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• HEVC video cutting issues using FFmpeg

  4 novembre 2017, par Dmitry Katkevich

  I need to cut videos using FFmpeg and I cannot transcode original videos (because of the performance reason). And I ran into a problem with HEVC videos from IPhone : there are glithes in the beginning of the cutted video.

  Here is how we converted videos before issue :

  ffmpeg.exe -i original.MOV -c:v copy -c:a aac -ss 4 -y good.mp4

  But for HEVC video there are glitches for 1 second in the beginning of the cutted video :

  

  Then I’ve tried to put seek option before input video :

  ffmpeg.exe -ss 4 -i original.MOV -c:v copy -c:a aac -y good.mp4

  The result seems good :

  

  After some googling it turns out that -ss option before input is faster but less accurate whereas -ss option after input and before output is slower but more accurate.

  So my questions are :

  • Why -ss option behaves differently then it is put before/after input ?

  • Is there a way to avoid glitches using output seek ffmpeg option ?

  • What does ’more/less accurate’ mean ? Does it mean that the seek may be too big or to little (bigger/less than we specified) ? How big may be this difference ?

• 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.

• How To Concatenate Two MP4 Videos With Different Aspect Ratios and Resolutions

  11 novembre 2017, par PortableDiag

  I am using ffmpeg to concatenate multiple MP4 videos, two at a time. The problem I am having is that the videos are often different resolutions and aspect ratios. One might come from a 480p webcam with a 1:1 aspect ratio and the other a brand new iPhone with 4k video and rectangular aspect ratio. Currently I must choose and set the aspect ratio manually and this results in one of the two videos becoming distorted, depending on the selected aspect ratio.

  How can I merge two videos so that the overall viewing field has a square aspect ratio but videos with a rectangular aspect ratio will be scaled to fit inside.

  I am using this command to merge the videos :

  ffmpeg -threads 1 -i '/518.mp4' -i '/516.mp4' -y -filter_complex "[0:v]scale=1080x1920,setpts=PTS-STARTPTS,setdar=0/1[v0];[1:v]scale=1080x1920,setpts=PTS-STARTPTS,setdar=0/1[v1];[v0][0:a][v1][1:a]concat=n=2:v=1:a=1" '/partial1.mp4'

  This is the result : https://www.dropbox.com/s/x1un7z1ljwr6tty/merged_newsort.mp4?dl=0

  Is it possible to apply a border to the rectangular video to give them a square aspect ratio ?

  How can I keep prevent distortion from occurring during the merge process ?

  Thanks in advance.