Audio filters

Audio filters transform an AudioStream. The common ones read as methods; the whole FFmpeg catalog is reachable as Filter classes through apply().

$audio = Media::open('podcast.wav')->audioStream();

$audio->normalizeLoudness(i: -16, tp: -1.5, lra: 11);          // friendly method
$audio->apply(new \FFmpeg\Filter\Loudnorm(i: -16, tp: -1.5));  // the same — any audio filter

Parameters can be a number, an FFmpeg expression, or a per-frame closure — see the Architecture.

A few you’ll reach for

Method	FFmpeg	Does
`normalizeLoudness()`	`loudnorm`	EBU R128 loudness normalization
`duckUnder()`	`sidechaincompress`	Duck one track under another
`mixWith()`	`amix`	Mix tracks together
`limit()`	`alimiter`	Hard-limit peaks
`volume()`	`volume`	Change gain
`fade()`	`afade`	Fade in / out

Full recipes — loudness, ducking, limiting — are in the Examples. A page per filter (parameters, examples, gotchas) follows.

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