python - 如何停止将opencv帧流式传输到浏览器

Question

我正在尝试将 opencv 帧流式传输到浏览器。经过研究，我发现了 Miguel 的教程:
https://blog.miguelgrinberg.com/post/video-streaming-with-flask/page/10

让我分解一下我想要实现的目标:在主页上，我尝试使用 opencv 实时流式传输 opencv 帧，而在另一个页面上，我需要使用网络摄像头拍照。

问题:使用 Miguel 的流式传输到浏览器的方式，启动了一个无限线程，在这种情况下，当我想在另一个页面上拍照时不会释放相机。切换回主页，我收到此错误:

VIDEOIO ERROR: V4L2: Pixel format of incoming image is unsupported by OpenCV
Unable to stop the stream: Device or resource busy
video stream started
OpenCV(3.4.1) Error: Assertion failed (scn == 3 || scn == 4) in cvtColor, file /home/eli/cv/opencv-3.4.1/modules/imgproc/src/color.cpp, line 11115
Debugging middleware caught exception in streamed response at a point where response headers were already sent.

这是我的代码:

detect_face_video.py

这是我进行人脸识别的地方

# import the necessary packages
 from imutils.video import VideoStream
 import face_recognition
 import argparse
 import imutils
 import pickle
 import time
 import cv2
 from flask import Flask, render_template, Response
 import sys
 import numpy
 from app.cv_func import draw_box
 import redis
 import datetime
 from app.base_camera import BaseCamera



 import os 


 global red
 red = redis.StrictRedis(host='localhost', port=6379, db=0, decode_responses=True)



class detect_face:



def gen(self):
    i=1
    while i<10:
        yield (b'--frame\r\n'
            b'Content-Type: text/plain\r\n\r\n'+str(i)+b'\r\n')
        i+=1


def get_frame(self):

    dir_path = os.path.dirname(os.path.realpath(__file__))
    # load the known faces and embeddings
    print("[INFO] loading encodings...")
     "rb").read())
    data = pickle.loads(open("%s/encode.pickle"%dir_path, "rb").read())

    # initialize the video stream and pointer to output video file, then
    # allow the camera sensor to warm up
    print("[INFO] starting video stream...")

    try:
        vs = VideoStream(src=1).start()

    except Exception as ex:
        vs.release()



    print("video stream started")


    # loop over frames from the video file stream
    i=1
    counter = 1
    while True:

        # grab the frame from the threaded video stream
        try:
            frame = vs.read()
        except Exception as ex:
            print("an error occured here")
            print(ex)
        # finally:
            continue

        # convert the input frame from BGR to RGB then resize it to have
        # a width of 750px (to speedup processing)
        rgb = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
        rgb = imutils.resize(frame, width=450, height=400)
        r = frame.shape[1] / float(rgb.shape[1])


        # detect the (x, y)-coordinates of the bounding boxes
        # corresponding to each face in the input frame, then compute
        # the facial embeddings for each face
        boxes = face_recognition.face_locations(rgb,
            model="hog")
        # boxes = face_recognition.face_locations(rgb,
        #   model=args["detection_method"])
        encodings = face_recognition.face_encodings(rgb, boxes)
        names = []


        # loop over the facial embeddings

        for encoding in encodings:
            print(encoding)
            # attempt to match each face in the input image to our known
            # encodings
            matches = face_recognition.compare_faces(data["encodings"],
                encoding)
            # matches = face_recognition.compare_faces(data["encodings"],
            #   encoding)
            name = "Unknown"  

            # check to see if we have found a match
            if True in matches:
                # find the indexes of all matched faces then initialize a
                # dictionary to count the total number of times each face
                # was matched
                matchedIdxs = [i for (i, b) in enumerate(matches) if b]
                counts = {}

                # loop over the matched indexes and maintain a count for
                # each recognized face face
                for i in matchedIdxs:
                    name = data["names"][i]
                    counts[name] = counts.get(name, 0) + 1

                # determine the recognized face with the largest number
                # of votes (note: in the event of an unlikely tie Python
                # will select first entry in the dictionary)
                name = max(counts, key=counts.get)

            # update the list of names
            names.append(name)
            red.set('currentName', name)



            # self.create_report(name, counter)
            # f = open("tester.txt", 'w+')
            key='StudentName%d'%counter

            if(name != 'Unknown'):
                red.set(key,name)
            red.set('counter', counter)



            counter+=1

            # loop over the recognized faces
        for ((top, right, bottom, left), name) in zip(boxes, names):
            # rescale the face coordinates
            top = int(top * r)
            right = int(right * r)
            bottom = int(bottom * r)
            left = int(left * r)
            # print("top: %d right: %d bottom: %d left: %d"%(top,right,bottom,left))
            # print("top_: %d right_: %d bottom_: %d left_: %d"%(top_,right_,bottom_,left_))

            # draw the predicted face name on the image
            cv2.rectangle(frame, (left, top), (right, bottom),
                (0, 255, 0), 2)
            # draw_box(frame, int(left/2), int(top/2), int(right/2), int(bottom/2))
            y = top - 15 if top - 15 > 15 else top + 15
            cv2.putText(frame, name, (left, y), cv2.FONT_HERSHEY_SIMPLEX,
                0.75, (0, 255, 0), 2)

        imgencode=cv2.imencode('.jpg',frame)[1]
        stringData = imgencode.tostring()
        yield(b'--frame\r\n'
                b'Content-Type: text/plain\r\n\r\n'+stringData+b'\r\n')
        i+=1

    del(vs)
    cv2.destroyAllWindows()
    vs.stop()

和路由文件(我只粘贴了重要部分):
路线.py

 from flask import Flask, render_template, request,Response,jsonify,make_response
 from app.detect_face_video import detect_face
 detect = detect_face()     


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


 def get_frame_():
    detect.gen()
    detect.get_frame()




 @app.route('/calc')
 def calc():
  #This function displays the video streams in the webpage 

    # detect.vs.stop()
    return Response(detect.get_frame(),mimetype='multipart/x-mixed-replace; boundary=frame')

我如何在离开该页面(主页)时停止或说暂停流？

Answer 1

如果您正在寻找更快、更强大且更简单的方式将帧流式传输到浏览器，那么您可以使用我的 VidGear Python 库的 WebGear ，这是一个强大的 ASGI Video-streamer API，建立在 Starlette 之上- 一个轻量级的 ASGI 异步框架/工具包。
要求:仅适用于 Python 3.6+。

# install VidGear
python3 -m pip install vidgear[asyncio]

然后你可以使用这个完整的 python 示例，它在地址 http://<host-machine ip>:8000/ 上运行视频服务器在网络上的任何浏览器上，只需几行代码:

# import required libraries
import uvicorn
from vidgear.gears.asyncio import WebGear

# various performance tweaks
options = {
    "frame_size_reduction": 40,
    "jpeg_compression_quality": 80,
    "jpeg_compression_fastdct": True,
    "jpeg_compression_fastupsample": False,
}

# initialize WebGear app
web = WebGear(source="foo.mp4", logging=True, **options)

# run this app on Uvicorn server at address http://localhost:8000/
uvicorn.run(web(), host="0.0.0.0", port=8000)

# close app safely
web.shutdown()

Documentation
如果仍然得到一些错误，提出 issue here在其 GitHub 存储库中。