faster_whisper_server/main.py

from __future__ import annotations

import asyncio
import time
from contextlib import asynccontextmanager
from io import BytesIO
from typing import Annotated, Literal, OrderedDict

from fastapi import (
    FastAPI,
    Form,
    Query,
    Response,
    UploadFile,
    WebSocket,
    WebSocketDisconnect,
)
from fastapi.responses import StreamingResponse
from fastapi.websockets import WebSocketState
from faster_whisper import WhisperModel
from faster_whisper.vad import VadOptions, get_speech_timestamps

from faster_whisper_server import utils
from faster_whisper_server.asr import FasterWhisperASR
from faster_whisper_server.audio import AudioStream, audio_samples_from_file
from faster_whisper_server.config import (
    SAMPLES_PER_SECOND,
    Language,
    Model,
    ResponseFormat,
    config,
)
from faster_whisper_server.logger import logger
from faster_whisper_server.server_models import (
    TranscriptionJsonResponse,
    TranscriptionVerboseJsonResponse,
)
from faster_whisper_server.transcriber import audio_transcriber

models: OrderedDict[Model, WhisperModel] = OrderedDict()


def load_model(model_name: Model) -> WhisperModel:
    if model_name in models:
        logger.debug(f"{model_name} model already loaded")
        return models[model_name]
    if len(models) >= config.max_models:
        oldest_model_name = next(iter(models))
        logger.info(
            f"Max models ({config.max_models}) reached. Unloading the oldest model: {oldest_model_name}"
        )
        del models[oldest_model_name]
    logger.debug(f"Loading {model_name}")
    start = time.perf_counter()
    whisper = WhisperModel(
        model_name,
        device=config.whisper.inference_device,
        compute_type=config.whisper.compute_type,
    )
    logger.info(
        f"Loaded {model_name} loaded in {time.perf_counter() - start:.2f} seconds"
    )
    models[model_name] = whisper
    return whisper


@asynccontextmanager
async def lifespan(_: FastAPI):
    load_model(config.whisper.model)
    yield
    for model in models.keys():
        logger.info(f"Unloading {model}")
        del models[model]


app = FastAPI(lifespan=lifespan)


@app.get("/health")
def health() -> Response:
    return Response(status_code=200, content="OK")


@app.post("/v1/audio/translations")
def translate_file(
    file: Annotated[UploadFile, Form()],
    model: Annotated[Model, Form()] = config.whisper.model,
    prompt: Annotated[str | None, Form()] = None,
    response_format: Annotated[ResponseFormat, Form()] = config.default_response_format,
    temperature: Annotated[float, Form()] = 0.0,
    stream: Annotated[bool, Form()] = False,
):
    start = time.perf_counter()
    whisper = load_model(model)
    segments, transcription_info = whisper.transcribe(
        file.file,
        task="translate",
        initial_prompt=prompt,
        temperature=temperature,
        vad_filter=True,
    )

    def segment_responses():
        for segment in segments:
            if response_format == ResponseFormat.TEXT:
                yield segment.text
            elif response_format == ResponseFormat.JSON:
                yield TranscriptionJsonResponse.from_segments(
                    [segment]
                ).model_dump_json()
            elif response_format == ResponseFormat.VERBOSE_JSON:
                yield TranscriptionVerboseJsonResponse.from_segment(
                    segment, transcription_info
                ).model_dump_json()

    if not stream:
        segments = list(segments)
        logger.info(
            f"Translated {transcription_info.duration}({transcription_info.duration_after_vad}) seconds of audio in {time.perf_counter() - start:.2f} seconds"
        )
        if response_format == ResponseFormat.TEXT:
            return utils.segments_text(segments)
        elif response_format == ResponseFormat.JSON:
            return TranscriptionJsonResponse.from_segments(segments)
        elif response_format == ResponseFormat.VERBOSE_JSON:
            return TranscriptionVerboseJsonResponse.from_segments(
                segments, transcription_info
            )
    else:
        return StreamingResponse(segment_responses(), media_type="text/event-stream")


# https://platform.openai.com/docs/api-reference/audio/createTranscription
# https://github.com/openai/openai-openapi/blob/master/openapi.yaml#L8915
@app.post("/v1/audio/transcriptions")
def transcribe_file(
    file: Annotated[UploadFile, Form()],
    model: Annotated[Model, Form()] = config.whisper.model,
    language: Annotated[Language | None, Form()] = config.default_language,
    prompt: Annotated[str | None, Form()] = None,
    response_format: Annotated[ResponseFormat, Form()] = config.default_response_format,
    temperature: Annotated[float, Form()] = 0.0,
    timestamp_granularities: Annotated[
        list[Literal["segments"] | Literal["words"]],
        Form(alias="timestamp_granularities[]"),
    ] = ["segments"],
    stream: Annotated[bool, Form()] = False,
):
    start = time.perf_counter()
    whisper = load_model(model)
    segments, transcription_info = whisper.transcribe(
        file.file,
        task="transcribe",
        language=language,
        initial_prompt=prompt,
        word_timestamps="words" in timestamp_granularities,
        temperature=temperature,
        vad_filter=True,
    )

