FA-81509 / MIDI event timing / Member archive

SMPTE time-division ticks to microseconds: code 29 timed at 29 frames per second · case 04

Files using 29.97 fps timing run about 3.4% slow because each frame is taken as 1/29 second.

Member previewVariant 4 · 3 implementations · 8 checks per implementation

Case contract

Input [division_high_byte, ticks_per_frame, ticks]. The high byte is a negative frame-rate code in two's complement: 24, 25, 29 (meaning 30000/1001 frames per second) or 30. Microseconds = ticks * 1000000 / (rate * ticks_per_frame), floored once. Invalid codes, non-positive ticks per frame or negative ticks return 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 0	`34482`	`33366`	Failed

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