---
library_name: pytorch
license: apache-2.0
---

# Conformer-CTC Small (Ambarella N1-655 CVflow v3 NVP)

Conformer-CTC Small is a convolution-augmented Transformer speech recognition model trained with Connectionist Temporal Classification (CTC) loss for English automatic speech recognition (ASR).

Original paper: [Conformer: Convolution-augmented Transformer for Speech Recognition](https://arxiv.org/abs/2005.08100)

Model Configuration:
- Reference implementation: [https://github.com/NVIDIA/NeMo](https://github.com/NVIDIA/NeMo)
- Original Weight: [https://huggingface.co/csukuangfj/sherpa-onnx-nemo-ctc-en-conformer-small](https://huggingface.co/csukuangfj/sherpa-onnx-nemo-ctc-en-conformer-small)
- Dataset: NeMo ASRSet (LibriSpeech, Fisher, Switchboard, WSJ, NSC, Mozilla Common Voice)
- License: Apache-2.0 (`LICENSE`)
- Support Cooper version:
  - CNNGen: `[3.9.0 / n1-655x]` (`cavalry_gen 3.0.4`)

## Upstream Attribution & Modification Notice
- **Upstream Copyright**: Copyright (c) NVIDIA CORPORATION & Affiliates (NVIDIA NeMo `stt_en_conformer_ctc_small`) and Copyright (c) Xiaomi Corporation / `sherpa-onnx` contributors (`csukuangfj/sherpa-onnx-nemo-ctc-en-conformer-small`), licensed under the Apache License, Version 2.0.
- **Modification Notice (Apache-2.0 Section 4(b))**: Modified by Ambarella International LLC (2026). Fixed dynamic time dimension to static `[1, 80, 1024]` (10.24 s window), quantized to mixed FP16/INT8 via Ambarella CNNGen (`onnx_surgery` -> `vas` -> `cavalry_gen 3.0.4`), and compiled to CVflow v3 N1-655 (`vdg_arch = 0xB`) Cavalry DAG binary format (`n1-655_conformer_ctc_small_amba_optimized.bin`).

## NVP Port & Runtime Specification
- **Target SoC**: Ambarella N1-655 (`vdg_arch = 0xB`, CVflow v3 `cavalry_gen` 3.0.4)
- **Input port**: `audio_signal` `[1, 80, 1024]` IEEE FP16 (16 kHz PCM -> 80-bin Kaldi log-Mel, 25 ms Povey window, 10 ms hop, per-feature mean/std normalized)
- **Output port**: `logprobs` `[1, 256, 1025]` IEEE FP16 (CTC greedy decode with blank ID `1024` against `tokens.txt`)

| Model | Device | Compression | Model Link |
| :---: | :---: | :---: | :--- |
| Conformer | N1-655 | Amba_optimized | [Model_Link](https://huggingface.co/cchiou-amba/Conformer/blob/main/n1-655_conformer_ctc_small_amba_optimized.bin) |