serving_transcription.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
import asyncio
import io
import math
import time
from collections.abc import AsyncGenerator
from math import ceil
from typing import Final, Optional, Union, cast

import numpy as np
from fastapi import Request

from vllm.config import ModelConfig
from vllm.engine.protocol import EngineClient
from vllm.entrypoints.logger import RequestLogger
from vllm.entrypoints.openai.protocol import (
    DeltaMessage, ErrorResponse, RequestResponseMetadata, TranscriptionRequest,
    TranscriptionResponse, TranscriptionResponseStreamChoice,
    TranscriptionStreamResponse, UsageInfo)
from vllm.entrypoints.openai.serving_engine import OpenAIServing
from vllm.entrypoints.openai.serving_models import OpenAIServingModels
from vllm.inputs.data import PromptType
from vllm.logger import init_logger
from vllm.outputs import RequestOutput
from vllm.transformers_utils.processor import cached_get_processor
from vllm.utils import PlaceholderModule

try:
    import librosa
except ImportError:
    librosa = PlaceholderModule("librosa")  # type: ignore[assignment]

logger = init_logger(__name__)

# From https://platform.openai.com/docs/guides/speech-to-text/supported-languages#supported-languages
# TODO these configs should live somewhere with the model so we can support
# additional ones

ISO639_1_SUPPORTED_LANGS = {
    "af": "Afrikaans",
    "ar": "Arabic",
    "hy": "Armenian",
    "az": "Azerbaijani",
    "be": "Belarusian",
    "bs": "Bosnian",
    "bg": "Bulgarian",
    "ca": "Catalan",
    "zh": "Chinese",
    "hr": "Croatian",
    "cs": "Czech",
    "da": "Danish",
    "nl": "Dutch",
    "en": "English",
    "et": "Estonian",
    "fi": "Finnish",
    "fr": "French",
    "gl": "Galician",
    "de": "German",
    "el": "Greek",
    "he": "Hebrew",
    "hi": "Hindi",
    "hu": "Hungarian",
    "is": "Icelandic",
    "id": "Indonesian",
    "it": "Italian",
    "ja": "Japanese",
    "kn": "Kannada",
    "kk": "Kazakh",
    "ko": "Korean",
    "lv": "Latvian",
    "lt": "Lithuanian",
    "mk": "Macedonian",
    "ms": "Malay",
    "mr": "Marathi",
    "mi": "Maori",
    "ne": "Nepali",
    "no": "Norwegian",
    "fa": "Persian",
    "pl": "Polish",
    "pt": "Portuguese",
    "ro": "Romanian",
    "ru": "Russian",
    "sr": "Serbian",
    "sk": "Slovak",
    "sl": "Slovenian",
    "es": "Spanish",
    "sw": "Swahili",
    "sv": "Swedish",
    "tl": "Tagalog",
    "ta": "Tamil",
    "th": "Thai",
    "tr": "Turkish",
    "uk": "Ukrainian",
    "ur": "Urdu",
    "vi": "Vietnamese",
    "cy": "Welsh"
}
ISO639_1_OTHER_LANGS = {
    "lo": "Lao",
    "jw": "Javanese",
    "tk": "Turkmen",
    "yi": "Yiddish",
    "so": "Somali",
    "bn": "Bengali",
    "nn": "Norwegian Nynorsk",
    "si": "Sinhala",
    "yo": "Yoruba",
    "sa": "Sanskrit",
    "mi": "Māori",
    "fo": "Faroese",  # codespell:ignore
    "mt": "Maltese",
    "tg": "Tajik",
    "mg": "Malagasy",
    "haw": "Hawaiian",
    "km": "Khmer",
    "br": "Breton",
    "ps": "Pashto",
    "ln": "Lingala",
    "la": "Latin",
    "ml": "Malayalam",
    "sq": "Albanian",
    "su": "Sundanese",
    "eu": "Basque",
    "ka": "Georgian",
    "uz": "Uzbek",
    "sn": "Shona",
    "ht": "Haitian",
    "as": "Assamese",
    "mn": "Mongolian",
    "te": "Telugu",
    "pa": "Panjabi",
    "tt": "Tatar",
    "gu": "Gujarati",
    "oc": "Occitan",
    "ha": "Hausa",
    "ba": "Bashkir",
    "my": "Burmese",
    "sd": "Sindhi",
    "am": "Amharic",
    "lb": "Luxembourgish",
    "bo": "Tibetan"
}

