88 lines
5.6 KiB
Markdown
88 lines
5.6 KiB
Markdown
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# DTW diagnostic: strict UTF-8 failure
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Status: internal CPU diagnosis, 2026-10-13. No accepted speech/retrieval score,
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production ASR integration or new media rating follows from this evidence.
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Google EmbeddingGemma 2 remains the production semantic model.
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The original fifteen-window DTW experiment stopped on strict UTF-8 parsing.
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Its temporary raw output was cleaned, so that first run's exact bytes could not
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be inspected. Its partial report remains unchanged. A separate coordinator-
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authorized diagnostic reproduced exactly the second `music01` window: source
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offset 30000 ms, duration 30000 ms, primary audio stream, 480000 decoded samples.
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No labels selected text/timestamps, and the whole experiment was not rerun.
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## Revalidated execution
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The whisper.cpp checkout was clean at pinned commit
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`d1be6fde11ac6e0407606b4e42fe72d34add8037`. Before execution, the fixture and
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source hashes, base model size/hash, worker hash and both decoder hashes were
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checked against frozen evidence. The owned runner retained raw output, WAV,
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probe, stderr and report directly under ignored
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`.searchi/speech/dtw-window-diagnostic-v1`; no temporary cleanup removed them.
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| Artifact | SHA-256 |
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| --- | --- |
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| Frozen fixture | `b4e465a0eb9582b826eebd2a20797e1680e4907e336d02d0ef2194e2ba0af393` |
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| Source music01 | `29fcd20414ee19c2a5aa4339eaf6375079dc87959051ab0aea32c76df52f34dc` |
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| CPU worker | `12c681b4bcd9c7679b647b9a041e121a2f9e72cb2a9c6f189f529ec8b79c36f8` |
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| Multilingual base model | `60ed5bc3dd14eea856493d334349b405782ddcaf0028d4b5df4088345fba2efe` |
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| FFmpeg | `b778ca5786ee4b0b4f37f34478617093d2fdb9a532d281fb76cda69d1d579d46` |
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| FFprobe | `4e1b0afd27bf02d79739f27b2d650137470925afb19d54b5e89a708b7a389236` |
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| Raw JSON, 29148 bytes | `f1de2c295b0c9a223619abe6dbf34823be6a6aa3dbcad69fea1d6121fa0c200e` |
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| Native log | `28d174198a3ef980aa5c8c1237618f450a19b0a80c8a270209dce113a8de3a7a` |
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| Diagnostic report | `b4b0dedfac6365c59793806801b1fc5d9f8f203891b623fb86ad508352ad0114` |
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Windows VM execution forced CPU: `SEARCHI_FORCE_CPU=1`, native flags
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`--no-gpu --threads 1 --processors 1 --language auto --output-json-full
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--dtw base --no-flash-attn`, verified base model and the decoded owned WAV.
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The existing bounded decoder used absolute 30-second seeking and sample trimming;
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its output contained exactly 480000 samples. Native ASR exited zero after
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42493.25 ms; decoding took 271.42 ms. The owned diagnostic runner exited zero
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after recording `strict_parse: rejected`. This is not a successful ASR result
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or a warmed throughput measurement. No other model inference ran concurrently
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under this coordinator's CPU slot; unrelated VM load was not instrumented.
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## Exact failure and pinned native source
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Strict UTF-8 decoding rejects bytes **1137–1138** (zero-based half-open range
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1137–1139). The segment text ends with bytes `E2 80` immediately before the
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closing JSON quote: a three-byte UTF-8 sequence has no final continuation byte.
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The last ordinary token, id 913, also ends with exactly `E2 80` at byte 28900.
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Earlier token text contains complete `E2 80 8D` codepoints. Raw bytes were
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inspected directly, without replacement decoding or writing repaired JSON.
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The pinned native core constructs segment text by concatenating token strings.
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The CLI full-JSON serializer merges adjacent token byte pieces while a codepoint
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needs continuation **and another token exists**. At the last token there is no
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continuation to merge; it writes the remaining incomplete bytes. Its segment
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text serializer likewise writes the already incomplete segment bytes. The
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escaping function only escapes quotes/backslashes; it cannot restore a missing
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codepoint byte. Thus this is incomplete recognized byte output, reproduced in
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both segment and token text, rather than a Python ANSI conversion or DTW time
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unit error. The exact internal reason the decoder terminated this token sequence
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has not been instrumented and remains unproven.
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Relevant pinned source: [CLI serializer and token merging](https://github.com/ggml-org/whisper.cpp/blob/d1be6fde11ac6e0407606b4e42fe72d34add8037/examples/cli/cli.cpp),
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[UTF-8 continuation helper](https://github.com/ggml-org/whisper.cpp/blob/d1be6fde11ac6e0407606b4e42fe72d34add8037/examples/common-whisper.cpp),
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and [segment construction](https://github.com/ggml-org/whisper.cpp/blob/d1be6fde11ac6e0407606b4e42fe72d34add8037/src/whisper.cpp).
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## Minimal next change and limits
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Before changing a native worker, add a strict UTF-8 validator at its JSON boundary
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for original segment strings and merged token strings. If original recognized
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bytes remain invalid after adjacent-token merging, return an explicit typed
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recognition-output error with bounded raw evidence; never replace characters,
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truncate text, synthesize missing bytes or fabricate timestamps. Test a valid
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split codepoint and an incomplete final codepoint. This makes the failure
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machine-readable; it does **not** repair recognition or establish improved
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retrieval. An alternative timestamp/recognition policy must be declared and
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evaluated separately before any default changes.
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The Python harness already fails closed, retains bounded raw bytes with SHA and
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parse positions, and atomically records an incomplete, ineligible checkpoint.
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The original partial DTW report contains three NASA windows with 21 valid
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point-based sentence spans and one separately retained ordinary-interval error.
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It lacks remaining piano windows and three other competitors. Neither that
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partial report nor this one-window diagnosis can receive an accepted quality
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score. Packaging, independent bilingual speech, silence/music hallucination,
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resource peaks and actual production hybrid integration remain open.
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