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• extracting single frame from MediaElemet or FFmpegInterop

  13 janvier 2016, par Jakub Wisniewski

  I am writing app (Windows Phone 8.1 Store App) that allows user to connect to IP Camera. I am using FFmpeg Interop library for ffmpeg which allows me to play eg. rtsp streams in media element. I need now a way to somehow extract a single frame from stream or from media element.

  I have tested other application wchih allows connecting to IP cameras - IP Centcom, and they have working snapshots only for mjpeg streams as far as I now (they were not working for rtsp). Becouse of that I belive that it is impossible or at very least very hard to export frame from media element.

  I have different question - if anyone has ever used FFmpeg Interop and would like to help/explain me how could I modify/extend FFmpegInteropMSS to add method called ’GetThumbnailForStream’ that would work similary to ’GetMediaStreamSource’ but would return single frame (bitmap or jpg) instead of MediaStreamSource ?

  Every help would be appreciated

  EDIT :

  I have found something ;

  in MediaSampleProvider in method WriteAVPacketToStream (line 123) there is line

  auto aBuffer = ref new Platform::Array(avPacket->data, avPacket->size);

  and I belive that this is the place that stores single frame data that is needed to convert into bitmap - now since I do not know c++ too much I have a question : how can I convert it into a form that I could return via public method ?

  When returning :

  Platform::Array^

  I get

  ’FFmpegInterop::MediaSampleProvider’ : a non-value type cannot have any public data members

  EDIT2 :

  Ok I am doing approprate projection to byte according to this microsoft information, now I need to check if this is correct data.

• Pulseaudio record multiple xfbv screens with python

  10 octobre 2020, par Eric Lagarda

  I’m trying to do something complicated and I need some help.

  


  I’m able to record a session (video and audio) with python using xvfb and ffmpeg.

  


  I just want to visit a page using selenium and record the video and audio. It’s working but when I try to run multiple instances, the audio is mixing between records.

  


  How can achieve that ? I’m using pulseaudio. I know that with alsa you can set like a interface per instance, but I don’t know how to do it.

  


  Thanks for you support and comments.

  


• Custom video cropping using ffmpeg

  5 octobre 2019, par Priyanka

  I’m using the writingminds ffmpeg library for cropping the video and getting the height, width ,x and y coordinates via a custom selector.
  I’m using the following code for cropping :

   String[] cmd = {"-i", path, "-filter:v", "crop=" + valuewidth + ":" + 
  
   valueheight + ":" + valuex + ":" + valuey, "-c:a", "copy", videoPath};
  
   execFFmpegBinary(cmd);

  On debugging, I’m getting this log :

  03-29 11:15:36.069 198-9920/? I/OMXCodec: [OMX.qcom.video.decoder.avc] Crop 
  
  rect is 368 x 272 @ (0, 0)
  
  03-29 11:15:36.209 198-684/? E/MediaPlayerService: WFD client is not created 
  
  03-29 11:15:36.229 198-9925/? I/OMXCodec: [OMX.qcom.video.decoder.avc] Crop 
  
  rect is 368 x 272 @ (0, 0)
  
  03-29 11:15:36.359 15596-15596/zoptal.com.appegovidexample 
  
  D/CropperActivity: ffmpeg : correct Loaded
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 
  
  '/storage/emulated/0/WhatsApp/Media/WhatsApp Animated Gifs/VID-20170318- 
  
  WA0000.mp4':
  
  
  
  Metadata:
  
  
  
  major_brand     : mp42
  
  
  
  minor_version   : 1
  
  
  
  compatible_brands: mp41mp42isom
  
  
  
  creation_time   : 2017-03-10 14:32:13
  
  
  
  Duration: 00:00:05.00, start: 0.080000, bitrate: 206 kb/s
  
  
  
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv,  
  
    /smpte170m/bt709), 368x272, 203 kb/s, 14 fps, 100 tbr, 600 tbn, 1200 tbc 
  
    (default)
  
  
  
    Metadata:
  
  
  
   creation_time   : 2017-03-10 14:32:13
  
  
  
   handler_name    : Core Media Video
  
  
  
   [Parsed_crop_0 @ 0x41e47550] Invalid too big or non positive size for width 
  
   '630' or height '592'
  
  
  
   [Parsed_crop_0 @ 0x41e47550] Failed to configure input pad on Parsed_crop_0
  
  
  
   Error opening filters!
  
   03-29 11:17:32.253 15596-15596/zoptal.com.appegovidexample 
  
    D/CropperActivity: Finished command : ffmpeg [Ljava.lang.String;@427f0d48
  
    03-29 11:17:32.273 15596-15596/zoptal.com.appegovidexample E/MediaPlayer: 
  
    Unable to create media player

  EDIT :
  I tried scaling the video by adding"scale=1280:720" to the command(as default crop rect based on video was 368 x 272 @ (0, 0)).Now, I’m getting this error :

   Metadata:
  
  
  
   creation_time   : 2017-03-10 14:32:13
  
  
  
   handler_name    : Core Media Video
  
  
  
   [NULL @ 0x41b65c80] Unable to find a suitable output format for 
  
   'crop=692:745:115:115'
  
  
  
   crop=692:745:115:115: Invalid argument

  EDIT : I solved it in the following way :

          float[]ghi=  cropImageView.getCropPoints();
  
          int a= Math.round(ghi[0]);
  
          int b= Math.round(ghi[1]);
  
          int c= Math.round(ghi[2]);
  
          int d= Math.round(ghi[3]);
  
          String[] cmde = {"-i", path ,"-filter:v", "crop=" + 240 + ":" + 
  
          220 + ":" + a + ":" + b, "-c:a", "copy", videoPath};
  
          execFFmpegBinary(cmde);