sensevoice

SenseVoiceSmall on llama.cpp / GGUF

Run SenseVoiceSmall on the llama.cpp / ggml stack — CPU, edge, a single binary, no Python at runtime. Like whisper.cpp, but for SenseVoice.

Why this exists

SenseVoiceSmall normally runs on PyTorch / ONNX / libtorch. This runtime ports it to ggml + GGUF so it can run CPU-only, offline, embedded in a C/C++ app, with quantized weights. Use it on laptops / phones / edge boxes where there is no GPU and no Python. (For high-QPS GPU serving, the PyTorch/vLLM path is still the way.)

Architecture

SenseVoiceSmall = SAN-M encoder (70 layers) + CTC head — no LLM, no autoregression. The whole pipeline runs in C++:

 audio.wav (16k mono)
      │  kaldi 80-mel fbank + LFR                         (C++)
      ▼
   features [T, 560]
      │  prepend 4 query tokens [lang, event, emotion, itn]
      ▼
   [4 + T, 560]
      │  SAN-M encoder                                    (ggml)  ── sensevoice-small.gguf
      ▼
   encoder out [4+T, 512]
      │  CTC head (Linear 512→25055) → greedy CTC (argmax, dedup, drop blank)
      ▼
   token ids
      │  SentencePiece detok                             (detok.py)
      ▼
   <|zh|><|NEUTRAL|><|Speech|><|woitn|> transcription...

The SAN-M encoder is the same architecture as Fun-ASR-Nano's, so the ggml forward is shared between the two runtimes.

Quickstart

1. Build:

git clone https://github.com/ggml-org/llama.cpp && cd llama.cpp
cp -r /path/to/runtime/llama.cpp/funasr-sensevoice examples/
echo 'add_subdirectory(funasr-sensevoice)' >> examples/CMakeLists.txt
cmake -B build -DGGML_NATIVE=ON -DLLAMA_CURL=OFF
cmake --build build -j --target llama-funasr-sensevoice

2. Convert weights (needs the checkpoint, e.g. FunAudioLLM/SenseVoiceSmall):

python runtime/llama.cpp/export_sensevoice_gguf.py \
    --model_pt <model>/model.pt --mvn <model>/am.mvn \
    --out sensevoice-small.gguf                          # f32, ~936 MB
python runtime/llama.cpp/export_sensevoice_gguf.py --wtype f16 \
    --model_pt <model>/model.pt --mvn <model>/am.mvn \
    --out sensevoice-small-f16.gguf                       # half size

3. Transcribe:

build/bin/llama-funasr-sensevoice -m sensevoice-small.gguf -a audio.wav   # prints transcription text
# --keep-tags keeps the <|lang|>/<|emotion|>/<|event|> tags; --ids prints raw CTC ids

Expected output:

我想问我在滨海新区有房我一直没有照顾孩子...你觉得这是正常的想法吗

The leading <|...|> tags are the predicted language / emotion / event / ITN.

Accuracy & validation

• CTC token ids (C++) vs PyTorch: identical (108/108 on a benchmark clip).
• Detokenized text: matches the FunASR AutoModel output exactly.
• Encoder validated against PyTorch (shared with Fun-ASR-Nano runtime): cosine 1.0.
• Encode time ≈ 1.3 s on CPU for a 44 s clip.

Tips & gotchas

• No CMVN at inference. SenseVoice inference() feeds the raw log-mel fbank to the encoder; it does not apply am.mvn. Applying CMVN makes the model predict <|nospeech|>. (The export script reads am.mvn for completeness but the runtime does not use it.)
• Query tokens (4) are prepended from embed.weight, default indices [language=auto(0), event=1, emotion=2, textnorm=woitn(15)]. Change them for a fixed language or to enable ITN (withitn=14).
• WAV input assumes 16 kHz mono PCM16.
• LayerNorm eps = 1e-5; FSMN = exact f32 shift-accumulate; fbank matches torchaudio.

Files

funasr-sensevoice/        ggml runtime: WAV → CTC token ids
export_sensevoice_gguf.py export encoder + CTC head + query embeddings to GGUF
detok.py                  SentencePiece id → text (bpe model ships with the checkpoint)

Roadmap

• Built-in SentencePiece detok (drop the Python step); arbitrary WAV formats; encoder Q8 quantization; timestamps.