Struct Limit

pub struct Limit<I>(/* private fields */)
where
    I: Source;

A source filter that applies audio limiting to prevent peaks from exceeding a threshold.

This filter reduces the amplitude of audio signals that exceed the configured threshold level, helping to prevent clipping and maintain consistent output levels. The limiter automatically adapts to mono, stereo, or multi-channel audio sources by using the appropriate internal implementation.

How It Works

The limiter detects peaks in each audio channel independently but applies gain reduction uniformly across all channels. This preserves stereo imaging while ensuring that loud peaks in any channel are controlled. The limiting uses:

• Soft-knee compression: Gradual gain reduction around the threshold
• Attack/release timing: Configurable response speed to level changes
• Peak detection: Tracks maximum levels across all channels
• Gain smoothing: Prevents audible artifacts from rapid gain changes

Created By

Use Source::limit() with LimitSettings to create a Limit source:

use rodio::source::{SineWave, Source};
use rodio::source::LimitSettings;
use std::time::Duration;

let source = SineWave::new(440.0).amplify(2.0);
let settings = LimitSettings::default()
    .with_threshold(-6.0)  // -6 dBFS threshold
    .with_attack(Duration::from_millis(5))
    .with_release(Duration::from_millis(100));
let limited = source.limit(settings);

Performance

The limiter automatically selects the most efficient implementation based on channel count:

• Mono: Single-channel optimized processing
• Stereo: Two-channel optimized with interleaved processing
• Multi-channel: Generic implementation for 3+ channels

Channel Count Stability

Important: The limiter is optimized for sources with fixed channel counts. Most audio files (music, podcasts, etc.) maintain constant channel counts, making this optimization safe and beneficial.

If the underlying source changes channel count mid-stream (rare), the limiter will continue to function but performance may be degraded. For such cases, recreate the limiter when the channel count changes.

Type Parameters

• I - The input audio source type that implements Source

Implementations

impl<I> Limit<I>

where I: Source,

pub fn inner(&self) -> &I

Returns a reference to the inner audio source.

This allows access to the original source’s properties and methods without consuming the limiter. Useful for inspecting source characteristics like sample rate, channels, or duration.

Useful for inspecting source properties without consuming the filter.

pub fn inner_mut(&mut self) -> &mut I

Returns a mutable reference to the inner audio source.

This allows modification of the original source while keeping the limiter wrapper. Essential for operations like seeking that need to modify the underlying source.

pub fn into_inner(self) -> I

Consumes the limiter and returns the inner audio source.

This dismantles the limiter wrapper to extract the original source, allowing the audio pipeline to continue without limiting overhead. Useful when limiting is no longer needed but the source should continue.

Trait Implementations

impl<I> Clone for Limit<I>

where I: Source + Clone,

fn clone(&self) -> Limit<I>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<I> Debug for Limit<I>

where I: Source + Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<I> Iterator for Limit<I>

where I: Source,

fn next(&mut self) -> Option<Self::Item>

Provides the next limited sample.

fn size_hint(&self) -> (usize, Option<usize>)

Provides size hints from the inner limiter.

type Item = <I as Iterator>::Item

The type of the elements being iterated over.

fn next_chunk<const N: usize>( &mut self, ) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_next_chunk)

Advances the iterator and returns an array containing the next N values.

fn count(self) -> usize

where Self: Sized,

Consumes the iterator, counting the number of iterations and returning it.

fn last(self) -> Option<Self::Item>

where Self: Sized,

Consumes the iterator, returning the last element.

fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>>

🔬This is a nightly-only experimental API. (iter_advance_by)

Advances the iterator by n elements.

fn nth(&mut self, n: usize) -> Option<Self::Item>

Returns the nth element of the iterator.

fn step_by(self, step: usize) -> StepBy<Self>

where Self: Sized,

Creates an iterator starting at the same point, but stepping by the given amount at each iteration.

fn chain<U>(self, other: U) -> Chain<Self, <U as IntoIterator>::IntoIter>

where Self: Sized, U: IntoIterator<Item = Self::Item>,

Takes two iterators and creates a new iterator over both in sequence.

