The last open question was whether the leading XMA1-mono region duplicates the
RIFF sub-wave, which would make the earlier totals double-count. It does not.
Decoding both parts of every bank to mono PCM and measuring energy:
bank leading secs / RMS riff secs / RMS
VOICE_D_450 0.49 / 158 2.82 / 9898
VOICE_D_451 0.01 / 0 1.58 / 9128
VOICE_D_452 0.31 / 301 2.18 / 9061
VOICE_D_453 2.12 / 9770 0.14 / 14462
VOICE_D_454 3.07 / 10428 0.43 / 11639
Two shapes, and no bank holds the same content twice. In 450/451/452 the
leading region is silence or near-silence (RMS 0-301 against ~9000 for
speech) and the RIFF holds the line. In 453/454 the leading region holds the
line and the RIFF is a short loud tail fragment. Sequential segments of one
clip, so the totals stand and with them the 48 kHz fit.
This also closes the mystery that started the whole thread. The corpus
recorded 450 = 2.8 s, 451 = 1.6 s, 452 = 2.2 s as plausible but 453 = 0.14 s
and 454 = 0.43 s as "far too short". The decoder skips everything before the
first RIFF: for the first three that discards only silence, so they looked
fine; for the last two it discards the line itself and leaves the trailing
fragment. One rule, two outcomes, depending on which segment holds the
speech.
The fix is now well-posed in a way the withdrawn attempt was not: emit the
leading region only when it carries signal. That also avoids the 1524-bank
blast radius that sank the earlier version.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE
4d1be2f175