SpectrumExtractor#

Defined in: voxatlas.features.acoustic.spectral.spectrum

class voxatlas.features.acoustic.spectral.spectrum.SpectrumExtractor[source]#

Bases: BaseExtractor

Extract the acoustic.spectral.spectrum feature within the VoxAtlas pipeline.

This public extractor defines the reusable API for computing acoustic.spectral.spectrum from VoxAtlas structured inputs. It consumes None units and produces values aligned to frame units, making the extractor a stable pipeline node that can be cited independently of the surrounding execution machinery.

Algorithm#

The extractor returns the frame-by-frequency magnitude spectrum computed from a short-time Fourier transform.

  1. STFT analysis The waveform is windowed and transformed framewise.

  2. Magnitude projection For frame \(t\) and frequency bin \(k\), the stored value is

    \[S_{t,k} = |X_t(k)|.\]

  3. Matrix packaging The resulting matrix, together with time and frequency axes, is emitted as a MatrixFeatureOutput for downstream spectral descriptors.

Examples

>>> import numpy as np
>>> from voxatlas.audio.audio import Audio
>>> from voxatlas.features.acoustic.spectral.spectrum import SpectrumExtractor
>>> from voxatlas.features.feature_input import FeatureInput
>>> audio = Audio(waveform=np.zeros(1600, dtype=np.float32), sample_rate=16000)
>>> feature_input = FeatureInput(audio=audio, units=None, context={})
>>> params = SpectrumExtractor.default_config.copy()
>>> out = SpectrumExtractor().compute(feature_input, params)
>>> out.unit
'frame'
name: str = 'acoustic.spectral.spectrum'#
input_units: str | None = None#
output_units: str | None = 'frame'#
dependencies: list[str] = []#
default_config: dict = {'frame_length': 0.025, 'frame_step': 0.01, 'window': 'hann'}#
compute(feature_input, params)[source]#

Compute the extractor output for a single pipeline invocation.

This method is the reusable execution entry point for the extractor. It receives the standard FeatureInput bundle, applies the configured algorithm, and returns feature values aligned to the extractor output units for storage in the pipeline feature store.

Parameters:

  • feature_input (object) – Structured extractor input bundling audio, hierarchical units, and execution context for this feature computation.

  • params (object) – Resolved feature configuration for this invocation. Keys are feature-specific and merged from defaults and pipeline settings.

Returns:

Structured output aligned to the frame unit level when applicable.

Return type:

FeatureOutput

Examples

>>> import numpy as np
>>> from voxatlas.audio.audio import Audio
>>> from voxatlas.features.acoustic.spectral.spectrum import SpectrumExtractor
>>> from voxatlas.features.feature_input import FeatureInput
>>> audio = Audio(waveform=np.zeros(1600, dtype=np.float32), sample_rate=16000)
>>> feature_input = FeatureInput(audio=audio, units=None, context={})
>>> params = SpectrumExtractor.default_config.copy()
>>> result = SpectrumExtractor().compute(feature_input, params)
>>> result.values.ndim
2