Module metrics 

Audio signal comparison metrics.

This module provides functions for comparing audio signals and measuring various quality metrics commonly used in audio circuit validation.

Available Metrics

Metric	Function	Description
Normalized RMS Error	normalized_rms_error_db	Overall signal difference (lower is better)
Peak Error	peak_error_db	Maximum sample-level difference
THD	thd_db	Total Harmonic Distortion
THD Error	thd_error_db	THD difference between two signals
Even/Odd Ratio	even_odd_ratio_db	Even vs odd harmonic balance
Spectral Error	spectral_error_db	Frequency domain difference
DC Drift	dc_drift_mv	Low-frequency offset measurement

Example

use pedalkernel_validate::metrics;

let wdf_output: Vec<f64> = vec![0.1, 0.2, 0.3, 0.2, 0.1];
let reference: Vec<f64> = vec![0.1, 0.2, 0.3, 0.2, 0.1];
let sample_rate = 48000.0;

// Compare individual metrics
let rms_err = metrics::normalized_rms_error_db(&wdf_output, &reference);
let peak_err = metrics::peak_error_db(&wdf_output, &reference);

// Or use the combined comparison function
let result = metrics::compare(&wdf_output, &reference, sample_rate, Some(1000.0));
println!("RMS error: {:.1} dB", result.normalized_rms_error_db);
println!("Peak error: {:.1} dB", result.peak_error_db);

Interpreting Results

• RMS Error: -60 dB means error is 0.1% of signal. -80 dB is excellent.
• Peak Error: Maximum instantaneous difference. Usually higher than RMS.
• THD: Pure sine should be < -80 dB. Audible distortion starts around -40 dB.
• Even/Odd Ratio: Push-pull amps should have < -40 dB (even harmonics suppressed)

Modules

ac_accuracy

op_point

Structs

ComparisonResult

Result of comparing WDF output to reference.

Functions

ac_amplitude_drift_db

AC-amplitude drift across a signal: dB difference between the single-bin amplitude of the SECOND half vs the FIRST half of signal.

ac_gain_db

Steady-state, level-independent AC gain ratio in dB at freq_hz: 20*log10(amp_wdf / amp_ref). Positive = WDF louder than the reference.

compare

Compare WDF output to reference with all metrics.

dc_drift_mv

Measure DC drift over time.

dc_offset

Mean (DC offset) of a signal. Use as the AC-coupling / settle guard: an AC-coupled output that has reached steady state has |mean| ≈ 0.

even_odd_ratio_db

Compute even/odd harmonic ratio in dB.

even_odd_ratio_error_db

Compute even/odd harmonic ratio error between WDF and reference in dB.

harmonic_mag_error_db

Compute the maximum harmonic magnitude error between WDF and reference in dB.

normalized_rms_error_db

Compute normalized RMS error in dB.

peak_error_db

Compute peak absolute error in dB relative to reference peak.

single_bin_amplitude

Single-bin DFT amplitude (peak, in signal units) of the component at exactly freq_hz.

spectral_error_db

Compute maximum spectral magnitude error in dB.

thd_db

Compute THD (Total Harmonic Distortion) in dB.

thd_error_db

Compute THD error between WDF and reference in dB.

thd_plus_n_db

Compute THD+N (Total Harmonic Distortion plus Noise) in dB.

thd_plus_n_error_db

Compute THD+N error between WDF and reference in dB.