javascript - 如何将实时视频帧从客户端流式传输到 Flask 服务器并返回客户端？

Question

我正在尝试构建一个客户端服务器架构，在其中使用 getUserMedia() 从用户的网络摄像头捕获实时视频。现在不再直接在 <video> 中显示视频标签，我想将它发送到我的 flask 服务器，对框架进行一些处理并将其扔回我的网页。

我使用了 socketio 来创建客户端-服务器连接。这是我的 index.html 中的脚本。请原谅我的错误或任何错误的代码。

<div id="container">
    <video autoplay="true" id="videoElement">

    </video>
</div>

<script type="text/javascript" charset="utf-8">

    var socket = io('http://127.0.0.1:5000');

    // checking for connection
    socket.on('connect', function(){
      console.log("Connected... ", socket.connected)
    });

    var video = document.querySelector("#videoElement");


    // asking permission to access the system camera of user, capturing live 
    // video on getting true.

    if (navigator.mediaDevices.getUserMedia) {
      navigator.mediaDevices.getUserMedia({ video: true })
        .then(function (stream) {

          // instead of showing it directly in <video>, I want to send these frame to server

          //video_t.srcObject = stream

          //this code might be wrong, but this is what I want to do.
          socket.emit('catch-frame', { image: true, buffer: getFrame() });
        })
        .catch(function (err0r) {
          console.log(err0r)
          console.log("Something went wrong!");
        });
    }

    // returns a frame encoded in base64
    const getFrame = () => {
        const canvas = document.createElement('canvas');
        canvas.width = video_t.videoWidth;
        canvas.height = video_t.videoHeight;
        canvas.getContext('2d').drawImage(video_t, 0, 0);
        const data = canvas.toDataURL('image/png');
        return data;
    }


    // receive the frame from the server after processed and now I want display them in either 
    // <video> or <img>
    socket.on('response_back', function(frame){

      // this code here is wrong, but again this is what something I want to do.
      video.srcObject = frame;
    });

</script>

在我的app.py中 -

from flask import Flask, render_template
from flask_socketio import SocketIO, emit

app = Flask(__name__)
socketio = SocketIO(app)

@app.route('/', methods=['POST', 'GET'])
def index():
    return render_template('index.html')

@socketio.on('catch-frame')
def catch_frame(data):

    ## getting the data frames

    ## do some processing 

    ## send it back to client
    emit('response_back', data)  ## ??


if __name__ == '__main__':
    socketio.run(app, host='127.0.0.1')

我也想过通过 WebRTC 来做到这一点，但我只获取点对点的代码。

那么，有人可以帮我解决这个问题吗？预先感谢您的帮助。

Answer 1

所以，我想做的是获取客户端网络摄像头捕获的实时视频流并在后端处理它们。

我的后端代码是用 Python 编写的，我使用 SocketIo 将帧从前端发送到后端。您可以看一下这个设计，以更好地了解正在发生的事情 - image

1. 我的服务器(app.py)将在后端运行，客户端将访问index.html
2. SocketIo 连接将建立，使用网络摄像头捕获的视频流将逐帧发送到服务器。
3. 这些帧随后将在后端进行处理并发送回客户端。
4. 来自服务器的已处理帧可以显示在 img 标签中。

这是工作代码-

app.py

@socketio.on('image')
def image(data_image):
    sbuf = StringIO()
    sbuf.write(data_image)

    # decode and convert into image
    b = io.BytesIO(base64.b64decode(data_image))
    pimg = Image.open(b)

    ## converting RGB to BGR, as opencv standards
    frame = cv2.cvtColor(np.array(pimg), cv2.COLOR_RGB2BGR)

    # Process the image frame
    frame = imutils.resize(frame, width=700)
    frame = cv2.flip(frame, 1)
    imgencode = cv2.imencode('.jpg', frame)[1]

    # base64 encode
    stringData = base64.b64encode(imgencode).decode('utf-8')
    b64_src = 'data:image/jpg;base64,'
    stringData = b64_src + stringData

    # emit the frame back
    emit('response_back', stringData)

index.html

<div id="container">
    <canvas id="canvasOutput"></canvas>
    <video autoplay="true" id="videoElement"></video>
</div>

<div class = 'video'>
    <img id="image">
</div>

<script>
    var socket = io('http://localhost:5000');

    socket.on('connect', function(){
        console.log("Connected...!", socket.connected)
    });

    const video = document.querySelector("#videoElement");

    video.width = 500; 
    video.height = 375; ;

    if (navigator.mediaDevices.getUserMedia) {
        navigator.mediaDevices.getUserMedia({ video: true })
        .then(function (stream) {
            video.srcObject = stream;
            video.play();
        })
        .catch(function (err0r) {
            console.log(err0r)
            console.log("Something went wrong!");
        });
    }

    let src = new cv.Mat(video.height, video.width, cv.CV_8UC4);
    let dst = new cv.Mat(video.height, video.width, cv.CV_8UC1);
    let cap = new cv.VideoCapture(video);

    const FPS = 22;

    setInterval(() => {
        cap.read(src);

        var type = "image/png"
        var data = document.getElementById("canvasOutput").toDataURL(type);
        data = data.replace('data:' + type + ';base64,', ''); //split off junk 
        at the beginning

        socket.emit('image', data);
    }, 10000/FPS);


    socket.on('response_back', function(image){
        const image_id = document.getElementById('image');
        image_id.src = image;
    });

</script>

此外，Websockets 在安全源上运行。