    def segment_responses():
        for segment in segments:
            logger.info(
                f"Transcribed {segment.end - segment.start} seconds of audio in {time.perf_counter() - start:.2f} seconds"
            )
            if response_format == ResponseFormat.TEXT:
                yield segment.text
            elif response_format == ResponseFormat.JSON:
                yield TranscriptionJsonResponse.from_segments(
                    [segment]
                ).model_dump_json()
            elif response_format == ResponseFormat.VERBOSE_JSON:
                yield TranscriptionVerboseJsonResponse.from_segment(
                    segment, transcription_info
                ).model_dump_json()

    if not stream:
        segments = list(segments)
        logger.info(
            f"Transcribed {transcription_info.duration}({transcription_info.duration_after_vad}) seconds of audio in {time.perf_counter() - start:.2f} seconds"
        )
        if response_format == ResponseFormat.TEXT:
            return utils.segments_text(segments)
        elif response_format == ResponseFormat.JSON:
            return TranscriptionJsonResponse.from_segments(segments)
        elif response_format == ResponseFormat.VERBOSE_JSON:
            return TranscriptionVerboseJsonResponse.from_segments(
                segments, transcription_info
            )
    else:
        return StreamingResponse(segment_responses(), media_type="text/event-stream")


async def audio_receiver(ws: WebSocket, audio_stream: AudioStream) -> None:
    try:
        while True:
            bytes_ = await asyncio.wait_for(
                ws.receive_bytes(), timeout=config.max_no_data_seconds
            )
            logger.debug(f"Received {len(bytes_)} bytes of audio data")
            audio_samples = audio_samples_from_file(BytesIO(bytes_))
            audio_stream.extend(audio_samples)
            if audio_stream.duration - config.inactivity_window_seconds >= 0:
                audio = audio_stream.after(
                    audio_stream.duration - config.inactivity_window_seconds
                )
                vad_opts = VadOptions(min_silence_duration_ms=500, speech_pad_ms=0)
                # NOTE: This is a synchronous operation that runs every time new data is received.
                # This shouldn't be an issue unless data is being received in tiny chunks or the user's machine is a potato.
                timestamps = get_speech_timestamps(audio.data, vad_opts)
                if len(timestamps) == 0:
                    logger.info(
                        f"No speech detected in the last {config.inactivity_window_seconds} seconds."
                    )
                    break
                elif (
                    # last speech end time
                    config.inactivity_window_seconds
                    - timestamps[-1]["end"] / SAMPLES_PER_SECOND
                    >= config.max_inactivity_seconds
                ):
                    logger.info(
                        f"Not enough speech in the last {config.inactivity_window_seconds} seconds."
                    )
                    break
    except asyncio.TimeoutError:
        logger.info(
            f"No data received in {config.max_no_data_seconds} seconds. Closing the connection."
        )
    except WebSocketDisconnect as e:
        logger.info(f"Client disconnected: {e}")
    audio_stream.close()


@app.websocket("/v1/audio/transcriptions")
async def transcribe_stream(
    ws: WebSocket,
    model: Annotated[Model, Query()] = config.whisper.model,
    language: Annotated[Language | None, Query()] = config.default_language,
    prompt: Annotated[str | None, Query()] = None,
    response_format: Annotated[
        ResponseFormat, Query()
    ] = config.default_response_format,
    temperature: Annotated[float, Query()] = 0.0,
) -> None:
    await ws.accept()
    transcribe_opts = {
        "language": language,
        "initial_prompt": prompt,
        "temperature": temperature,
        "vad_filter": True,
        "condition_on_previous_text": False,
    }
    whisper = load_model(model)
    asr = FasterWhisperASR(whisper, **transcribe_opts)
    audio_stream = AudioStream()
    async with asyncio.TaskGroup() as tg:
        tg.create_task(audio_receiver(ws, audio_stream))
        async for transcription in audio_transcriber(asr, audio_stream):
            logger.debug(f"Sending transcription: {transcription.text}")
            if ws.client_state == WebSocketState.DISCONNECTED:
                break

            if response_format == ResponseFormat.TEXT:
                await ws.send_text(transcription.text)
            elif response_format == ResponseFormat.JSON:
                await ws.send_json(
                    TranscriptionJsonResponse.from_transcription(
                        transcription
                    ).model_dump()
                )
            elif response_format == ResponseFormat.VERBOSE_JSON:
                await ws.send_json(
                    TranscriptionVerboseJsonResponse.from_transcription(
                        transcription
                    ).model_dump()
                )

    if not ws.client_state == WebSocketState.DISCONNECTED:
        logger.info("Closing the connection.")
        await ws.close()