Implements AF-Vocoder GAFilter (Interspeech 2025): learnable per-channel
depthwise FIR filter inserted after each Snake/Activation1d in BigVGAN
residual blocks. Initialized as identity so training starts from pretrained
behaviour.
- inject_gafilters() walks resblocks.*.activations and wraps each Activation1d
with _ActivationWithGAFilter — weights appear in vocoder.state_dict() automatically
- Trained alongside Snake alphas in snake_alpha_only mode
- Checkpoint saves has_gafilter + gafilter_kernel_size metadata
- Loader detects metadata and injects before load_state_dict so weights populate correctly
- Controlled by use_gafilter (default True) and gafilter_kernel_size (default 9)
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
EthanfelandClaude Sonnet 4.6
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