AzelusLightvale-ComfyUI-ARG-Toolkit/web/docs/SpectrogramDecoder.md

Spectrogram to Audio

Reconstructs an audio signal from a spectrogram image.

Source library: torchaudio, torch

Overview

This node is the inverse of the Audio to Spectrogram node. It takes a spectrogram image (or any arbitrary image if you know what you're doing) and reconstructs the original audio waveform using the Griffin-Lim phase reconstruction algorithm. The Griffin-Lim algorithm iteratively estimates the phase information that was lost when the spectrogram was created, allowing reasonable audio reconstruction from magnitude-only data.

Parameters

• image: The input spectrogram image (IMAGE type). Must be provided as a forced input.
• window_size: (FLOAT) The analysis frame size in milliseconds. Must match the value used when creating the spectrogram. Default: 25.0.
• hop_size: (FLOAT) The frame overlap in milliseconds. Must match the original. Default: 15.0.
• windowing_func: The windowing function used. Must match the original. Default: Hanning.
• autogain: (BOOLEAN) When True, normalizes the audio to prevent clipping. Default: True.
• max_amp: (FLOAT) Maximum amplitude scaling factor. Default: 1.0.
• max_iter: (INT) The number of Griffin-Lim iterations. More iterations improve phase accuracy but take longer. Default: 32.
• top_db: (FLOAT) The minimum dB threshold for magnitude values. Default: 80.0.
• sampling_rate: (INT) The sample rate of the output audio in Hz. Default: 22050.
• gl_momentum: (FLOAT) The Griffin-Lim momentum parameter. Default: 0.99.
• scaling_method: The scaling method used when creating the spectrogram. Must match the original.
  • Linear, Quadratic, Logarithmic, Logarithmic Mel.
• mel_scale: (BOOLEAN) The Mel scale method used. Must match the original: htk (off) or slaney (on).
• channel: How to extract the audio channel from the image.
  • colormap: Uses the colormap-based intensity.
  • luminance: Uses ITU-R BT.601 perceptual luminance weights.
  • channel_red: Uses the red channel.
  • channel_green: Uses the green channel.
  • channel_blue: Uses the blue channel.

Optional Parameters

• colormap_low: (STRING) Hex color for low intensity. Default: #000000.
• colormap_mid: (STRING) Hex color for mid intensity. Default: #B73779.
• colormap_high: (STRING) Hex color for high intensity. Default: #FCFDBF.

Outputs

• audio: The reconstructed audio as an AUDIO object, containing a waveform and sample rate.

Additional Considerations

• Reconstruction quality depends on the number of Griffin-Lim iterations and how closely the parameters match the original encoding.