OpenCV 交错视频的帧计数错误，解决方法吗？

Question

使用来自QueryFrame如何工作？的代码示例我注意到，如果程序运行到视频末尾，则需要花费大量时间来退出。我想在最后一帧快速退出，并且我验证了如果我不尝试播放到视频末尾，速度会快很多，但有一些细节对我来说没有意义。这是我的代码：

import cv2

# create a window
winname = "myWindow"
win = cv2.namedWindow(winname, cv2.CV_WINDOW_AUTOSIZE)

# load video file
invideo = cv2.VideoCapture("video.mts")
frames = invideo.get(cv2.cv.CV_CAP_PROP_FRAME_COUNT)
print "frame count:", frames

# interval between frame in ms.
fps = invideo.get(cv2.cv.CV_CAP_PROP_FPS)
interval = int(1000.0 / fps)   

# play video
while invideo.get(cv2.cv.CV_CAP_PROP_POS_FRAMES) < frames:
    print "Showing frame number:", invideo.get(cv2.cv.CV_CAP_PROP_POS_FRAMES)
    (ret, im) = invideo.read()
    if not ret:
        break
    cv2.imshow(winname, im)
    if cv2.waitKey(interval) == 27: # ASCII 27 is the ESC key
        break

del invideo
cv2.destroyWindow(winname)

唯一的问题是，返回的帧数是 744，而最后播放的帧数是 371（从 0 开始计数，所以是 372 帧）。我认为这是因为视频是隔行扫描的，我想我需要考虑到这一点，并将

interval

除以 2，将

frames

除以 2。但问题是，我如何知道我需要这样做？似乎没有属性可以检查这个：

http://docs.opencv.org/modules/highgui/doc/reading_and_writing_images_and_video.html#videocapture-get

Answer 1

我在另一个问题之间写了一些东西，我想我也应该在这里发布它，如果你在Linux上运行，这可能有用，到目前为止它对我有用：

import subprocess
import re

inputVideo = "theFileInQuestion.mp4" # sample of interlaced video

# construct the ffmpeg command as a list of arguments
ffmpegCommand = [
    "ffmpeg", # command for ffmpeg, you need to install this with sudo apt instlal ffmpeg
    "-filter:v", "idet", # filter this specific information
    "-frames:v", "100", # test on first 100 frames
    "-an", # don't test audio
    "-f", "rawvideo", "-y", "/dev/null", # assign results to nothing
    "-i", inputVideo # on this video
]

try:
    outputBytes = subprocess.check_output(ffmpegCommand, stderr=subprocess.STDOUT) # get the output
    outputStr = outputBytes.decode('utf-8') # decode the output
    tffLines = re.findall(r'TFF:\s+(\d+)', outputStr) # search for a pattern that is the count of top field first 
    bffLines = re.findall(r'BFF:\s+(\d+)', outputStr) # search for a pattern that is the count of  bottom field first
    totalInterlacedFrames = sum(map(int, tffLines)) + sum(map(int, bffLines)) # get total interlaced frames in the 100 checked
    if totalInterlacedFrames != 0: # check if interlaced
        print("This video is interlaced!") # YES
    else: # if not
        print("This video is not interlaced!") # NO
except subprocess.CalledProcessError as e:
    print(f"Error during interlacing analysis: {e}")

我主要使用了here描述的linux功能。我也在努力寻找任何 opencv 道具来自动识别隔行扫描。