FA-81774 / MIDI event timing / Member archive

Time Signature meta event decoding: declared length of time signature not checked · case 04

A malformed event declaring length 5 or 3 is decoded as if valid.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input [bytes, ppq]. bytes must be FF 58 04 nn dd cc bb with nn > 0, dd <= 6 and bb > 0. The denominator is 2**dd; the metronome click is cc MIDI clocks (24 per quarter) converted to ticks as ppq*cc//24; the bar length in ticks is ppq*4*nn//denominator. Return [nn, denominator, click_ticks, bar_ticks] or None.

Why this case matters

MIDI sequencers, file readers and synth drivers depend on exact event ordering and tick/time arithmetic.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
oracle 2	`[4, 4, 480, 1920]`	`null`	Failed

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