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• Video width is different in different devices

  8 novembre 2017, par David

  I have a special video when i want to get this video’s width code returns different value for Samsung galaxy s6 and Samsung note 3. I tested many different codes and libraries, but result is the same.
  in Samsung galaxy s6 : 640x480
  in Samsung note 3 : 853x480
  when I open this video with Gspot program it shows :

  Recommended Display Size : 853x480

  and this is the same value is returned by our IOS app tested in Iphone 7. aspect radio is not the same and this is big problem.

  here is some of codes I tested :

  (1)

      MediaMetadataRetriever metaRetriever = new MediaMetadataRetriever();
  
      metaRetriever.setDataSource(path);
  
      Bitmap bmp = metaRetriever.getFrameAtTime(-1);
  
  
  
      int height = bmp.getHeight();
  
      int width = bmp.getWidth();

  (2)

      MediaPlayer myMediaPlayer= MediaPlayer.create(ApplicationLoader.applicationContext, 
  
                                       Uri.fromFile(new File(path)));
  
  
  
      width = myMediaPlayer.getVideoWidth();
  
      height = myMediaPlayer.getVideoHeight();

  (3)

   MediaMetadataRetriever metaRetriever = new MediaMetadataRetriever();
  
          metaRetriever.setDataSource(path);
  
   String heights = metaRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_VIDEO_HEIGHT);
  
          String widths = metaRetriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_VIDEO_WIDTH);
  
      int height = Integer.valueOf(heights);
  
          int width = Integer.valueOf(widths);

  (4)

    MediaPlayer myMediaPlayer= MediaPlayer.create(ApplicationLoader.applicationContext, Uri.fromFile(new File(path)));
  
              myMediaPlayer.setOnVideoSizeChangedListener((mp, width, height) -> {
  
          int videoWidth = width;
  
          int videoHeight = height;
  
      );
  
              myMediaPlayer.setDataSource(path);
  
              myMediaPlayer.prepare();

  FFmpegMediaMetadataRetriever, FFmpeg Java, ExoPlayer and some other libraries returns the same result.

• avcodec/dovi_rpudec : fix reading el_bit_depth_minus8

  24 juin 2024, par Cosmin Stejerean

  avcodec/dovi_rpudec : fix reading el_bit_depth_minus8
  now that we are reading ext_mapping_idc as the upper 8 bits of
  
  el_bit_depth_minus8 we need to use get_ue_golomb_long rather than
  
  get_ue_golomb_31 for reading it
  

  • [DH] libavcodec/dovi_rpudec.c

• How can I programmatically write and read random video watermarks ?

  13 novembre 2017, par GreenTriangle

  I spent a few minutes trying to think of a clearer way to word my title, but I couldn’t manage it, sorry.

  I want to essentially canary trap video files : I am (hypothetically, this is not real but a personal exercise) offering them up to 5,000 different people, and if one gets leaked, I want to know who leaked it. Metadata is too easily emoved, so what I’d like to do is add a random and subtle watermark to each file, and store information about that in a database.

  For example : on Joe Smith’s copy, a 10x10 pixel 80% transparent red square in the upper left corner for 5 frames. On Diane Brown’s copy, a full-width 5-pixel 90% transparent black bar on the bottom edge for 15 frames. Then, if I find a leaked copy, I could check it against the database.

  I know this still isn’t foolproof : cropping would break co-ordinates, hue/brightness transforms would break colour reading, cutting time would break timestamps. But if I did want to do this anyway, what would be a good strategy for it ?

  My idea was to generate PNG overlays randomly, split the video into parts with mkvtoolnix/ffmpeg, re-encode the middle part with ffmpeg + overlay filter, and then rejoin them. But is this silly when there’s a "proper" way to do it ? And what would I be doing to read the watermarks, which I can’t even really conceive of ?