Question

我已经设置了一个IP摄像机，并且可以浏览到其IP并获取MJPEG流，我试图逐帧下载它，以便可以在另一台服务器上分析图像。但是我在阅读流时遇到了麻烦。我的代码是：

import cv2
import urllib.request
import numpy as np
import ssl

ctx = ssl.create_default_context()
ctx.check_hostname = False
ctx.verify_mode = ssl.CERT_NONE       

stream = urllib.request.urlopen('https://x.x.x.x:8602/Interface/Cameras/GetJPEGStream?Camera=Bosch%20NBE6502AL%20Bullet&ResponseFormat=XML&AuthUser=username&AuthPass=password',context=ctx)
bytes = ''
while True:
    bytes += stream.read(1024)
    a = bytes.find('\xff\xd8')
    b = bytes.find('\xff\xd9')
    if a != -1 and b != -1:
        jpg = bytes[a:b+2]
        bytes = bytes[b+2:]
        i = cv2.imdecode(np.fromstring(jpg, dtype=np.uint8), cv2.CV_LOAD_IMAGE_COLOR)
        cv2.imshow('i', i)
        if cv2.waitKey(1) == 27:
            exit(0)

它给我以下错误：

Traceback (most recent call last):
File "mjpeg.py", line 15, in <module>
bytes += stream.read(1024)
TypeError: can only concatenate str (not "bytes") to str

我认为流输出字符串，但是如何将流转换为字节并保存文件呢？

亲切的问候，

艾伦斯

Answer 1

您需要始终bytes，所以将bytes（作为内建类型的名称也是最好的名称）初始化为字节串，然后使用字节文字以查找开始/结束标记：

bytes = b''
while True:
    bytes += stream.read(1024)
    a = bytes.find(b'\xff\xd8')
    b = bytes.find(b'\xff\xd9')
    if a != -1 and b != -1:
        # ...

Answer 2

初始化后（字节=”），而不是（字节= b ''），您的字节变量为str，请更改

stream = urllib.request.urlopen('https://x.x.x.x:8602/Interface/Cameras/GetJPEGStream?Camera=Bosch%20NBE6502AL%20Bullet&ResponseFormat=XML&AuthUser=username&AuthPass=password',context=ctx)
bytes = ''
while True:

对此

stream = urllib.request.urlopen('https://x.x.x.x:8602/Interface/Cameras/GetJPEGStream?Camera=Bosch%20NBE6502AL%20Bullet&ResponseFormat=XML&AuthUser=username&AuthPass=password',context=ctx)
bytes = b''
while True:

您可以像这样检查自己

>>> type('') == type(b'')
False
>>> type(''),type(b'')
(<class 'str'>, <class 'bytes'>)

Answer 3

concatenation仅适用于

相同类型的值

string with a string str += str
bytes with a bytes bytes += bytes

因此将您的bytes变量设置为bytes = b''。希望一切正常。

import cv2
import urllib.request
import numpy as np
import ssl

ctx = ssl.create_default_context()
ctx.check_hostname = False
ctx.verify_mode = ssl.CERT_NONE       

stream = urllib.request.urlopen('https://x.x.x.x:8602/Interface/Cameras/GetJPEGStream?Camera=Bosch%20NBE6502AL%20Bullet&ResponseFormat=XML&AuthUser=username&AuthPass=password',context=ctx)
bytes = b''# MAKE IT BYTES
while True:
    bytes += stream.read(1024)
    a = bytes.find('\xff\xd8')
    b = bytes.find('\xff\xd9')
    if a != -1 and b != -1:
        jpg = bytes[a:b+2]
        bytes = bytes[b+2:]
        i = cv2.imdecode(np.fromstring(jpg, dtype=np.uint8), cv2.CV_LOAD_IMAGE_COLOR)
        cv2.imshow('i', i)
        if cv2.waitKey(1) == 27:
            exit(0)

逐帧下载MJPEG流

3 个答案: