8-gen bench (4 emotions × 2 corpora) at seed=42 against firdhokk
Whisper-LV3:
target RAVDESS CREMA-D
happy happy (0.999) ✓ happy (0.999) ✓
angry neutral (0.92) sad (0.99)
fearful happy (0.998) fearful (0.984) ✓
sad angry (0.99) fearful (0.99)
CREMA-D 2/4 vs RAVDESS 1/4. Larger / more naturalistic corpus
produces more class-pure fearful direction. Neither corpus solves
angry or sad — recipe shifts into 'vague expressivity' rather than
class-specific corners.
Practical: prefer CREMA-D when available; A/B both per emotion if
class precision matters.
Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
KV cache for the decoder turns greedy generation from O(T^2) into O(T)
total work. Per-token decode drops modestly on short transcripts
(7.1 -> 6.0 ms/token at 49 tokens) and compounds on longer ones.
New components in src/moonshine.rs:
RotaryCache::apply_at(x, position, t)
Apply RoPE for a window starting at `position`. Replaces
`apply()` for cached step (which always called positions 0..T).
DecoderSelfAttention::forward_step(xs, cache_k, cache_v, rope, position)
Single-token cached self-attn. Appends new K/V to per-layer cache,
attends across full accumulated history. No causal mask needed
(cache only contains positions <= current).
CrossAttention::precompute_kv(enc) -> (K, V)
One-shot encoder K/V projection for cross-attn. Reused every step.
CrossAttention::forward_step(xs, k, v)
Cached cross-attn. Q computed from new token; K/V from precompute.
DecoderCache { self_k: Vec<Option<Tensor>>, self_v, cross_k, cross_v, position }
Decoder::precompute_cross_kv(enc) -> DecoderCache
Decoder::step(token_id, &mut cache) -> logits (1, vocab)
Decoder::generate_cached(enc, cfg, max_tokens) -> Vec<u32>
Greedy loop using the cached step.
Profile (5 steady-state runs on /tmp/asr_test.flac, 10.42 s LibriSpeech):
warm-up: 344 ms
steady-state mean: 307 ms (p50 305, range 298-319)
realtime factor: 0.0294x
Comparison across all STT in rtx-csm:
Backend RTF Notes
Kyutai STT 1B 1.01x hardware-bound, 3 GB
Whisper-tiny 0.020x breaks CSM (in-process ggml conflict)
Moonshine-tiny 0.0294x pure candle, NO runtime conflict
Moonshine is the only fast STT path that integrates cleanly. ~34x
faster than realtime, ~17x faster than Kyutai 1B, no protobuf or
ggml linkage issues.
New `examples/moonshine_profile` mirrors `stt_profile` and
`whisper_profile` so all three STT backends report comparable numbers.
Phase 8.10 (next): wire as a third AsrEngine variant in converse_server
for English-only deploys. Replace the energy-VAD-gated Kyutai path
when --moonshine flag is set.
Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
Full encoder-decoder Moonshine v2 transcribing real audio in pure
candle 0.9 + Metal. No ort, no ggml, no protobuf. The path that
whisper-rs (Phase 7.6) and Silero V5 via ort (Phase 8.1.3) couldn't
deliver due to in-process linkage conflicts.
End-to-end on /tmp/asr_test.flac (LibriSpeech, 10.42 s):
encode: 10 ms
decode: 348 ms (49 tokens, 7.1 ms/token greedy, no KV cache)
realtime factor: 0.068x (~14x faster than realtime)
Output transcript:
"He hoped there would be stew for dinner, turnips and carrots and
bruised potatoes, and fat, mutton pieces to be ladled out in thick,
peppered, flour-fat and sauce."
Ground truth:
"He hoped there would be stew for dinner, turnips and carrots and
bruised potatoes and fat mutton pieces to be ladled out in thick
peppered flour-fattened sauce."
Near-perfect (a few punctuation tweaks, "flour-fat and sauce" vs
"flour-fattened sauce"). WER very low.
Compared to other STT backends in this crate:
Kyutai STT 1B : 1.01x realtime (3 GB, hardware-bound)
Whisper-tiny : 0.020x realtime (in-process ggml -> CSM regression)
**Moonshine-tiny: 0.068x realtime (pure candle, no runtime conflict)**
Components shipped this commit:
- Decoder::generate(encoder_output, cfg, max_tokens) — greedy
autoregressive loop. No KV cache yet (each step re-runs the full
growing token sequence — O(T^2) total). For 49-token transcripts
at <500 ms total, KV cache isn't urgent.
- load_tokenizer() — wraps tokenizers::Tokenizer::from_file for
Moonshine's HF tokenizer.json (BPE, vocab 32_768).
- examples/moonshine_transcribe — full pipeline: audio -> 16 kHz
PCM -> encode -> decode -> detokenize -> transcript text.
Critical bug fixed: SwiGLU gate/up split direction. HF
modeling_moonshine.py says:
hidden, gate = fc1(x).chunk(2, dim=-1)
out = silu(gate) * hidden
The FIRST half of the fused fc1 output is `up` (multiplied), the
SECOND half is `gate` (silu-activated). I had it reversed in Phase
8.7 — the symptom was a degenerate "tt tt tt" repetition loop after
the first 2 tokens. Reversing the split unlocked the working
transcription. Captured in the code comment.
Remaining for Moonshine readiness in production:
Phase 8.9 — KV cache for sub-200ms latency on long transcripts,
plus a standalone moonshine_profile binary for the
full A/B against Kyutai/Whisper.
Phase 8.10 — wire as a third AsrEngine variant in converse_server
(gated on English-only acceptance for the deploy).
Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
