24

我正在尝试从 OSX 下的 OpenCV 的 python 包装器创建一个视频。我正在使用 python 2.7.1、opencv 2.3.1a 和来自 willowgarage 的 python 包装器，这些包装器随该版本的 opencv 一起提供。我有：

import cv,cv2
w = cv2.VideoWriter('foo.avi', cv.FOURCC('M','J','P','G'), 25, (100,100))
for i in range(100):
    w.write(np.ones((100,100,3), np.uint8))

OpenCV 说

WARNING: Could not create empty movie file container.
Didn't successfully update movie file.
... [ 100 repetitions]

我不确定接下来要尝试什么

4

10 回答 10

53

关于这个主题有很多过时和不正确的在线指南——我想我几乎每一个都试过了。在查看了 Mac OSX 上基于 QTKit 的 VideoWriter 源代码实现之后，我终于能够使用以下代码让 VideoWriter 输出有效的视频文件：

fps = 15
capSize = (1028,720) # this is the size of my source video
fourcc = cv2.cv.CV_FOURCC('m', 'p', '4', 'v') # note the lower case
self.vout = cv2.VideoWriter()
success = self.vout.open('output.mov',fourcc,fps,capSize,True)

要写入一个图像帧（注意 imgFrame 必须与上面的 capSize 大小相同，否则更新将失败）：

self.vout.write(imgFrame)

完成后请务必：

vout.release() 
self.vout = None

这适用于 Mac OS X 10.8.5 (Mountain Lion)：不保证其他平台。我希望这个片段可以节省其他人几个小时的实验时间！

于 2013-10-06T18:27:29.060 回答
9

我使用的是 macOS High Sierra 10.13.4、Python 3.6.5、OpenCV 3.4.1。

下面的代码（来源：https ://www.learnopencv.com/read-write-and-display-a-video-using-opencv-cpp-python/ ）打开相机，按“q”成功关闭窗口, 并将视频保存为 .avi 格式。

请注意，您需要将其作为 .py 文件运行。如果在 Jupyter Notebook 中运行，窗口在关闭时会挂起，需要强制退出 Python 才能关闭窗口。

import cv2
import numpy as np
 
# Create a VideoCapture object
cap = cv2.VideoCapture(0)
 
# Check if camera opened successfully
if not cap.isOpened(): 
  print("Unable to read camera feed")
 
# Default resolutions of the frame are obtained.The default resolutions are system dependent.
# We convert the resolutions from float to integer.
frame_width = int(cap.get(3))
frame_height = int(cap.get(4))
 
# Define the codec and create VideoWriter object.The output is stored in 'outpy.avi' file.
out = cv2.VideoWriter('outpy.avi',cv2.VideoWriter_fourcc('M','J','P','G'), 10, (frame_width,frame_height))
 
while True:
  ret, frame = cap.read()
 
  if ret: 
     
    # Write the frame into the file 'output.avi'
    out.write(frame)
 
    # Display the resulting frame    
    cv2.imshow('frame',frame)
 
    # Press Q on keyboard to stop recording
    if cv2.waitKey(1) & 0xFF == ord('q'):
      break
 
  # Break the loop
  else:
    break 
 
# When everything done, release the video capture and video write objects
cap.release()
out.release()
 
# Closes all the frames
cv2.destroyAllWindows()
于 2018-06-23T02:40:22.540 回答
4

在尝试了各种选项后，我发现我使用的 frame.size 不适合 VideoWriter 中指定的大小：所以将其设置为 iMac 1280x720 的默认值就可以了！

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc('m', 'p', '4', 'v')
out = cv2.VideoWriter()
succes = out.open('output.mp4v',fourcc, 15.0, (1280,720),True)
while(cap.isOpened()):
    ret, frame = cap.read()
    if ret==True:
        frame = cv2.flip(frame,0)
        # write the flipped frame
        out.write(frame)
        cv2.imshow('frame',frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    else:
        break

# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
于 2014-11-10T11:20:22.220 回答
2

这是“大小”问题。

import cv2
import time

filename = time.strftime("%m-%d-%H-%M-%S") + '.avi'
fps = 16

cap = cv2.VideoCapture(0)

#in this way it always works, because your get the right "size"
size = (int(cap.get(cv2.cv.CV_CAP_PROP_FRAME_WIDTH)),
        int(cap.get(cv2.cv.CV_CAP_PROP_FRAME_HEIGHT)))
fourcc = cv2.cv.FOURCC('8', 'B', 'P', 'S')     #works, large
out = cv2.VideoWriter(filename, fourcc, fps, size, True)