fn zip<U>(self, other: U) -> Zip<Self, <U as IntoIterator>::IntoIter>

where Self: Sized, U: IntoIterator,

‘Zips up’ two iterators into a single iterator of pairs.

fn intersperse(self, separator: Self::Item) -> Intersperse<Self>

where Self: Sized, Self::Item: Clone,

🔬This is a nightly-only experimental API. (iter_intersperse)

Creates a new iterator which places a copy of separator between adjacent items of the original iterator.

fn intersperse_with<G>(self, separator: G) -> IntersperseWith<Self, G>

where Self: Sized, G: FnMut() -> Self::Item,

🔬This is a nightly-only experimental API. (iter_intersperse)

Creates a new iterator which places an item generated by separator between adjacent items of the original iterator.

fn map<B, F>(self, f: F) -> Map<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> B,

Takes a closure and creates an iterator which calls that closure on each element.

fn for_each<F>(self, f: F)

where Self: Sized, F: FnMut(Self::Item),

Calls a closure on each element of an iterator.

fn filter<P>(self, predicate: P) -> Filter<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator which uses a closure to determine if an element should be yielded.

fn filter_map<B, F>(self, f: F) -> FilterMap<Self, F>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both filters and maps.

fn enumerate(self) -> Enumerate<Self>

where Self: Sized,

Creates an iterator which gives the current iteration count as well as the next value.

fn peekable(self) -> Peekable<Self>

where Self: Sized,

Creates an iterator which can use the peek and peek_mut methods to look at the next element of the iterator without consuming it. See their documentation for more information.

fn skip_while<P>(self, predicate: P) -> SkipWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that skips elements based on a predicate.

fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Creates an iterator that yields elements based on a predicate.

fn map_while<B, P>(self, predicate: P) -> MapWhile<Self, P>

where Self: Sized, P: FnMut(Self::Item) -> Option<B>,

Creates an iterator that both yields elements based on a predicate and maps.

fn skip(self, n: usize) -> Skip<Self>

where Self: Sized,

Creates an iterator that skips the first n elements.

fn take(self, n: usize) -> Take<Self>

where Self: Sized,

Creates an iterator that yields the first n elements, or fewer if the underlying iterator ends sooner.

fn scan<St, B, F>(self, initial_state: St, f: F) -> Scan<Self, St, F>

where Self: Sized, F: FnMut(&mut St, Self::Item) -> Option<B>,

An iterator adapter which, like fold, holds internal state, but unlike fold, produces a new iterator.

fn flat_map<U, F>(self, f: F) -> FlatMap<Self, U, F>

where Self: Sized, U: IntoIterator, F: FnMut(Self::Item) -> U,

Creates an iterator that works like map, but flattens nested structure.

fn flatten(self) -> Flatten<Self>

where Self: Sized, Self::Item: IntoIterator,

Creates an iterator that flattens nested structure.

fn map_windows<F, R, const N: usize>(self, f: F) -> MapWindows<Self, F, N>

where Self: Sized, F: FnMut(&[Self::Item; N]) -> R,

🔬This is a nightly-only experimental API. (iter_map_windows)

Calls the given function f for each contiguous window of size N over self and returns an iterator over the outputs of f. Like slice::windows(), the windows during mapping overlap as well.

fn fuse(self) -> Fuse<Self>

where Self: Sized,

Creates an iterator which ends after the first None.

fn inspect<F>(self, f: F) -> Inspect<Self, F>

where Self: Sized, F: FnMut(&Self::Item),

Does something with each element of an iterator, passing the value on.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Iterator.

fn collect<B>(self) -> B

where B: FromIterator<Self::Item>, Self: Sized,

Transforms an iterator into a collection.

fn try_collect<B>( &mut self, ) -> <<Self::Item as Try>::Residual as Residual<B>>::TryType

where Self: Sized, Self::Item: Try, <Self::Item as Try>::Residual: Residual<B>, B: FromIterator<<Self::Item as Try>::Output>,

🔬This is a nightly-only experimental API. (iterator_try_collect)

Fallibly transforms an iterator into a collection, short circuiting if a failure is encountered.

