Add realtime loopback STT prototype

python/loopback_stt_worker.py

@@ -0,0 +1,133 @@
+import base64
+import json
+import os
+import sys
+import traceback
+from typing import Any
+
+import numpy as np
+from faster_whisper import WhisperModel
+
+
+def resolve_model() -> WhisperModel:
+    model_name = os.environ.get("WHISPER_MODEL", "large-v3-turbo")
+    requested_device = os.environ.get("WHISPER_DEVICE", "auto")
+    requested_compute = os.environ.get("WHISPER_COMPUTE_TYPE", "auto")
+
+    attempts: list[tuple[str, str]] = []
+    if requested_device == "auto":
+        if requested_compute == "auto":
+            attempts.extend(
+                [
+                    ("cuda", "float16"),
+                    ("cuda", "int8_float16"),
+                    ("cpu", "int8"),
+                    ("cpu", "float32"),
+                ]
+            )
+        else:
+            attempts.extend(
+                [
+                    ("cuda", requested_compute),
+                    ("cpu", requested_compute),
+                ]
+            )
+    else:
+        if requested_compute == "auto":
+            compute = "float16" if requested_device == "cuda" else "int8"
+        else:
+            compute = requested_compute
+        attempts.append((requested_device, compute))
+
+    last_error: Exception | None = None
+    for device, compute_type in attempts:
+        try:
+            model = WhisperModel(model_name, device=device, compute_type=compute_type)
+            setattr(model, "_resolved_device", device)
+            setattr(model, "_resolved_compute_type", compute_type)
+            return model
+        except Exception as error:  # noqa: BLE001
+            last_error = error
+
+    assert last_error is not None
+    raise last_error
+
+
+MODEL = resolve_model()
+LANGUAGE = os.environ.get("WHISPER_LANGUAGE", "ko")
+BEAM_SIZE = int(os.environ.get("WHISPER_BEAM_SIZE", "1"))
+
+
+def write(payload: dict[str, Any]) -> None:
+    sys.stdout.write(json.dumps(payload, ensure_ascii=False) + "\n")
+    sys.stdout.flush()
+
+
+def transcribe_pcm16_base64(pcm16_base64: str) -> str:
+    audio_bytes = base64.b64decode(pcm16_base64)
+    audio = np.frombuffer(audio_bytes, dtype=np.int16).astype(np.float32) / 32768.0
+
+    segments, _info = MODEL.transcribe(
+        audio,
+        language=LANGUAGE,
+        task="transcribe",
+        beam_size=BEAM_SIZE,
+        condition_on_previous_text=False,
+        vad_filter=False,
+        without_timestamps=True,
+        word_timestamps=False,
+        temperature=0.0,
+    )
+
+    text_parts: list[str] = []
+    for segment in segments:
+        if segment.text:
+            text_parts.append(segment.text.strip())
+    return " ".join(part for part in text_parts if part).strip()
+
+
+for raw_line in sys.stdin:
+    line = raw_line.strip()
+    if not line:
+        continue
+
+    request = json.loads(line)
+    request_id = request["id"]
+    method = request["method"]
+    params = request.get("params", {})
+
+    try:
+        if method == "ping":
+            write(
+                {
+                    "id": request_id,
+                    "result": {
+                        "model": os.environ.get("WHISPER_MODEL", "large-v3-turbo"),
+                        "device": getattr(MODEL, "_resolved_device", "unknown"),
+                        "compute_type": getattr(MODEL, "_resolved_compute_type", "unknown"),
+                    },
+                }
+            )
+            continue
+
+        if method == "transcribe":
+            text = transcribe_pcm16_base64(params["pcm16_base64"])
+            write(
+                {
+                    "id": request_id,
+                    "result": {
+                        "text": text,
+                    },
+                }
+            )
+            continue
+
+        raise RuntimeError(f"unknown method: {method}")
+    except Exception as error:  # noqa: BLE001
+        traceback.print_exc(file=sys.stderr)
+        write(
+            {
+                "id": request_id,
+                "error": f"{type(error).__name__}: {error}",
+            }
+        )

python/requirements.txt

@@ -0,0 +1 @@
+faster-whisper==1.2.1