在 Python 中将视频转换为帧 - 1 FPS

Question

我有一个 30 fps 的视频。 我需要以 1 FPS 的速度从视频中提取帧。这在 Python 中如何实现？

我有以下从网上获得的代码，但我不确定它是否以 1 FPS 提取帧。 请帮忙！

# Importing all necessary libraries 
import cv2 
import os 
  
# Read the video from specified path 
cam = cv2.VideoCapture("C:\\Users\\Admin\\PycharmProjects\\project_1\\openCV.mp4") 
  
try: 
      
    # creating a folder named data 
    if not os.path.exists('data'): 
        os.makedirs('data') 
  
# if not created then raise error 
except OSError: 
    print ('Error: Creating directory of data') 
  
# frame 
currentframe = 0
  
while(True): 
      
    # reading from frame 
    ret,frame = cam.read() 
  
    if ret: 
        # if video is still left continue creating images 
        name = './data/frame' + str(currentframe) + '.jpg'
        print ('Creating...' + name) 
  
        # writing the extracted images 
        cv2.imwrite(name, frame) 
  
        # increasing counter so that it will 
        # show how many frames are created 
        currentframe += 1
    else: 
        break
  
# Release all space and windows once done 
cam.release() 
cv2.destroyAllWindows()

Answer 1

KPS = 1# Target Keyframes Per Second
VIDEO_PATH = "video1.avi"#"path/to/video/folder" # Change this
IMAGE_PATH = "images/"#"path/to/image/folder" # ...and this 
EXTENSION = ".png"
cap = cv2.VideoCapture(VIDEO_PATH)
fps = round(cap.get(cv2.CAP_PROP_FPS))
print(fps)
# exit()
hop = round(fps / KPS)
curr_frame = 0
while(True):
    ret, frame = cap.read()
ifnot ret: break
if curr_frame % hop == 0:
        name = IMAGE_PATH + "_" + str(curr_frame) + EXTENSION
        cv2.imwrite(name, frame)
    curr_frame += 1
cap.release()

Answer 2

这是我需要从视频中提取帧时使用的代码：

# pip install opencv-python

import cv2
import numpy as np

# video.mp4 is a video of 9 seconds
filename = "video.mp4"

cap = cv2.VideoCapture(filename)
cap.set(cv2.CAP_PROP_POS_AVI_RATIO,0)
frameCount = int(cap.get(cv2.CAP_PROP_FRAME_COUNT))
frameWidth = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
frameHeight = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
videoFPS = int(cap.get(cv2.CAP_PROP_FPS))

print (f"frameCount: {frameCount}")
print (f"frameWidth: {frameWidth}")
print (f"frameHeight: {frameHeight}")
print (f"videoFPS: {videoFPS}")

buf = np.empty((
    frameCount,
    frameHeight,
    frameWidth,
    3), np.dtype('uint8'))

fc = 0
ret = True

while (fc < frameCount):
    ret, buf[fc] = cap.read()
    fc += 1

cap.release()
videoArray = buf

print (f"DURATION: {frameCount/videoFPS}")

您可以了解如何提取视频的特征，例如

frameCount

、

frameWidth

、

frameHeight

、

videoFPS

最后，持续时间应为帧数除以

videoFPS

变量。

所有帧都存储在

buf

内，因此如果您只想提取 1 帧，请迭代 buf 并仅提取 9 帧（每次迭代都会增加视频 FPS）。

Answer 3

这是我发现效果最好的代码。

import os
import cv2
import moviepy.editor

def getFrames(vid, output, rate=0.5, frameName='frame'):
    vidcap = cv2.VideoCapture(vid)
    clip = moviepy.editor.VideoFileClip(vid)

    seconds = clip.duration
    print('duration: ' + str(seconds))
    
    count = 0
    frame = 0
    
    if not os.path.isdir(output):
        os.mkdir(output)
    
    success = True
    while success:
        vidcap.set(cv2.CAP_PROP_POS_MSEC,frame*1000)      
        success,image = vidcap.read()

        ## Stop when last frame is identified
        print(frame)
        if frame > seconds or not success:
            break

        print('extracting frame ' + frameName + '-%d.png' % count)
        name = output + '/' + frameName + '-%d.png' % count # save frame as PNG file
        cv2.imwrite(name, image)
        frame += rate
        count += 1

rate

参数的值为

1/fps