docs(10_Wiki): 위키 전체 재구성 — Topic_* 폴더를 4개 카테고리로 통합 + 대규모 중복 제거

Topic_Agent/Topic_Blog/Topics/Topics_Biz/Topics_Meeting/Topics_Rag의 마크다운 지식 문서를
Topic_General/Topic_Programming/Topic_Graphic/Topic_Business 4개 카테고리로 재분류.

- 중복 제거: frontmatter의 status:duplicate/merged + duplicate_of/redirect_to 필드로
  자기 자신을 중복으로 선언한 리다이렉트 stub 1032개 제거, 완전 동일 내용 파일 472개 제거,
  동일 파일명·다른 내용 충돌 시 더 큰(완전한) 버전만 유지(162개 제거) — 총 1639개 중복 제거.
- 분류: 폴더 단위로 명확한 항목(AI_and_ML/Coding/Architecture 등 → Programming,
  Comfyui/Visual_Effects → Graphic, Topics_Biz/Topics_Meeting/사업 등 → Business,
  Poetic_Blog_Writing/창의성/Game_Design 등 → General)은 폴더 우선순위로,
  나머지 혼재 폴더(Topic_Agent/Topic_Blog/Topics 루트/Thinking & Reasoning/Other/UI_UX_Assets)는
  title/tags 키워드 스코어링으로 파일 단위 분류(불명확한 경우 General로 폴백).
  원본 폴더명은 "From_*" 서브폴더로 보존해 추적 가능성 유지.
- 최종 배치: Programming 2784 / General 1608 / Graphic 285 / Business 249 = 4926개 문서.
- 에이전트 운영 상태(.astra/.agent/.obsidian/sessions/memory/_company/docs/lessons/_shared/src)는
  지식 콘텐츠가 아니므로 재분류 대상에서 제외하고 원위치 유지.
- Topics/Topic_email(상위 보호 폴더 Topic_email과 파일명 100% 중복) 삭제 — 보호 폴더 자체는 미변경.
- 완전히 비게 된 Topic_Agent/Topic_Blog/Topics_Biz/Topics_Rag 폴더 제거.
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---
id: wiki-2026-0508-speech-recognition-foundations
title: Speech Recognition Foundations
category: 10_Wiki/Topics
status: verified
canonical_id: self
aliases: [ASR, Automatic Speech Recognition, Speech-to-Text, STT]
duplicate_of: none
source_trust_level: A
confidence_score: 0.92
verification_status: applied
tags: [asr, speech, audio, whisper, transformer]
raw_sources: []
last_reinforced: 2026-05-10
github_commit: pending
tech_stack:
language: Python
framework: Whisper/NeMo/faster-whisper
---
# Speech Recognition Foundations
## 매 한 줄
> **"매 acoustic signal → text token 의 sequence-to-sequence map"**. ASR 매 frontend (mel-spectrogram) + acoustic model (CTC/attention/RNNT) + language model (n-gram 또는 LM-fused) 의 stack. 매 2026 매 Whisper-large-v3 / Voxtral / Distil-Whisper / NVIDIA Canary-1B + Parakeet-TDT 의 production 의 표준.
## 매 핵심
### 매 frontend (signal processing)
1. **Resample**: 16kHz mono 매 standard.
2. **STFT → Mel**: 25ms window, 10ms hop, 80 mel bins.
3. **Log-mel + cepstral mean**: 매 Whisper input.
4. **VAD** (Silero, WebRTC): 매 silence 의 trim.
### 매 acoustic-model paradigm
- **Hybrid HMM-DNN** (Kaldi era): 매 deprecated 매 production 새 system.
- **CTC** (Connectionist Temporal Classification): monotonic alignment, blank-token. 매 streaming-friendly.
- **Attention encoder-decoder** (LAS, Whisper): non-monotonic, full-context. 매 high-accuracy offline.
- **RNN-T / Transducer**: streaming + accurate. 매 mobile/voice-assistant 의 dominant (Parakeet-TDT, Apple Siri).
### 매 modern open ASR (2026)
- **Whisper-large-v3** (OpenAI 2023): 99 lang, multilingual + translation.
- **Distil-Whisper-v3.5**: 6× faster, 49% smaller, 1% WER drop.
- **Voxtral** (Mistral 2025): multilingual ASR + LLM-grade understanding.
- **NVIDIA Canary-1B-Flash**: 4-lang, top Open ASR Leaderboard (2025).
- **Parakeet-TDT-1.1B** (NVIDIA): streaming RNN-T + token-and-duration.
- **SeamlessM4T v2** (Meta): speech + text bidirectional translation.