fn collect_into<E>(self, collection: &mut E) -> &mut E

where E: Extend<Self::Item>, Self: Sized,

🔬This is a nightly-only experimental API. (iter_collect_into)

Collects all the items from an iterator into a collection.

fn partition<B, F>(self, f: F) -> (B, B)

where Self: Sized, B: Default + Extend<Self::Item>, F: FnMut(&Self::Item) -> bool,

Consumes an iterator, creating two collections from it.

fn is_partitioned<P>(self, predicate: P) -> bool

where Self: Sized, P: FnMut(Self::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_is_partitioned)

Checks if the elements of this iterator are partitioned according to the given predicate, such that all those that return true precede all those that return false.

fn try_fold<B, F, R>(&mut self, init: B, f: F) -> R

where Self: Sized, F: FnMut(B, Self::Item) -> R, R: Try<Output = B>,

An iterator method that applies a function as long as it returns successfully, producing a single, final value.

fn try_for_each<F, R>(&mut self, f: F) -> R

where Self: Sized, F: FnMut(Self::Item) -> R, R: Try<Output = ()>,

An iterator method that applies a fallible function to each item in the iterator, stopping at the first error and returning that error.

fn fold<B, F>(self, init: B, f: F) -> B

where Self: Sized, F: FnMut(B, Self::Item) -> B,

Folds every element into an accumulator by applying an operation, returning the final result.

fn reduce<F>(self, f: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(Self::Item, Self::Item) -> Self::Item,

Reduces the elements to a single one, by repeatedly applying a reducing operation.

fn try_reduce<R>( &mut self, f: impl FnMut(Self::Item, Self::Item) -> R, ) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType

where Self: Sized, R: Try<Output = Self::Item>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (iterator_try_reduce)

Reduces the elements to a single one by repeatedly applying a reducing operation. If the closure returns a failure, the failure is propagated back to the caller immediately.

fn all<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if every element of the iterator matches a predicate.

fn any<F>(&mut self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> bool,

Tests if any element of the iterator matches a predicate.

fn find<P>(&mut self, predicate: P) -> Option<Self::Item>

where Self: Sized, P: FnMut(&Self::Item) -> bool,

Searches for an element of an iterator that satisfies a predicate.

fn find_map<B, F>(&mut self, f: F) -> Option<B>

where Self: Sized, F: FnMut(Self::Item) -> Option<B>,

Applies function to the elements of iterator and returns the first non-none result.

fn try_find<R>( &mut self, f: impl FnMut(&Self::Item) -> R, ) -> <<R as Try>::Residual as Residual<Option<Self::Item>>>::TryType

where Self: Sized, R: Try<Output = bool>, <R as Try>::Residual: Residual<Option<Self::Item>>,

🔬This is a nightly-only experimental API. (try_find)

Applies function to the elements of iterator and returns the first true result or the first error.

fn position<P>(&mut self, predicate: P) -> Option<usize>

where Self: Sized, P: FnMut(Self::Item) -> bool,

Searches for an element in an iterator, returning its index.

fn max(self) -> Option<Self::Item>

where Self: Sized, Self::Item: Ord,

Returns the maximum element of an iterator.

fn min(self) -> Option<Self::Item>

where Self: Sized, Self::Item: Ord,

Returns the minimum element of an iterator.

fn max_by_key<B, F>(self, f: F) -> Option<Self::Item>

where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the maximum value from the specified function.

fn max_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the maximum value with respect to the specified comparison function.

fn min_by_key<B, F>(self, f: F) -> Option<Self::Item>

where B: Ord, Self: Sized, F: FnMut(&Self::Item) -> B,

Returns the element that gives the minimum value from the specified function.

fn min_by<F>(self, compare: F) -> Option<Self::Item>

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> Ordering,

Returns the element that gives the minimum value with respect to the specified comparison function.

fn unzip<A, B, FromA, FromB>(self) -> (FromA, FromB)

where FromA: Default + Extend<A>, FromB: Default + Extend<B>, Self: Sized + Iterator<Item = (A, B)>,

Converts an iterator of pairs into a pair of containers.

fn copied<'a, T>(self) -> Copied<Self>

where T: Copy + 'a, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which copies all of its elements.