# As per https://platform.openai.com/docs/guides/speech-to-text#overview.
# TODO configurable
MAX_AUDIO_CLIP_FILESIZE_MB = 25
OVERLAP_CHUNK_SECOND = 1
MIN_ENERGY_WINDOW_SIZE = 1600  # 1600 ~ 100ms for 16000 Hz audio


class OpenAIServingTranscription(OpenAIServing):

    def __init__(
        self,
        engine_client: EngineClient,
        model_config: ModelConfig,
        models: OpenAIServingModels,
        *,
        request_logger: Optional[RequestLogger],
        return_tokens_as_token_ids: bool = False,
    ):
        super().__init__(engine_client=engine_client,
                         model_config=model_config,
                         models=models,
                         request_logger=request_logger,
                         return_tokens_as_token_ids=return_tokens_as_token_ids)

        self.default_sampling_params = (
            self.model_config.get_diff_sampling_param())
        processor = cached_get_processor(model_config.model)
        self.max_audio_clip_s = processor.feature_extractor.chunk_length
        self.model_sr = processor.feature_extractor.sampling_rate
        self.hop_length = processor.feature_extractor.hop_length

        if self.default_sampling_params:
            logger.info(
                "Overwriting default completion sampling param with: %s",
                self.default_sampling_params)

    async def _preprocess_transcription(
        self,
        request: TranscriptionRequest,
        audio_data: bytes,
    ) -> tuple[list[PromptType], float]:
        # Validate request
        # TODO language should be optional and can be guessed.
        # For now we default to en. See
        # https://github.com/huggingface/transformers/blob/main/src/transformers/models/whisper/generation_whisper.py#L1520
        lang_token = f"<|{request.language}|>" if request.language else "<|en|>"
        if request.language:
            if request.language in ISO639_1_SUPPORTED_LANGS:
                pass
            elif request.language in ISO639_1_OTHER_LANGS:
                logger.warning(
                    "The selected language %s has limited accuracy with"
                    " reported WER>=0.5. Results may be less accurate "
                    "for this choice.", request.language)
            else:
                raise ValueError(
                    f"Unsupported language: {request.language}."
                    "Language should be one of:" +
                    f" {list(ISO639_1_SUPPORTED_LANGS.values())}" +
                    f"or {list(ISO639_1_OTHER_LANGS.values())}")

        if len(audio_data) / 1024**2 > MAX_AUDIO_CLIP_FILESIZE_MB:
            raise ValueError("Maximum file size exceeded.")

        with io.BytesIO(audio_data) as bytes_:
            y, sr = librosa.load(bytes_)

        duration = librosa.get_duration(y=y, sr=sr)
        chunks = [y] if duration < 30 else self._split_audio(y, sr)
        prompts = []
        for i, chunk in enumerate(chunks):
            prompt = {
                "encoder_prompt": {
                    "prompt": "",
                    "multi_modal_data": {
                        "audio": (chunk, sr),
                    },
                },
                "decoder_prompt":
                f"<|startoftranscript|>{lang_token}<|transcribe|><|notimestamps|>{request.prompt}"
                if i == 0 else ""
            }
            prompts.append(cast(PromptType, prompt))
        return prompts, duration

    # TODO (varun) : Make verbose response work !
    async def create_transcription(
        self, audio_data: bytes, request: TranscriptionRequest,
        raw_request: Request
    ) -> Union[TranscriptionResponse, AsyncGenerator[str, None],
               ErrorResponse]:
        """Transcription API similar to OpenAI's API.

