Newest 'ffmpeg' Questions - Stack Overflow

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• Running cmd in python (ffmpeg)

  29 mars 2017, par Coolcrab

  Atm I have this as my code, the first line seems to work well but the 2nd gives errrors.

  os.chdir('C://Users/Alex/Dropbox/code stuff/test')
  subprocess.call(['ffmpeg', '-i', 'test%d0.png', 'output.avi'])
  

  error:

  Traceback (most recent call last):
    File "C:\Users\Alex\Dropbox\code stuff\solarsystem.py", line 56, in 
      subprocess.call(['ffmpeg', '-i', 'test%d0.png', 'output.avi'])
    File "C:\Python27\lib\subprocess.py", line 524, in call
      return Popen(*popenargs, **kwargs).wait()
    File "C:\Python27\lib\subprocess.py", line 711, in __init__
      errread, errwrite)
    File "C:\Python27\lib\subprocess.py", line 948, in _execute_child
      startupinfo)
  WindowsError: [Error 2] The system cannot find the file specified
  

• opencv rtsp stream protocol

  29 mars 2017, par k_kaz

  I want to process and display a network rtsp stream that is created from a raspberry camera. I have this code:

  #include 
  #include 
  #include highgui/highgui.hpp>
  #include imgproc/imgproc.hpp>
  
  int main(int argc, char** argv) {
  
      cv::VideoCapture * stream = new cv::VideoCapture("rtsp://192.168.55.151:8554/");
      if (!stream->isOpened()) return -1;
  
      cv::namedWindow("rtsp_stream", CV_WINDOW_AUTOSIZE);
      cv::Mat frame;
  
      while (true) {
  
          if (!stream->read(frame)) return -1;
  
          cv::imshow("rtsp_stream", frame);
          cv::waitKey(15);
      }
  
      return 1;
  }
  

  When the stream is not live, the execution of this results in:

  [tcp @ 0xa12480] Connection to tcp://192.168.55.151:8554?timeout=0 failed: Connection refused
  

  Which means that the stream tries to connect with tcp. When the stream is live, the execution results in:

   [rtsp @ 0xb07960] method SETUP failed: 461 Client error
  

  From internet research i found that the problem may be that the stream uses udp. If i change the URL to:

  "udp://192.168.55.151:8554/"
  

  Then the execution freezes in the cv::VideoCapture("udp://192.168.55.151:8554/");

  VLC is able to open the rtsp stream. As i am given to understand, ffmpeg is used to decode the stream with opencv. When i run:

  ffmpeg -rtsp_transport udp -i rtsp://192.168.55.151:8554/ -t 5 test.mp4
  

  the stream decoding and saving is successful. So how can i specify the lower level protocol to be udp in the opencv code? Is there another way to do it with opencv?

  EDIT: If i change the ffmpeg command to use tcp, i.e:

  ffmpeg -rtsp_transport tcp -i rtsp://192.168.55.151:8554/ -t 5 test.mp4
  

  then i get the same exact error with the c++ code, 461 client error

  EDIT: When the code uses the udp:// link, after some 15 seconds of freeze, the execution returns with error

• Video from set of images with fading

  29 mars 2017, par MarkusHH

  i need to generate a video (mp4) from a set of images in a folder. My command works fine but i want the frames to fade in/out, crossfade or something to make the vid "smoother".

  My command:

  exec("ffmpeg -framerate 30  -y -pattern_type glob -i 'images/*.jpg' -filter:v scale=1280:-1 -q:v 0 -vcodec mpeg4 -strict -2 -movflags faststart folder/video.mp4 2> ffmpeg_log.txt");
  

  Thanks for any assistance

• ffmpeg - extract exact number of frames from video

  29 mars 2017, par Michael B

  I want to create a maximum of 30 images from a video (and tile them for a sprite sheet).

  I've tried using the 'select' with 'mod' but if the total number of frames does not fit neatly into the desired number of images (30) then I sometimes end up with more images, sometimes less.

  For example if my video is 72 frames long, my 'mod' would be 72 / 30, which is 2.4.

  I'm running this from a python script so i'm doing something like the following for the filter:

  select='not(mod(n\," + str(mod) + "))'
  

  I think the mod has to be an integer (?) so I could either round down and use 2 which gives me 36 images or round up which gives me 24 images

  Whats the best way to get exactly 30? - obviously the interval wouldn't be identical but thats fine.

  Maybe I could use a for loop to generate a list of the frames closest to the desired interval and then pass that in as the select filter?

  e.g. to get the frames I would do something like this:

  nframes = 72 # number of frames in video
  outImages = 30 # number of images I want
  mod = float(nframes) / outImages # 2.4
  
  frames = []
  
  idx = 1
  
  while i < nframes:
      print str(idx) + ": " + str(math.floor(i+0.5)) 
      frames.append(int(math.floor(i+0.5)))
      idx += 1
      i += mod
  

  Then am I able to pass that (the frames list) into the ffmpeg command? Or can I tell ffmpeg to do something similar?

• ffmpeg- blend transition between images specified in a text file

  29 mars 2017, par hack

  how can i create a blend transition effect between specified images? I have the file paths to images in a text file. My requirement is that i should be able to do a blend transition between specific images (whose path are in text file) for a specific duration. I also have to annotate these images with text.For that i am using drawtext filter. The blend transition should be between annotated images.

  Thanks