Allpass

Audio Single output Transform

Apply a two-pole all-pass filter.

FFmpeg filter: allpass — 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 Allpass(…));
$result = $node->outputs()[0];

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

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

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
frequency	float	3000	0–999999	set central frequency
width_type	AllpassWidthType	q	h, q, o, s, k	set filter-width type
width	float	0.707	0–99999	set width
mix	float	1	0–1	set mix
channels	string	all	—	set channels to filter
normalize	bool	false	—	normalize coefficients
order	int	2	1–2	set filter order
transform	AllpassTransformType	di	di, dii, tdi, tdii, latt, svf, zdf	set transform type
precision	AllpassPrecision	auto	auto, s16, s32, f32, f64	set filtering precision

FFmpeg also names these options (use the parameter shown above): f → frequency, t → width_type, w → width, m → mix, c → channels, n → normalize, o → order, a → transform, r → precision.

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