fn cloned<'a, T>(self) -> Cloned<Self>

where T: Clone + 'a, Self: Sized + Iterator<Item = &'a T>,

Creates an iterator which clones all of its elements.

fn cycle(self) -> Cycle<Self>

where Self: Sized + Clone,

Repeats an iterator endlessly.

fn array_chunks<const N: usize>(self) -> ArrayChunks<Self, N>

where Self: Sized,

🔬This is a nightly-only experimental API. (iter_array_chunks)

Returns an iterator over N elements of the iterator at a time.

fn sum<S>(self) -> S

where Self: Sized, S: Sum<Self::Item>,

Sums the elements of an iterator.

fn product<P>(self) -> P

where Self: Sized, P: Product<Self::Item>,

Iterates over the entire iterator, multiplying all the elements

fn cmp<I>(self, other: I) -> Ordering

where I: IntoIterator<Item = Self::Item>, Self::Item: Ord, Self: Sized,

Lexicographically compares the elements of this Iterator with those of another.

fn cmp_by<I, F>(self, other: I, cmp: F) -> Ordering

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Ordering,

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

fn partial_cmp<I>(self, other: I) -> Option<Ordering>

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Lexicographically compares the PartialOrd elements of this Iterator with those of another. The comparison works like short-circuit evaluation, returning a result without comparing the remaining elements. As soon as an order can be determined, the evaluation stops and a result is returned.

fn partial_cmp_by<I, F>(self, other: I, partial_cmp: F) -> Option<Ordering>

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> Option<Ordering>,

🔬This is a nightly-only experimental API. (iter_order_by)

Lexicographically compares the elements of this Iterator with those of another with respect to the specified comparison function.

fn eq<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialEq<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are equal to those of another.

fn eq_by<I, F>(self, other: I, eq: F) -> bool

where Self: Sized, I: IntoIterator, F: FnMut(Self::Item, <I as IntoIterator>::Item) -> bool,

🔬This is a nightly-only experimental API. (iter_order_by)

Determines if the elements of this Iterator are equal to those of another with respect to the specified equality function.

fn ne<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialEq<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are not equal to those of another.

fn lt<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less than those of another.

fn le<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically less or equal to those of another.

fn gt<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than those of another.

fn ge<I>(self, other: I) -> bool

where I: IntoIterator, Self::Item: PartialOrd<<I as IntoIterator>::Item>, Self: Sized,

Determines if the elements of this Iterator are lexicographically greater than or equal to those of another.

fn is_sorted(self) -> bool

where Self: Sized, Self::Item: PartialOrd,

Checks if the elements of this iterator are sorted.

fn is_sorted_by<F>(self, compare: F) -> bool

where Self: Sized, F: FnMut(&Self::Item, &Self::Item) -> bool,

Checks if the elements of this iterator are sorted using the given comparator function.

fn is_sorted_by_key<F, K>(self, f: F) -> bool

where Self: Sized, F: FnMut(Self::Item) -> K, K: PartialOrd,

Checks if the elements of this iterator are sorted using the given key extraction function.

impl<I> Source for Limit<I>

where I: Source,

fn current_span_len(&self) -> Option<usize>

Returns the number of samples before the current span ends. None means “infinite” or “until the sound ends”. Should never return 0 unless there’s no more data.

fn sample_rate(&self) -> SampleRate

Returns the rate at which the source should be played. In number of samples per second.

fn channels(&self) -> ChannelCount

Returns the number of channels. Channels are always interleaved.

fn total_duration(&self) -> Option<Duration>

Returns the total duration of this source, if known.

fn try_seek(&mut self, position: Duration) -> Result<(), SeekError>

Attempts to seek to a given position in the current source.

fn buffered(self) -> Buffered<Self>

where Self: Sized,

Stores the source in a buffer in addition to returning it. This iterator can be cloned.

fn mix<S>(self, other: S) -> Mix<Self, S>

where Self: Sized, S: Source,

Mixes this source with another one.

fn repeat_infinite(self) -> Repeat<Self>

where Self: Sized,

Repeats this source forever.