        See https://platform.openai.com/docs/api-reference/audio/createTranscription
        for the API specification. This API mimics the OpenAI transcription API.
        """
        error_check_ret = await self._check_model(request)
        if error_check_ret is not None:
            return error_check_ret

        # If the engine is dead, raise the engine's DEAD_ERROR.
        # This is required for the streaming case, where we return a
        # success status before we actually start generating text :).
        if self.engine_client.errored:
            raise self.engine_client.dead_error

        if request.response_format not in ['text', 'json']:
            return self.create_error_response(
                "Currently only support response_format `text` or `json`")

        request_id = f"trsc-{self._base_request_id(raw_request)}"

        request_metadata = RequestResponseMetadata(request_id=request_id)
        if raw_request:
            raw_request.state.request_metadata = request_metadata

        try:
            (
                lora_request,
                prompt_adapter_request,
            ) = self._maybe_get_adapters(request)

            if lora_request:
                return self.create_error_response(
                    "Currently do not support LoRA for Transcription.")
            if prompt_adapter_request:
                return self.create_error_response(
                    "Currently do not support PromptAdapter for Transcription."
                )

            prompts, duration_s = await self._preprocess_transcription(
                request=request,
                audio_data=audio_data,
            )

        except ValueError as e:
            logger.exception("Error in preprocessing prompt inputs")
            return self.create_error_response(str(e))

        list_result_generator: Optional[list[AsyncGenerator[RequestOutput,
                                                            None]]] = None
        try:
            # Unlike most decoder-only models, whisper generation length is not
            # constrained by the size of the input audio, which is mapped to a
            # fixed-size log-mel-spectogram.
            default_max_tokens = self.model_config.max_model_len
            sampling_params = request.to_sampling_params(
                default_max_tokens, self.default_sampling_params)

            self._log_inputs(
                request_id,
                prompts[0]['decoder_prompt'],  # type: ignore
                params=sampling_params,
                lora_request=None,
                prompt_adapter_request=None)

            list_result_generator = [
                self.engine_client.generate(
                    prompt,
                    sampling_params,
                    request_id,
                ) for prompt in prompts
            ]
        except ValueError as e:
            # TODO: Use a vllm-specific Validation Error
            return self.create_error_response(str(e))

        if request.stream:
            return self.transcription_stream_generator(request,
                                                       list_result_generator,
                                                       request_id,
                                                       request_metadata,
                                                       duration_s)
        # Non-streaming response.
        try:
            assert list_result_generator is not None
            text = ""
            for result_generator in list_result_generator:
                async for op in result_generator:
                    text += op.outputs[0].text
            return TranscriptionResponse(text=text)
        except asyncio.CancelledError:
            return self.create_error_response("Client disconnected")
        except ValueError as e:
            # TODO: Use a vllm-specific Validation Error
            return self.create_error_response(str(e))

    async def transcription_stream_generator(
            self, request: TranscriptionRequest,
            list_result_generator: list[AsyncGenerator[RequestOutput, None]],
            request_id: str, request_metadata: RequestResponseMetadata,
            audio_duration_s: float) -> AsyncGenerator[str, None]:
        created_time = int(time.time())
        model_name = request.model
        chunk_object_type: Final = "transcription.chunk"

        completion_tokens = 0
        num_prompt_tokens = 0

        include_usage = request.stream_include_usage \
            if request.stream_include_usage else False
        include_continuous_usage = request.stream_continuous_usage_stats\
            if include_usage and request.stream_continuous_usage_stats\
            else False

        try:
            for result_generator in list_result_generator:
                async for res in result_generator:
                    # On first result.
                    if res.prompt_token_ids is not None:
                        # Do not account the 4-tokens `<|startoftranscript|>..`
                        # Could be negative when language token
                        # is not specified.
                        num_prompt_tokens = max(
                            len(res.prompt_token_ids) - 4, 0)
                        # NOTE(NickLucche) user can't pass encoder
                        # prompts directly at least not to Whisper.
                        # One indicator of the encoder amount of processing
                        # is the log-mel spectogram length.
                        num_prompt_tokens += ceil(
                            audio_duration_s * self.model_sr / self.hop_length)

                    # We need to do it here, because if there are exceptions in
                    # the result_generator, it needs to be sent as the FIRST
                    # response (by the try...catch).

