Comfy-Org/ComfyUI · error · ValueError

Minimum cutoff must be larger than zero.

Error message

Minimum cutoff must be larger than zero.

What it means

MMAudio VAE copy of the alias-free LowPassFilter1d: raises when cutoff < 0. Cutoff is normalized (0..0.5 relative to Nyquist) for the Kaiser sinc filter, so negative values are rejected at module construction. Config-driven: the value normally comes from the VAE's JSON config.

Source

Thrown at comfy/ldm/mmaudio/vae/alias_free_torch.py:70

        filter_ /= filter_.sum()
        filter = filter_.view(1, 1, kernel_size)

    return filter


class LowPassFilter1d(nn.Module):
    def __init__(self,
                 cutoff=0.5,
                 half_width=0.6,
                 stride: int = 1,
                 padding: bool = True,
                 padding_mode: str = 'replicate',
                 kernel_size: int = 12):
        # kernel_size should be even number for stylegan3 setup,
        # in this implementation, odd number is also possible.
        super().__init__()
        if cutoff < -0.:
            raise ValueError("Minimum cutoff must be larger than zero.")
        if cutoff > 0.5:
            raise ValueError("A cutoff above 0.5 does not make sense.")
        self.kernel_size = kernel_size
        self.even = (kernel_size % 2 == 0)
        self.pad_left = kernel_size // 2 - int(self.even)
        self.pad_right = kernel_size // 2
        self.stride = stride
        self.padding = padding
        self.padding_mode = padding_mode
        filter = kaiser_sinc_filter1d(cutoff, half_width, kernel_size)
        self.register_buffer("filter", filter)

    #input [B, C, T]
    def forward(self, x):
        _, C, _ = x.shape

        if self.padding:
            x = F.pad(x, (self.pad_left, self.pad_right),

View on GitHub (pinned to 1c6d8d45b3)

Solutions

1. Set cutoff in [0, 0.5] (default 0.5)
2. Inspect the VAE config JSON used to build the alias-free modules
3. Restore the original config shipped with the MMAudio checkpoint

Example fix

# before
LowPassFilter1d(cutoff=-0.1)
# after
LowPassFilter1d(cutoff=0.1)

for stage in cfg.get('stages', []):
    c = stage.get('cutoff', 0.5)
    assert 0.0 <= c <= 0.5, f'bad cutoff {c} in stage {stage}'

def is_valid_cutoff(c: float) -> bool:
    return isinstance(c, (int, float)) and 0.0 <= c <= 0.5

When it happens

Trigger: Constructing the MMAudio VAE with a config where any alias-free stage has a negative cutoff, or instantiating LowPassFilter1d directly with cutoff < 0.

Common situations: Editing mmaudio VAE config to tune anti-aliasing; porting configs between BigVGAN-family repos with different cutoff conventions; sentinel defaults (-1) leaking into config.

Related errors

• A cutoff above 0.5 does not make sense.
• Minimum cutoff must be larger than zero.
• A cutoff above 0.5 does not make sense.
• activation incorrectly specified. check the config file and
• Unknown model: {name}

AI-assisted analysis of Comfy-Org/ComfyUI@1c6d8d45b3 (2026-08-14). Data as JSON: /api/errors/81372275c32354ae. Report an issue: GitHub.