Retried the format probe with the fmt chunk built to synth_xma1_fmt's exact
byte layout, and with the bank's own RIFF sub-wave decoded through the same
pipe as a CONTROL so a broken harness cannot masquerade as a result.
The channel count is the whole story:
bank lead B channels=2 channels=1
VOICE_D_450 16384 1792 46756
VOICE_D_451 2048 1792 896 (all-zero region: control)
VOICE_D_452 14336 1792 30154
VOICE_D_453 45056 1792 203648
VOICE_D_454 59392 1792 294440
channels=2 yields EXACTLY 1792 bytes for every bank regardless of size -- one
frame, then it stops. That constant is the tell. At channels=1 the same data
yields up to 113x more, and the control sub-wave decodes to 13568, so the
pipe works.
Why the previous probe got 0 bytes everywhere is now named: I read
synth_xma1_fmt(2, 2, 48000)'s second argument as a STREAM COUNT when it is a
CHANNEL MASK, and built the WAVEFORMATEX around that misreading.
Also recorded as a refutation, because it was tempting: solving for the
sample rate as decoded-samples / last-subtitle-cue does NOT converge. D_453
implies 21665 Hz -- close enough to 22050 that I nearly wrote it down -- but
D_450 implies 5844 Hz. No single rate explains both, and the decodes are
visibly partial (samples per input byte ranges 2.10-4.96 where a clean decode
would be near-constant).
So the container is identified and the duration is not. Next step recorded:
find why FFmpeg stops early, likely the hardcoded packet/subframe fields.
Artifact: examples/slb_fmt_probe.rs.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMRJjbxLqZtsb5Vb7KunPE
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