如何在Windows上从ffmpeg到python同时获取实时视频帧和时间戳

搜索OpenCV的替代方案不会为我的计算机视觉算法中需要的实时摄像机流(在 Windows上)提供时间戳,我发现了ffmpeg和这篇优秀的文章 https://zulko.github.io/blog/2013/09/27/read-and-write-video-frames-in-python-using-ffmpeg/
该解决方案使用ffmpeg,访问其标准输出(stdout)流.我将其扩展为读取标准错误(stderr)流.

在Windows上处理python代码,同时我收到来自ffmpeg stdout的视频帧,但是stderr在为第一帧提供showinfo videofilter详细信息(时间戳)后冻结.

我记得在某个地方的ffmpeg论坛上看到重定向时会绕过像showinfo这样的视频过滤器.这是为什么以下代码无法按预期工作的原因？

预期：它应该将视频帧写入磁盘以及打印时间戳详细信息.
实际：它写入视频文件但没有获取时间戳(showinfo)详细信息.

这是我试过的代码：

import subprocess as sp
import numpy
import cv2

command = [ 'ffmpeg','-i','e:sample.wmv','-pix_fmt','rgb24','-vcodec','rawvideo','-vf','showinfo',# video filter - showinfo will provide frame timestamps
            '-an','-sn',#-an,-sn disables audio and sub-title processing respectively
            '-f','image2pipe','-'] # we need to output to a pipe

pipe = sp.Popen(command,stdout = sp.PIPE,stderr = sp.PIPE) # TODO someone on ffmpeg forum said video filters (e.g. showinfo) are bypassed when stdout is redirected to pipes??? 

for i in range(10):
    raw_image = pipe.stdout.read(1280*720*3)
    img_info = pipe.stderr.read(244) # 244 characters is the current output of showinfo video filter
    print "showinfo output",img_info
    image1 =  numpy.fromstring(raw_image,dtype='uint8')
    image2 = image1.reshape((720,1280,3))  

    # write video frame to file just to verify
    videoFrameName = 'Video_Frame{0}.png'.format(i)
    cv2.imwrite(videoFrameName,image2)

    # throw away the data in the pipe's buffer.
    pipe.stdout.flush()
    pipe.stderr.flush()

那么如何将帧时间戳从ffmpeg转换为python代码,以便可以在我的计算机视觉算法中使用…

import moviepy.editor as mpy

vid = mpy.VideoFileClip('e:sample.wmv')
for timestamp,raw_img in vid.iter_frames(with_times=True):
    # do stuff