Loudnorm

Audio Single output Transform

EBU R128 loudness normalization

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

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

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

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
I	float	-24	-70–-5	set integrated loudness target
LRA	float	7	1–50	set loudness range target
TP	float	-2	-9–0	set maximum true peak
measured_I	float	0	-99–0	measured IL of input file
measured_LRA	float	0	0–99	measured LRA of input file
measured_TP	float	99	-99–99	measured true peak of input file
measured_thresh	float	-70	-99–0	measured threshold of input file
offset	float	0	-99–99	set offset gain
linear	bool	true	—	normalize linearly if possible
dual_mono	bool	false	—	treat mono input as dual-mono
print_format	LoudnormPrintFormat	none	none, json, summary	set print format for stats

FFmpeg also names these options (use the parameter shown above): i → I, lra → LRA, tp → TP, measured_i → measured_I, measured_lra → measured_LRA, measured_tp → measured_TP.

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