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• OpenCV MP4 Creation

  7 mars 2017, par user5051092

  I’ve been trying to trying to write MP4 video files using OpenCV, in python.

  AVI creation works fine, both on linux and windows, when I use both :

  out = cv2.VideoWriter('x.avi', 0, 30, (640, 480))

  and

  fourcc = cv2.VideoWriter_fourcc(*"XVID")
  
  out = cv2.VideoWriter('x.avi', fourcc, 30, (640, 480))

  and even

  fourcc = cv2.VideoWriter_fourcc(*"XVID")
  
  out = cv2.VideoWriter('x', fourcc, 30, (640, 480))

  .

  When I try to save an MP4 however nothing ever saves - using :

  fourcc = cv2.VideoWriter_fourcc(*"H264")
  
  out = cv2.VideoWriter('x.mp4', fourcc, 30, (640, 480))

  and

  fourcc = cv2.VideoWriter_fourcc(*"AVC1")
  
  out = cv2.VideoWriter('x.mp4', fourcc, 30, (640, 480))

  No errors occur, just nothing saves.

  I’ve tried everything over the past few days, doing everything to avoid creating the AVI and then converting it to MP4 using ffmpeg as I find that to be horrible practice.

• iOS ffmpeg how to run a command to trim remote url video ?

  25 juillet 2016, par Pranoy C

  I was initially using the AVFoundation libraries to trim video but it has a limitation that it can’t do it for remote URLs and only works for local URLs.

  So after further research I found ffmpeg library which can be included in a Xcode project for iOS.
  I have tested the following commands to trim a remote video on command line :

  ffmpeg -y -ss 00:00:01.000 -i "http://i.imgur.com/gQghRNd.mp4" -t 00:00:02.000 -async 1 cut.mp4

  which will trim the .mp4 from 1 second to 3 second mark. This works perfectly via command line on my mac.

  I have been successfully able to compile and include ffmpeg library into a xcode project but not sure how to proceed further.

  Now I am trying to figure out how to run this command on an iOS app using the ffmpeg libraries. How can I do this ?

  If you can point me to some helpful direction, I would really appreciate it ! If I can get it resolved using your solution, I will award a bounty (in 2 days when it gives me the option).

• Webcam with FFmpeg on Mac : Selected framerate (29.970030) is not supported by the device

  24 juillet 2016, par Galaxy

  There was a very strange problem on Mac when I tried to access the webcam using FFmpeg.
  For example :

  ffmpeg -f avfoundation -i "1" -framerate 60 -vcodec libx264 -preset veryfast -f flv rtmp://localhost:1935/hls/test 

  No matter what framerate I set, the error was always the same.

  [avfoundation @ 0x7ff831800000] Selected framerate (29.970030) is not supported by the device
  
  [avfoundation @ 0x7ff831800000] Supported modes:
  
  [avfoundation @ 0x7ff831800000]   320x240@[120.101366 120.101366]fps
  
  [avfoundation @ 0x7ff831800000]   640x480@[120.101366 120.101366]fps
  
  [avfoundation @ 0x7ff831800000]   800x600@[60.000240 60.000240]fps
  
  [avfoundation @ 0x7ff831800000]   1024x768@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7ff831800000]   1280x720@[60.000240 60.000240]fps
  
  [avfoundation @ 0x7ff831800000]   1280x1024@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7ff831800000]   1920x1080@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7ff831800000]   320x240@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7ff831800000]   640x480@[30.000030 30.000030]fps
  
  [avfoundation @ 0x7ff831800000]   800x600@[20.000000 20.000000]fps
  
  [avfoundation @ 0x7ff831800000]   1024x768@[6.000002 6.000002]fps
  
  1: Input/output error

  I’ve searched for this problem for many days but still can’t find any solution. I’m very confused now.

  I hope someone using Mac could try the similar command to access the webcam in order to see if this is a common problem.