#in this way, you must set the "size" to your size, 
#because you don't know the default "size" is right or not
#cap.set(3, 640)
#cap.set(4, 480)
#out = cv2.VideoWriter(filename, fourcc, fps, (640, 480), True)

while(cap.isOpened()):
    ret, frame = cap.read()
    if ret == True:
        out.write(frame)
        cv2.imshow('frame', frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break;

else:
    print 'Error...'
    break;

cap.release()
out.release()
cv2.destroyAllWindows()
于 2015-07-02T06:12:36.567 回答
2

这是一个适用的版本：

  • Python 3.6.3
  • OpenCV 3.3.1
  • macOS 10.13.1

安装了brew install opencv.

#!/usr/bin/env python3

import cv2

def main():
    vc = cv2.VideoCapture()
    if not vc.open('input.mp4'):
        print('failed to open video capture')
        return

    fourcc = cv2.VideoWriter_fourcc(*'mp4v')
    # Match source video features.
    fps = vc.get(cv2.CAP_PROP_FPS)
    size = (
        int(vc.get(cv2.CAP_PROP_FRAME_WIDTH)),
        int(vc.get(cv2.CAP_PROP_FRAME_HEIGHT)),
    )

    vw = cv2.VideoWriter()
    if not vw.open('output.mp4', fourcc, fps, size):
        print('failed to open video writer')
        return

    while True:
        ok, frame = vc.read()
        if not ok:
            break

        # Flip upside down.
        frame = cv2.flip(frame, 0)

        # Write processed frame.
        vw.write(frame)

        cv2.imshow('frame', frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break

    vc.release()
    vw.release()
    cv2.destroyAllWindows()

if __name__ == "__main__":
    main()
于 2017-12-03T06:06:03.343 回答
1

这是对我有用的@ToddStellanova 答案的变体：

def write_video(image_dir):
  '''
  Writes a video from a set of images in `image_dir`
  '''
  target = join('data/labelled-videos',
                basename(image_dir) + '.mp4v')
  codec = cv2.cv.CV_FOURCC('m', 'p', '4', 'v')
  size = (256, 256)
  v = cv2.VideoWriter(target, codec, 16, size)
  for image_name in listdir(image_dir):
    image_filename = join(image_dir, image_name)
    arr = np.asarray(Image.open(image_filename))
    assert arr.shape[:2] == size
    v.write(arr)
于 2014-10-14T17:24:26.093 回答
1

您的 ffmpeg 版本可能已过时。我在使用 ffmpeg 0.8 时遇到了类似的问题，升级到 ffmpeg 0.11 后它运行良好。

于 2012-10-23T22:36:24.787 回答
1

我的问题在于frame_width和frame_height。尝试以下操作：

import cv2

cap = cv2.VideoCapture(0)

# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'MJPG')
frame_width = int(cap.get(3))
frame_height = int(cap.get(4))
size = (frame_width, frame_height)
fps = 10
out = cv2.VideoWriter("output.avi", fourcc, fps, size)

while(cap.isOpened()):
    ret, frame = cap.read()

    if ret:
        out.write(frame)  # write the frame
        cv2.imshow('frame', frame)
    else:
        break
    if cv2.waitKey(1) == 27:  # Esc
        break

# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()
于 2020-02-08T22:46:14.020 回答
0

这不是个好主意

您必须创建一个VideoWriter结构并使用方法WriteFrame：

import cv
cv.NamedWindow('cap', 1)
w = cv.CreateVideoWriter('test.avi',cv.CV_FOURCC('X','V','I','D'),25,(640,480))
cap = cv.CaptureFromCAM(0)
while(1):
    img = cv.QueryFrame(cap)
    cv.ShowImage('cap', img)
    cv.WriteFrame(w, img)
    if cv.WaitKey(1) == 27:
        break
cv.DestroyWindow('cap')
于 2012-09-28T09:30:35.807 回答
0

感谢@TeddStellanova

这里是 XCode C++ 版本：

int fWidth = capture.get(CV_CAP_PROP_FRAME_WIDTH);
int fHeight = capture.get(CV_CAP_PROP_FRAME_HEIGHT);
string vid_path = path + "frames.mov";
VideoWriter vid(vid_path,CV_FOURCC('m','p','4','v'),30,Size(fWidth,fHeight),true);
于 2016-04-08T08:25:32.640 回答