fn take_duration(self, duration: Duration) -> TakeDuration<Self>

where Self: Sized,

Takes a certain duration of this source and then stops.

fn delay(self, duration: Duration) -> Delay<Self>

where Self: Sized,

Delays the sound by a certain duration.

fn skip_duration(self, duration: Duration) -> SkipDuration<Self>

where Self: Sized,

Immediately skips a certain duration of this source.

fn amplify(self, value: f32) -> Amplify<Self>

where Self: Sized,

Amplifies the sound by the given value.

fn amplify_decibel(self, value: f32) -> Amplify<Self>

where Self: Sized,

Amplifies the sound logarithmically by the given value.

fn amplify_normalized(self, value: f32) -> Amplify<Self>

where Self: Sized,

Normalized amplification in [0.0, 1.0] range. This method better matches the perceived loudness of sounds in human hearing and is recommended to use when you want to change volume in [0.0, 1.0] range. based on article: https://www.dr-lex.be/info-stuff/volumecontrols.html

fn automatic_gain_control( self, target_level: f32, attack_time: f32, release_time: f32, absolute_max_gain: f32, ) -> AutomaticGainControl<Self>

where Self: Sized,

Applies automatic gain control to the sound.

fn take_crossfade_with<S: Source>( self, other: S, duration: Duration, ) -> Crossfade<Self, S>

where Self: Sized, Self::Item: FromSample<S::Item>,

Mixes this sound fading out with another sound fading in for the given duration.

fn fade_in(self, duration: Duration) -> FadeIn<Self>

where Self: Sized,

Fades in the sound.

fn fade_out(self, duration: Duration) -> FadeOut<Self>

where Self: Sized,

Fades out the sound.

fn limit(self, settings: LimitSettings) -> Limit<Self>

where Self: Sized,

Applies limiting to prevent audio peaks from exceeding a threshold.

fn linear_gain_ramp( self, duration: Duration, start_value: f32, end_value: f32, clamp_end: bool, ) -> LinearGainRamp<Self>

where Self: Sized,

Applies a linear gain ramp to the sound.

fn periodic_access<F>( self, period: Duration, access: F, ) -> PeriodicAccess<Self, F>

where Self: Sized, F: FnMut(&mut Self),

Calls the access closure on Self the first time the source is iterated and every time period elapses.

fn speed(self, ratio: f32) -> Speed<Self>

where Self: Sized,

Changes the play speed of the sound. Does not adjust the samples, only the playback speed.

fn reverb( self, duration: Duration, amplitude: f32, ) -> Mix<Self, Delay<Amplify<Self>>>

where Self: Sized + Clone,

Adds a basic reverb effect.

fn pausable(self, initially_paused: bool) -> Pausable<Self>

where Self: Sized,

Makes the sound pausable.

fn stoppable(self) -> Stoppable<Self>

where Self: Sized,

Makes the sound stoppable.

fn skippable(self) -> Skippable<Self>

where Self: Sized,

Adds a method Skippable::skip for skipping this source. Skipping makes Source::next() return None. Which in turn makes the Sink skip to the next source.

fn track_position(self) -> TrackPosition<Self>

where Self: Sized,

Start tracking the elapsed duration since the start of the underlying source.

fn low_pass(self, freq: u32) -> BltFilter<Self>

where Self: Sized + Source<Item = f32>,

Applies a low-pass filter to the source. Warning: Probably buggy.

fn high_pass(self, freq: u32) -> BltFilter<Self>

where Self: Sized + Source<Item = f32>,

Applies a high-pass filter to the source.

fn low_pass_with_q(self, freq: u32, q: f32) -> BltFilter<Self>

where Self: Sized + Source<Item = f32>,

Applies a low-pass filter to the source while allowing the q (bandwidth) to be changed.

fn high_pass_with_q(self, freq: u32, q: f32) -> BltFilter<Self>

where Self: Sized + Source<Item = f32>,

Applies a high-pass filter to the source while allowing the q (bandwidth) to be changed.

fn distortion(self, gain: f32, threshold: f32) -> Distortion<Self>

where Self: Sized,

Applies a distortion effect to the sound.