Trait beat_detector::Strategy

pub trait Strategy {
    fn is_beat(&self, samples: &[i16]) -> Option<BeatInfo>;
    fn kind(&self) -> StrategyKind;
    fn name() -> &'static str
    where
        Self: Sized;
    fn description() -> &'static str
    where
        Self: Sized;
    fn min_duration_between_beats_ms() -> u32
    where
        Self: Sized;

    fn last_beat_beyond_threshold(&self, state: &AnalysisState) -> bool
    where
        Self: Sized,
    { ... }
    fn amplitude_high_enough(&self, w_stats: &WindowStats) -> bool { ... }
}

Common abstraction over a beat detection strategy. Each strategy keeps ongoing audio samples, for example from microphone. Strategies should have an internal mutable state via interior mutability to compare sample windows (and analysis) against previous values.

Required methods

fn is_beat(&self, samples: &[i16]) -> Option<BeatInfo>

Checks if inside the samples window a new beat was recognized. If so, it returns Some with BeatInfo as payload.

Implementations may buffer previous samples and combine them with the latest, i.e. make a sliding window.

fn kind(&self) -> StrategyKind

Convenient getter to get the StrategyKind of a strategy. This is a 1:1 mapping.

fn name() -> &'static str where
    Self: Sized, 

A nice name for the algorithm, displayable in user interfaces.

fn description() -> &'static str where
    Self: Sized, 

A textual description of the algorithm to help the user to select the right one.

fn min_duration_between_beats_ms() -> u32 where
    Self: Sized, 

Duration in ms after each beat. Useful do prevent the same beat to be detected as two beats. This is a constant per strategy, because more advanced strategies can cope with small durations (50ms) whereas “stupid”/basic strategies may need 400ms. This is a function instead of an associated constant, because otherwise the build fails with “Strategy cannot be made into an object”

Provided methods

fn last_beat_beyond_threshold(&self, state: &AnalysisState) -> bool where
    Self: Sized, 

Common implementation for all strategies which checks if the last beat is beyond the threshold. Of not, we can return early and do not need to check if a beat is in the given sample.

fn amplitude_high_enough(&self, w_stats: &WindowStats) -> bool

Common implementation for all strategies which checks if the current windows/frames max amplitude (i16) is above a value where a beat could happen in theory (discard noise/silence/break between songs)

Implementors