Biquad

Audio Single output Transform

Apply a biquad IIR filter with the given coefficients.

FFmpeg filter: biquad — the official reference.

Add it to a graph. The explicit form works for every filter — bind it to its input and read the result from outputs():

$node   = $audio->addFilter(new Biquad(…));
$result = $node->outputs()[0];

Shorthand. Single-output filters can skip the node — apply() returns the result stream directly:

$result = $audio->apply(new Biquad(…));

When to use it

TODO — when this filter shines: what it’s the right tool for, what to reach for instead when it isn’t, and how it composes with neighbouring filters.

How to use it

TODO — prose: how the filter actually works and what its key parameters mean (the explanation FFmpeg’s terse option help omits).

Examples

TODO — runnable PHP, with the equivalent ffmpeg CLI alongside.

Gotchas

TODO

See also

TODO

Parameters

Parameter	Type	Default	Range / values	Description
a0	float	1	—
a1	float	0	—
a2	float	0	—
b0	float	0	—
b1	float	0	—
b2	float	0	—
mix	float	1	0–1	set mix
channels	string	all	—	set channels to filter
normalize	bool	false	—	normalize coefficients
transform	BiquadTransformType	di	di, dii, tdi, tdii, latt, svf, zdf	set transform type
precision	BiquadPrecision	auto	auto, s16, s32, f32, f64	set filtering precision
blocksize	int	0	0–32768	set the block size

FFmpeg also names these options (use the parameter shown above): m → mix, c → channels, n → normalize, a → transform, r → precision, b → blocksize.

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Maps to FFmpeg’s biquad filter. Verified against ffmpeg n7.1.1.