46 lines
2.6 KiB
Markdown
46 lines
2.6 KiB
Markdown
# Spectrogram to Audio
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Reconstructs an audio signal from a spectrogram image.
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Source library: `torchaudio`, `torch`
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## Overview
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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.
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## Parameters
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- **image**: The input spectrogram image (`IMAGE` type). Must be provided as a forced input.
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- **window_size**: (FLOAT) The analysis frame size in milliseconds. Must match the value used when creating the spectrogram. Default: 25.0.
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- **hop_size**: (FLOAT) The frame overlap in milliseconds. Must match the original. Default: 15.0.
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- **windowing_func**: The windowing function used. Must match the original. Default: **Hanning**.
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- **autogain**: (BOOLEAN) When `True`, normalizes the audio to prevent clipping. Default: `True`.
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- **max_amp**: (FLOAT) Maximum amplitude scaling factor. Default: 1.0.
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- **max_iter**: (INT) The number of Griffin-Lim iterations. More iterations improve phase accuracy but take longer. Default: 32.
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- **top_db**: (FLOAT) The minimum dB threshold for magnitude values. Default: 80.0.
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- **sampling_rate**: (INT) The sample rate of the output audio in Hz. Default: 22050.
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- **gl_momentum**: (FLOAT) The Griffin-Lim momentum parameter. Default: 0.99.
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- **scaling_method**: The scaling method used when creating the spectrogram. Must match the original.
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- **Linear**, **Quadratic**, **Logarithmic**, **Logarithmic Mel**.
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- **mel_scale**: (BOOLEAN) The Mel scale method used. Must match the original: `htk` (off) or `slaney` (on).
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- **channel**: How to extract the audio channel from the image.
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- **colormap**: Uses the colormap-based intensity.
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- **luminance**: Uses ITU-R BT.601 perceptual luminance weights.
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- **channel_red**: Uses the red channel.
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- **channel_green**: Uses the green channel.
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- **channel_blue**: Uses the blue channel.
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### Optional Parameters
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- **colormap_low**: (STRING) Hex color for low intensity. Default: `#000000`.
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- **colormap_mid**: (STRING) Hex color for mid intensity. Default: `#B73779`.
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- **colormap_high**: (STRING) Hex color for high intensity. Default: `#FCFDBF`.
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## Outputs
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- **audio**: The reconstructed audio as an `AUDIO` object, containing a waveform and sample rate.
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## Additional Considerations
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- Reconstruction quality depends on the number of Griffin-Lim iterations and how closely the parameters match the original encoding.
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