ZL-167 format sample — 2026-09-08

Original authorized source: ZL-166 PR #26 at b44d716, public/samples/mp4-to-text/product-walkthrough.mp4.
Source SHA256: 581e2434bf687f58e3597c06d797c99e3c63be648ad7f786cb754761cc084f36
Its review-notes.txt records original script/music and local eSpeak NG synthetic narration,
created under the user's demo authorization and available for reuse with the demo.
No customer recording, human recorded voice or voice cloning. This is NOT a phone sample.

M4A creation (AAC stream copied without re-encoding):
ffmpeg -nostdin -v error -i product-walkthrough.mp4 -map 0:a:0 -c:a copy workflow.m4a
Actual local recognition (whisper.cpp 1.9.2; no prompt/script supplied):
ffmpeg -nostdin -v error -i workflow.m4a -ar 16000 -ac 1 /tmp/zl167-workflow.wav
whisper-cli -m /tmp/zl167-ggml-tiny.en.bin -f /tmp/zl167-workflow.wav -l en -ng -t 2 -oj -osrt -otxt -of public/samples/m4a-to-text/recognizer
Model: ggerganov/whisper.cpp ggml-tiny.en.bin, fetched from hf-mirror.com mirror.
See sha256.json for exact model and input/output hashes.
Application export artifacts: pnpm exec tsx scripts/export-m4a-sample.ts
Exports use the existing buildExportFile function and unchanged recognizer text/times.

The recognizer produced two cues and omitted the final masked passage.
It misheard the scripted “Select Export to save the reviewed transcript.”
No manual corrections or human listening sign-off are claimed.
This is local recognition after FFmpeg decoding, NOT a Replicate/application run.
The example ID is an artifact identifier, NOT a persisted application taskId.

Format regression: pnpm test --maxWorkers=2 scripts/check-m4a-formats.test.ts
Tests fully decode the AAC sample, reject its 100-byte truncated derivative,
and reject a derivative with unknown audio sample-entry and descriptor tags.
The unknown-codec fixture is deliberately constructed, not a captured phone failure.
These tests prove local decoder behavior, not cloud codec support or ALAC compatibility.
Real phone M4A, cloud task/export and mobile login acceptance remain pending.