FA-91665 / Digital signal filters / Member archive

Forward-backward filter pads with an even mirror · case 05

A ramp input gets a kink at the edges and the filtered ends droop.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input [taps, samples] (integers). Zero-phase filtering: pad = min(3 (len(taps) - 1), len - 1); extend with odd reflection about each end (2 x[0] - x[i] for i = pad..1 before, 2 x[-1] - x[n-1-i] for i = 1..pad after); filter forward with zero initial state, reverse, filter again, reverse, and return the middle len samples.

Why this case matters

Forward-backward filtering is used for offline zero-phase smoothing; padding and reversal slips create edge transients and phase shift.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: random filtfilt 14	`[27, 8]`	`[-53, -12]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.