convert_midi_track_to_keys_wire builds its own inline tempo map and
divides by the raw midi.ticks_per_beat at two sites (the tempo-table
precompute and the tick_to_seconds closure). A malformed header with
division == 0 raised ZeroDivisionError, and an SMPTE division (which
mido returns as a NEGATIVE signed short) produced negative/garbage
note times.
Guard the divisor with `ticks_per_beat if ticks_per_beat > 0 else 480`
so both the zero and negative cases fall back to the SMF default. The
`> 0` form (not `or 480`) is required because a negative value is
truthy and would slip past `or`. Positive-division behavior is
unchanged.
Follow-up to #796, which fixed the same class of bug in the newer
convert_midi_tempo_map / _build_tick_to_seconds path.
Adds two focused tests: division == 0 no longer crashes and emits a
non-negative time, and a negative/SMPTE division yields sane
non-negative times.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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