OpenCV视频未保存

Question

我正在尝试在OpenCV中保存视频，但我一直收到错误"could not demultiplex stream"。然后我检查了尺寸，发现它在kB。我主要想保存灰度视频，我该如何才能实现？

我需要使用特定的codec吗？

mplayer gives the following output

MPlayer 1.1-4.8 (C) 2000-2012 MPlayer Team
mplayer: could not connect to socket
mplayer: No such file or directory
Failed to open LIRC support. You will not be able to use your remote control.

Playing output.avi.
libavformat version 54.20.4 (external)
Mismatching header version 54.20.3
AVI file format detected.
[aviheader] Video stream found, -vid 0
AVI: Missing video stream!? Contact the author, it may be a bug :(
libavformat file format detected.
[lavf] stream 0: video (mpeg4), -vid 0
VIDEO:  [MP4V]  1280x720  24bpp   -nan fps    0.0 kbps ( 0.0 kbyte/s)
Clip info:
 encoder: Lavf54.20.4
Load subtitles in ./
Failed to open VDPAU backend libvdpau_nouveau.so: cannot open shared object file: No such file or directory
[vdpau] Error when calling vdp_device_create_x11: 1
==========================================================================
Opening video decoder: [ffmpeg] FFmpeg's libavcodec codec family
libavcodec version 54.35.1 (external)
Mismatching header version 54.35.0
Unsupported AVPixelFormat 53
Selected video codec: [ffodivx] vfm: ffmpeg (FFmpeg MPEG-4)
==========================================================================
Audio: no sound
Starting playback...
V:   0.0   0/  0 ??% ??% ??,?% 0 0 


Exiting... (End of file)

现在我尝试使用多种编解码格式

import imutils
import cv2
import numpy as np

interval = 30
outfilename = 'output.avi'
threshold=100.
fps = 10

cap = cv2.VideoCapture("video.mp4")

ret, frame = cap.read()
height, width, nchannels = frame.shape

fourcc = cv2.cv.CV_FOURCC(*'DIVX')
out = cv2.VideoWriter( outfilename,fourcc, fps, (width,height))

ret, frame = cap.read()
frame = imutils.resize(frame, width=500)
frame = cv2.cvtColor(frame, cv2.COLOR_RGB2GRAY)

while(True):

  frame0 = frame

  ret, frame = cap.read()
  frame = imutils.resize(frame, width=500)
  frame = cv2.cvtColor(frame, cv2.COLOR_RGB2GRAY)

  if not ret:
    deletedcount +=1
    break

  if np.sum( np.absolute(frame-frame0) )/np.size(frame) > threshold:
    out.write(frame)
  else:
    print "Deleted"

  cv2.imshow('Feed - Press "q" to exit',frame)

  key = cv2.waitKey(interval) & 0xFF

  if key == ord('q'):
    print('received key q' )
    break

cap.release()
out.release()
print('Successfully completed')

Answer 1

import numpy as np
import cv2

cap = cv2.VideoCapture(0)


out = cv2.VideoWriter('output.avi',-1, 20.0, (640,480))

while(cap.isOpened()):
    ret, frame = cap.read()
    if ret:
        gray = cv2.cvtColor(src=frame, code=cv2.COLOR_BGR2GRAY)

        out.write(gray)

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

cap.release()
out.release()
cv2.destroyAllWindows()

试试这个 选择Intel iyuv编解码器。 out.avi是非工作文件 output.avi是新的工作文件。

Answer 2

如果未保存视频，则可能是其捕获尺寸（其硬编码为(640,480)）的原因。

您可以尝试以下代码：

cap = cv2.VideoCapture(0)

fourcc_codec = cv2.VideoWriter_fourcc(*'XVID')
fps = 20.0
capture_size = (int(cap.get(3)), int(cap.get(4)))

out = cv2.VideoWriter("output.avi", fourcc_codec, fps, capture_size)