如何使用Opencv和Flask将网络摄像头图像流广播到多个设备？

Question

我有以下代码。当尝试用一个设备连接服务器时，它能够正常工作。但是当两个设备连接时，只有一个设备能够工作，另一个设备会出现下面的错误。

目标是将视频流广播到多个设备上。此外，是否有办法通过Flask来提高传输帧率并减少延迟？

CODE

Camera.py

import cv2

class VideoCamera(object):
    def __init__(self):
        # Using OpenCV to capture from device 0. If you have trouble capturing
        # from a webcam, comment the line below out and use a video file
        # instead.
        self.video = cv2.VideoCapture(0)
        # If you decide to use video.mp4, you must have this file in the folder
        # as the main.py.
        # self.video = cv2.VideoCapture('video.mp4')

    def __del__(self):
        self.video.release()

    def get_frame(self):
        success, image = self.video.read()
        # We are using Motion JPEG, but OpenCV defaults to capture raw images,
        # so we must encode it into JPEG in order to correctly display the
        # video stream.
        ret, jpeg = cv2.imencode('.jpg', image)
        return jpeg.tobytes()

Main.py

import os

install_opencv = os.system("pip install flask opencv-python")
print("Install OPENCV-PYTHON: ", install_opencv)


from flask import Flask, render_template, Response
from camera import VideoCamera

app = Flask(__name__)

@app.route('/')
def index():
    return render_template('index.html')

def gen(camera):
    while True:
        frame = camera.get_frame()
        yield (b'--frame\r\n'
               b'Content-Type: image/jpeg\r\n\r\n' + frame + b'\r\n\r\n')

@app.route('/video_feed')
def video_feed():
    return Response(gen(VideoCamera()),
                    mimetype='multipart/x-mixed-replace; boundary=frame')

if __name__ == '__main__':
    app.run(host='0.0.0.0', debug=True)

错误

Traceback (most recent call last):
cv2.error: OpenCV(3.4.3) C:\projects\opencv-python\opencv\modules\imgcodecs\src\grfmt_base.cpp:145: error: (-10:Unknown error code -10) Raw image encoder error: Empty JPEG image (DNL not supported) in function 'cv::BaseImageEncoder::throwOnEror'
127.0.0.1 - - [01/Nov/2018 16:16:21] "GET /video_feed HTTP/1.1" 200

- Ruben A. Chevez

Answer 1

我也尝试了这种方法，但无法在两个设备上访问。

在Github上有一个项目https://github.com/miguelgrinberg/flask-video-streaming，或者您可以在开发者的网站上看到更好的解释https://blog.miguelgrinberg.com/post/flask-video-streaming-revisited #commentform

使用这段代码，我能够从多个设备访问，但只允许显示一个摄像头。我正在努力使其能够查看2个或更多摄像头，就像是一个DVR一样。

- Márcio