PaddleSpeech/paddlespeech/server/ws/asr_socket.py

# Copyright (c) 2022 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import json

from fastapi import APIRouter
from fastapi import WebSocket
from fastapi import WebSocketDisconnect
from starlette.websockets import WebSocketState as WebSocketState

from paddlespeech.server.engine.asr.online.asr_engine import PaddleASRConnectionHanddler
from paddlespeech.server.engine.engine_pool import get_engine_pool

router = APIRouter()


@router.websocket('/paddlespeech/asr/streaming')
async def websocket_endpoint(websocket: WebSocket):
    """PaddleSpeech Online ASR Server api

    Args:
        websocket (WebSocket): the websocket instance
    """

    #1. the interface wait to accept the websocket protocal header
    #   and only we receive the header, it establish the connection with specific thread
    await websocket.accept()

    #2. if we accept the websocket headers, we will get the online asr engine instance
    engine_pool = get_engine_pool()
    asr_engine = engine_pool['asr']

    #3. each websocket connection, we will create an PaddleASRConnectionHanddler to process such audio
    #   and each connection has its own connection instance to process the request
    #   and only if client send the start signal, we create the PaddleASRConnectionHanddler instance
    connection_handler = None

    try:
        #4. we do a loop to process the audio package by package according the protocal
        #   and only if the client send finished signal, we will break the loop
        while True:
            # careful here, changed the source code from starlette.websockets
            # 4.1 we wait for the client signal for the specific action
            assert websocket.application_state == WebSocketState.CONNECTED
            message = await websocket.receive()
            websocket._raise_on_disconnect(message)

            #4.2 text for the action command and bytes for pcm data
            if "text" in message:
                # we first parse the specific command
                message = json.loads(message["text"])
                if 'signal' not in message:
                    resp = {"status": "ok", "message": "no valid json data"}
                    await websocket.send_json(resp)

                # start command, we create the PaddleASRConnectionHanddler instance to process the audio data
                # end command, we process the all the last audio pcm and return the final result
                #              and we break the loop
                if message['signal'] == 'start':
                    resp = {"status": "ok", "signal": "server_ready"}
                    # do something at begining here
                    # create the instance to process the audio
                    connection_handler = PaddleASRConnectionHanddler(asr_engine)
                    await websocket.send_json(resp)
                elif message['signal'] == 'end':
                    # reset single  engine for an new connection
                    # and we will destroy the connection
                    connection_handler.decode(is_finished=True)
                    connection_handler.rescoring()
                    asr_results = connection_handler.get_result()
                    connection_handler.reset()

                    resp = {
                        "status": "ok",
                        "signal": "finished",
                        'result': asr_results
                    }
                    await websocket.send_json(resp)
                    break
                else:
                    resp = {"status": "ok", "message": "no valid json data"}
                    await websocket.send_json(resp)
            elif "bytes" in message:
                # bytes for the pcm data
                message = message["bytes"]

                # we extract the remained audio pcm 
                # and decode for the result in this package data
                connection_handler.extract_feat(message)
                connection_handler.decode(is_finished=False)
                asr_results = connection_handler.get_result()

                # return the current period result
                # if the engine create the vad instance, this connection will have many period results 
                resp = {'result': asr_results}
                await websocket.send_json(resp)
    except WebSocketDisconnect:
        pass