如何从 mp4 视频文件夹中提取帧并将它们传输到另一个文件夹？

Question

I have a folder full of mp4 clips (over 200). I want to take all those clips, extract their frames and send them to another folder to store all the frames in. This is what I have so far (part of the code) but it's only working when I have one mp4 file in the same folder:

import cv2     # for capturing videos
import math   # for mathematical operations
import matplotlib.pyplot as plt    # for plotting the images
import pandas as pd
from keras.preprocessing import image   # for preprocessing the images
import numpy as np    # for mathematical operations
from keras.utils import np_utils
from skimage.transform import resize   # for resizing images


count = 0
videoFile = "sample_vid.mp4"
cap = cv2.VideoCapture(videoFile)   # capturing the video from the given path
frameRate = cap.get(5) #frame rate
x=1
while(cap.isOpened()):
    frameId = cap.get(1) #current frame number
    ret, frame = cap.read()
    if (ret != True):
        break
    if (frameId % math.floor(frameRate) == 0):
        filename ="frame%d.jpg" % count;count+=1
        cv2.imwrite(filename, frame)
cap.release()
print ("Done!")

Again, i'm having some trouble dealing with the file directories in python and looping it so that it goes through all the files in another folder and send the frames extracted into another folder.

Answer 1

Use glob lib to find all mp4 files in your folder. Then run video2frames method against all videos.

import cv2
import math
import glob

def video2frames(video_file_path):
    count = 0
    cap = cv2.VideoCapture(video_file_path)
    frame_rate = cap.get(5)
    while cap.isOpened():
        frame_id = cap.get(1)
        ret, frame = cap.read()
        if not ret:
            break
        if frame_id % math.floor(frame_rate) == 0:
            filename = '{}_frame_{}.jpg'.format(video_file_path, count)
            count += 1
            cv2.imwrite(filename, frame)
    cap.release()

videos = glob.glob('/home/adam/*.mp4')
for i, video in enumerate(videos):
    print('{}/{} - {}'.format(i+1, len(videos), video))
    video2frames(video)

Tested on two videos. Here is what I've got:

Answer 2

You can use os.walk to fetch all mp4 names and iterate over them. There are other ways detailed in Find all files in a directory with extension .txt in Python (replace txt with mp4).

Create some files to find:

import os

with open("tata.mp4","w") as f: f.write(" ")
with open("tata1.mp4","w") as f: f.write(" ")
with open("tata2.mp4","w") as f: f.write(" ")

os.makedirs("./1/2/3")
with open("./1/subtata.mp4","w") as f: f.write(" ")
with open("./1/2/subtata1.mp4","w") as f: f.write(" ")
with open("./1/2/3/subtata2.mp4","w") as f: f.write(" ")

Find files:

startdir = "./"
all_files = []
for root,dirs,files in os.walk(startdir):
    for file in files:
        if file.endswith(".mp4"):
            all_files.append(os.path.join(root,file))

print(all_files) 

for f in all_files:
    # do your thing

Output:

['./tata2.mp4', './tata1.mp4', './tata.mp4', 
 './1/subtata.mp4', 
 './1/2/subtata1.mp4', 
 './1/2/3/subtata2.mp4']