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• Creating a video from data of server-side script

  8 mars 2016, par Peter Leupold

  My plan is to display the data that a server-side script generates in a video displayable on my web page. So far my approach is the following :

  1. A three dimensional integer array in a C script is use to accumulate the image data. Dimensions are width, breadth and color (R, G and B).
  2. The array is written to a ppm-file.
  3. The next picture is accumulated and written and so on.
  4. With ffmpeg a script merges the ppm-files to a mp4-video.

  Basically this works, but of course faster would be nicer. I would appreciate proposals for fundamentally different approaches as well as help on the following details :

  • Is there a file format simple as ppm that uses the HEX code for colors instead of triplets ? This would reduce the size of my array as well a the number of write operations.
  • Do I loose much time if I print every single value to the file with an fprintf operation instead of accumulating lines into a string ? Or do compilers optimize this kind of sequences of writes ?

• How to apply filter to video using ffmpeg c program android ndk

  13 juillet 2016, par Rajkumar

  I am newbie to ffmpeg with android. I have an input video birds.mp4 that have following settings

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'birds.mp4':
  
    Metadata:
  
      major_brand     : isom
  
      minor_version   : 512
  
      compatible_brands: isomiso2avc1mp41
  
      encoder         : Lavf54.59.106
  
    Duration: 00:00:21.60, start: 0.000000, bitrate: 574 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 320x176 [
  
  SAR 44:45 DAR 16:9], 440 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
  
      Metadata:
  
        handler_name    : VideoHandler
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, flt
  
  p, 127 kb/s (default)
  
      Metadata:
  
        handler_name    : SoundHandler

  I have compiled ffmpeg with libx264 as *.so file for android. And i write a Jni wrapper. Now I want to apply a filter to that input video and save it to output.mp4 with same setting as shown. I know basic terminologies encoding, decoding, muxing, transcoding.
  I want to know How to do this task ? and What are the techniques involved to do this task ?

  I use ffmpeg-3.1 c-source code grabbed from github and x264 from videolan site. i refer this sample it doesn’t guide me.

  If anybody experienced this problem please guide me right direction.

• Can't write video from MTS input with OpenCV

  26 juillet 2014, par Jack Simpson

  I’ve written a program with OpenCV where I input a video, apply some processing to each frame, and then write each frame to an output file. The code I’ve written has worked perfectly with lots of video types such as mp4, but when I try to use an MTS video as the format, the program will run correctly, and "imshow" will let me see the video as its running, but the output video is corrupted and I cannot open it like I usually can.

  I can upload more code if you like, but these are the main video writing areas of my code.

  VideoWriter output_cap("output.avi", 
  
  cap.get(CV_CAP_PROP_FOURCC),
  
  cap.get(CV_CAP_PROP_FPS),
  
  Size(cap.get(CV_CAP_PROP_FRAME_WIDTH),
  
  cap.get(CV_CAP_PROP_FRAME_HEIGHT)),true);
  
  
  
  // then I have a loop where I access each frame:
  
  
  
  imshow("video",frame);
  
  output_cap.write(frame);
  
  
  
  output_cap.write(frame);