broadcast-loudness 0.1.0

EBU R 128 / ITU-R BS.1770-5 loudness measurement: K-weighting, integrated/short-term/momentary loudness (LUFS), loudness range (LRA), and true-peak (dBTP). no_std + alloc.
Documentation 
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use thiserror::Error;

/// Loudness measurement error.
#[derive(Debug, Error)]
#[non_exhaustive]
pub enum Error {
    /// A channel index is out of range for the configured layout.
    #[error("channel index {index} out of range (layout has {layout} channels)")]
    ChannelOutOfRange {
        /// The requested channel index.
        index: usize,
        /// The channel count of the configured layout.
        layout: usize,
    },

    /// Push was called after `finish()`.
    #[error("meter has been finished, no more samples accepted")]
    Finished,

    /// Too few samples provided for the channel count.
    #[error("expected {expected} channels, got {got}")]
    ChannelMismatch {
        /// Number of channels expected.
        expected: usize,
        /// Number of channels provided.
        got: usize,
    },

    /// The K-weighting filter coefficients are only specified for 48 kHz
    /// (ITU-R BS.1770-5 Annex 1 Tables 1–2). The spec states that other
    /// sample rates "require different coefficient values" but does not
    /// tabulate them or provide a formula.
    ///
    /// Resample the input to 48 kHz before measurement.
    #[error(
        "K-weighting coefficients are only defined for 48 kHz, got {got} Hz (ITU-R BS.1770-5 Annex 1). Resample to 48 kHz."
    )]
    UnsupportedSampleRate {
        /// The unsupported sample rate requested.
        got: u32,
    },

    /// A non-finite sample (NaN or ±Infinity) was passed to the meter.
    ///
    /// Non-finite values are rejected because they propagate through
    /// the IIR filter state and permanently poison all subsequent
    /// readings. The caller should either skip, replace, or clamp
    /// such samples before feeding them.
    #[error("non-finite sample at index {index} (channel {channel}): {value}")]
    NonFiniteSample {
        /// The index of the non-finite sample in the push call.
        index: usize,
        /// The channel index (zero-based) of the non-finite sample.
        channel: usize,
        /// The non-finite value received.
        value: f64,
    },

    /// A feature is not yet implemented.
    #[error("{what} is not yet implemented")]
    NotImplemented {
        /// Description of the missing feature.
        what: &'static str,
    },
}

/// Result type for loudness operations.
pub type Result<T> = core::result::Result<T, Error>;