                    # Just one output (n=1) supported.
                    assert len(res.outputs) == 1
                    output = res.outputs[0]

                    delta_message = DeltaMessage(content=output.text)
                    completion_tokens += len(output.token_ids)

                    if output.finish_reason is None:
                        # Still generating, send delta update.
                        choice_data = TranscriptionResponseStreamChoice(
                            delta=delta_message)
                    else:
                        # Model is finished generating.
                        choice_data = TranscriptionResponseStreamChoice(
                            delta=delta_message,
                            finish_reason=output.finish_reason,
                            stop_reason=output.stop_reason)

                    chunk = TranscriptionStreamResponse(
                        id=request_id,
                        object=chunk_object_type,
                        created=created_time,
                        choices=[choice_data],
                        model=model_name)

                    # handle usage stats if requested & if continuous
                    if include_continuous_usage:
                        chunk.usage = UsageInfo(
                            prompt_tokens=num_prompt_tokens,
                            completion_tokens=completion_tokens,
                            total_tokens=num_prompt_tokens + completion_tokens,
                        )

                    data = chunk.model_dump_json(exclude_unset=True)
                    yield f"data: {data}\n\n"

            # Once the final token is handled, if stream_options.include_usage
            # is sent, send the usage.
            if include_usage:
                final_usage = UsageInfo(prompt_tokens=num_prompt_tokens,
                                        completion_tokens=completion_tokens,
                                        total_tokens=num_prompt_tokens +
                                        completion_tokens)

                final_usage_chunk = TranscriptionStreamResponse(
                    id=request_id,
                    object=chunk_object_type,
                    created=created_time,
                    choices=[],
                    model=model_name,
                    usage=final_usage)
                final_usage_data = (final_usage_chunk.model_dump_json(
                    exclude_unset=True, exclude_none=True))
                yield f"data: {final_usage_data}\n\n"

            # report to FastAPI middleware aggregate usage across all choices
            request_metadata.final_usage_info = UsageInfo(
                prompt_tokens=num_prompt_tokens,
                completion_tokens=completion_tokens,
                total_tokens=num_prompt_tokens + completion_tokens)

        except Exception as e:
            # TODO: Use a vllm-specific Validation Error
            logger.exception("Error in chat completion stream generator.")
            data = self.create_streaming_error_response(str(e))
            yield f"data: {data}\n\n"
        # Send the final done message after all response.n are finished
        yield "data: [DONE]\n\n"

    def _split_audio(self, audio_data: np.ndarray,
                     sample_rate: int) -> list[np.ndarray]:
        chunk_size = sample_rate * self.max_audio_clip_s
        overlap_size = sample_rate * OVERLAP_CHUNK_SECOND
        chunks = []
        i = 0
        while i < audio_data.shape[-1]:
            if i + chunk_size >= audio_data.shape[-1]:
                # handle last chunk
                chunks.append(audio_data[..., i:])
                break

            # Find the best split point in the overlap region
            search_start = i + chunk_size - overlap_size
            search_end = min(i + chunk_size, audio_data.shape[-1])
            split_point = self._find_split_point(audio_data, search_start,
                                                 search_end)

            # Extract chunk up to the split point
            chunks.append(audio_data[..., i:split_point])
            i = split_point
        return chunks

    def _find_split_point(self, wav: np.ndarray, start_idx: int,
                          end_idx: int) -> int:
        """Find the best point to split audio by 
        looking for silence or low amplitude.
        Args:
            wav: Audio tensor [1, T]
            start_idx: Start index of search region
            end_idx: End index of search region
        Returns:
            Index of best splitting point
        """
        segment = wav[start_idx:end_idx]

        # Calculate RMS energy in small windows
        min_energy = math.inf
        quietest_idx = 0
        for i in range(0,
                       len(segment) - MIN_ENERGY_WINDOW_SIZE,
                       MIN_ENERGY_WINDOW_SIZE):
            window = segment[i:i + MIN_ENERGY_WINDOW_SIZE]
            energy = (window**2).mean()**0.5
            if energy < min_energy:
                quietest_idx = i + start_idx
                min_energy = energy
        return quietest_idx