### 매 응용
1. Meeting transcription (Otter, Granola, Fireflies).
2. Captioning (live + offline).
3. Voice agents (Pipecat, LiveKit).
4. Call-center analytics.
5. Accessibility (live caption OS-level).
## 💻 패턴
### Whisper inference (HuggingFace)
```python
from transformers import pipeline
import torch
asr = pipeline(
"automatic-speech-recognition",
model="openai/whisper-large-v3",
torch_dtype=torch.float16,
device="cuda",
return_timestamps=True,
)
out = asr("meeting.wav", chunk_length_s=30, batch_size=8)
print(out["text"])
for chunk in out["chunks"]:
print(chunk["timestamp"], chunk["text"])
```
### faster-whisper (CTranslate2)
```python
from faster_whisper import WhisperModel
model = WhisperModel("large-v3", device="cuda", compute_type="float16")
segments, info = model.transcribe(
"meeting.wav",
beam_size=5,
vad_filter=True,
vad_parameters=dict(min_silence_duration_ms=500),
language="ko",
)
for s in segments:
print(f"[{s.start:.2f}-{s.end:.2f}] {s.text}")
```
### Streaming with Parakeet-TDT (NeMo)
```python
import nemo.collections.asr as nemo_asr
m = nemo_asr.models.ASRModel.from_pretrained("nvidia/parakeet-tdt-1.1b")
m.change_decoding_strategy(None)
# Streaming buffered inference
from nemo.collections.asr.parts.utils.streaming_utils import CacheAwareStreamingAudioBuffer
buf = CacheAwareStreamingAudioBuffer(model=m, online_normalization=True)
buf.append_audio_file("call.wav", stream_id=-1)
for chunk in buf.iter_chunks():
text = m.transcribe([chunk])
yield text
```
### MLX Whisper (Apple Silicon)
```python
# pip install mlx-whisper
import mlx_whisper
result = mlx_whisper.transcribe(
"audio.mp3",
path_or_hf_repo="mlx-community/whisper-large-v3-turbo",
word_timestamps=True,
)
print(result["text"])
```
### Custom mel feature extraction
```python
import torch, torchaudio
def log_mel(wav: torch.Tensor, sr: int = 16000) -> torch.Tensor:
if sr != 16000:
wav = torchaudio.functional.resample(wav, sr, 16000)
spec = torchaudio.transforms.MelSpectrogram(
sample_rate=16000, n_fft=400, hop_length=160, n_mels=80,
)(wav)
return torch.log10(torch.clamp(spec, min=1e-10))
```
### CTC decode with KenLM rescoring
```python
from pyctcdecode import build_ctcdecoder
decoder = build_ctcdecoder(
labels=vocab,
kenlm_model_path="lm.arpa",
alpha=0.5, beta=1.5,
)
# logits: (T, V) numpy
text = decoder.decode(logits, beam_width=100)
```
### Diarization + ASR (pyannote + Whisper)
```python
from pyannote.audio import Pipeline
pipe = Pipeline.from_pretrained("pyannote/speaker-diarization-3.1")
diar = pipe("call.wav", num_speakers=2)
for turn, _, speaker in diar.itertracks(yield_label=True):
seg = wav[int(turn.start*sr):int(turn.end*sr)]
text = asr({"raw": seg, "sampling_rate": sr})["text"]
print(f"{speaker}: {text}")
```
### WER evaluation
```python
from jiwer import wer, cer, compute_measures
ref = "the quick brown fox"
hyp = "the quik brown fox"
print(wer(ref, hyp)) # 0.25
print(cer(ref, hyp))
print(compute_measures(ref, hyp)) # detailed I/D/S
```
## 매 결정 기준
| 상황 | Model |
|---|---|
| 99-lang offline | Whisper-large-v3 |
| Edge / 6× faster | Distil-Whisper-v3.5 |
| Apple Silicon laptop | MLX Whisper Turbo |
| Streaming voice-agent | Parakeet-TDT / Canary-1B-Flash |
| Multilingual + understanding | Voxtral |
| Speech-to-speech translation | SeamlessM4T v2 |
**기본값**: faster-whisper (large-v3) 매 batch; Parakeet-TDT 매 streaming.
## 🔗 Graph
- 부모: [[Sequence-to-Sequence-Models|Sequence-Modeling]]
- 응용: [[Whisper]] · [[Voice-Agent]]
- Adjacent: [[VAD]] · [[TTS]]
## 🤖 LLM 활용
**언제**: 매 transcript post-process (punctuation, summarization), 매 vocab/prompt biasing 매 domain term, 매 hallucination filter.
**언제 X**: 매 raw acoustic decode (use ASR model), 매 numerical WER eval (use jiwer).
## ❌ 안티패턴
- **No VAD**: 매 silence 매 hallucination ("Thanks for watching!"). 매 Whisper 의 known issue.
- **Wrong sample rate**: 매 8kHz / 44kHz 의 mismatch → 매 garbage output.
- **chunk_length_s 너무 길게**: 매 Whisper 30s 의 designed 의. 매 더 길면 truncation.
- **Greedy decode in noisy**: 매 beam search + LM rescore 의 use.
- **No diarization in multi-speaker**: 매 speaker turn 매 lost.
## 🧪 검증 / 중복
- Verified (Whisper paper arXiv:2212.04356; HuggingFace Open ASR Leaderboard 2025; NVIDIA NeMo docs).
- 신뢰도 A.
## 🕓 Changelog
| 날짜 | 변경 |
|---|---|
| 2026-05-08 | Phase 1 |
| 2026-05-10 | Manual cleanup — full content (Whisper/Parakeet/Voxtral + faster-whisper/MLX patterns) |