’, ‘rectangular’ or ‘blackman’

property num_bins

Number of triangular mel-frequency bins

The minimal number of bins is 3

property low_freq

Low cutoff frequency for mel bins in Hertz

property high_freq

High cutoff frequency for mel bins in Hertz

If high_freq < 0, offset from the Nyquist frequency

property vtln_low

Low inflection point in piecewise linear VTLN warping function

In Hertz

property vtln_high

High inflection point in piecewise linear VTLN warping function

In Hertz. If vtln_high < 0, offset from high_freq

process(signal, vtln_warp=1.0)[source]

Compute features with the specified options

Do an optional feature-level vocal tract length normalization (VTLN) when vtln_warp != 1.0.

Parameters

  • signal (Audio, shape = [nsamples, 1]) – The input audio signal to compute the features on, must be mono

  • vtln_warp (float, optional) – The VTLN warping factor to be applied when computing features. Be 1.0 by default, meaning no warping is to be done.

Returns

features (Features, shape = [nframes, ndims]) – The computed features, output will have as many rows as there are frames (depends on the specified options frame_shift and frame_length).

Raises

ValueError – If the input signal has more than one channel (i.e. is not mono). If sample_rate != signal.sample_rate.

Base features post-processor

A post-processor takes features as input and output new features:

Features –> FeaturesPostProcessor –> Features

class shennong.features.postprocessor.base.FeaturesPostProcessor[source]

Bases: shennong.features.processor.base.FeaturesProcessor

abstract process(features)[source]

Returns features post-processed from input features

get_properties(features)[source]

Return the processors properties as a dictionary

get_params(deep=True)

Get parameters for this processor.

Parameters

deep (boolean, optional) – If True, will return the parameters for this processor and contained subobjects that are processors. Default to True.

Returns

params (mapping of string to any) – Parameter names mapped to their values.

abstract property name

Name of the processor

abstract property ndims

Dimension of the output features frames

process_all(signals, njobs=None)

Returns features processed from several input signals

This function processes the features in parallel jobs.

Parameters

  • signals (dict of :class`~shennong.audio.Audio`) – A dictionnary of input audio signals to process features on, where the keys are item names and values are audio signals.

  • njobs (int, optional) – The number of parallel jobs to run in background. Default to the number of CPU cores available on the machine.

Returns

features (FeaturesCollection) – The computed features on each input signal. The keys of output features are the keys of the input signals.

Raises

ValueError – If the njobs parameter is <= 0

set_params(**params)

Set the parameters of this processor.

Returns

self

Raises

ValueError – If any given parameter in params is invalid for the processor.