Local Whisper transcription (#10)

* First pass at Whisper transcription

* deletions

* Revise based on feedback, add autopep8

src/dailyai/services/whisper_ai_services.py

@@ -0,0 +1,55 @@
+"""This module implements Whisper transcription with a locally-downloaded model."""
+import asyncio
+from enum import Enum
+import logging
+from typing import BinaryIO
+from faster_whisper import WhisperModel
+from dailyai.services.local_stt_service import LocalSTTService
+
+
+class Model(Enum):
+    """Class of basic Whisper model selection options"""
+    TINY = "tiny"
+    BASE = "base"
+    MEDIUM = "medium"
+    LARGE = "large-v3"
+    DISTIL_LARGE_V2 = "Systran/faster-distil-whisper-large-v2"
+    DISTIL_MEDIUM_EN = "Systran/faster-distil-whisper-medium.en"
+
+
+class WhisperSTTService(LocalSTTService):
+    """Class to transcribe audio with a locally-downloaded Whisper model"""
+    _model: WhisperModel
+
+    # Model configuration
+    _model_name: Model
+    _device: str
+    _compute_type: str
+
+    def __init__(self, model_name: Model = Model.DISTIL_MEDIUM_EN,
+                 device: str = "auto",
+                 compute_type: str = "default"):
+
+        super().__init__()
+        self.logger: logging.Logger = logging.getLogger("dailyai")
+        self._model_name = model_name
+        self._device = device
+        self._compute_type = compute_type
+        self._load()
+
+    def _load(self):
+        """Loads the Whisper model. Note that if this is the first time
+        this model is being run, it will take time to download."""
+        model = WhisperModel(
+            self._model_name.value,
+            device=self._device,
+            compute_type=self._compute_type)
+        self._model = model
+
+    async def run_stt(self, audio: BinaryIO = None) -> str:
+        """Transcribes given audio using Whisper"""
+        segments, _ = await asyncio.to_thread(self._model.transcribe, audio)
+        res: str = ""
+        for segment in segments:
+            res += f"{segment.text} "
+        return res