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• ffmpeg Get time of frames from trimmed video

  17 novembre 2017, par TheOtherguyz4kj

  I am using FFmpeg in my application to extract frames from a video, the frames will be added to a trim video view where you get an illustration as to what is happening in the video at a specific time within the video. So each frame needs to represent some time within the video.

  I dont quite understand how FFmpeg is producing the frames. Here is my code :

  "-i",
  
  videoCroppedFile.getAbsolutePath(),
  
  "-vf",
  
  "fps=1/" + frameSeperation,
  
  mediaStorageDir.getAbsolutePath() +
  
  "/%d.jpg"

  My app allows you to record a video at a max length of 20s. The number of frames extracted from the video depnds on how long the captured video is. frameSeperation is calculated doing the below code.

  String time = retriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
  
      long videoLength = Long.parseLong(time) / 1000;
  
      double frameSeperationDouble = (double) videoLength;
  
      // Divide by 11 because there is a maximum of 11 frames on trim video view
  
      frameSeperationDouble /= 11;
  
      frameSeperationDouble = Math.ceil(frameSeperationDouble);
  
      int frameSeperation = (int) frameSeperationDouble;

  Maybe the above logic is very bad, if there is a better way please can somebody tell me.

  Anyway I run the code and below are a few test cases :

  • A video captured with a length of 6 seconds has 7 frames.
  • A video captured with a length of 2 seconds has 3 frames.
  • A video captured with a length of 10 seconds has 12 frames.
  • A video captured with a length of 15 seconds has 9 frames.
  • A video captured with a length of 20 seconds has 11 frames.

  There is no consistency, and I find it hard to put timestamps against each frame because of this. I feel like my logic is wrong or im not understanding. Any help is much appreciated

  Update 1

  So I did what you said in comments :

   final FFmpeg ffmpeg = FFmpeg.getInstance(mContext);
  
          final File mediaStorageDir = new File(Environment.getExternalStorageDirectory()
  
                  + "/Android/data/"
  
                  + mContext.getPackageName()
  
                  + "/vFrames");
  
  
  
      if (!mediaStorageDir.exists()){
  
          mediaStorageDir.mkdirs();
  
      }
  
  
  
      MediaMetadataRetriever retriever = new MediaMetadataRetriever();
  
      retriever.setDataSource(mContext, Uri.fromFile(videoCroppedFile));
  
      String time = retriever.extractMetadata(MediaMetadataRetriever.METADATA_KEY_DURATION);
  
      long videoLength = Long.parseLong(time) / 1000;
  
      double frameSeperationDouble = (double) videoLength / 8;
  
  
  
      retriever.release();
  
  
  
      final String cmd[] = {
  
  
  
              "-i",
  
              videoCroppedFile.getAbsolutePath(),
  
              "-vf",
  
              "fps=1/" + frameSeperationDouble,
  
              "-vframes," + 8,
  
              mediaStorageDir.getAbsolutePath() +
  
              "/%d.jpg"
  
      };

  I also tried "-vframes=" + 8 at the same point where I put vFrames in cmd. It doesnt seem to work at all now no frames are being extracted from the video

• Anomalie #4430 : image_reduire gère mal les arrondis

  4 février 2020, par jluc -

  L’image initiale fait 640 × 427 pixels.
  |image_proportions1,1,focus produit correctement une image de 427x427. Il est donc probable qu’on reproduit le pb directement à partir d’une image de 427x427

  En tout cas le résultat final fait réellement 200x201.

• Optimize ffmpeg overlay and loop filters

  5 novembre 2020, par Miro Barsocchi

  I have a video, video.mp4, of 30 seconds, and I have an audio that can change in length, audio.mp3.

  


  My final idea is to have an output video of a loop of video.mp4 for the total length of the audio.mp3, and an overlay of the waveform of the audio.mp3. What I've done is this, in a bash script :

  


  # calculate length of the audio and of the video
tot=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 audio.mp3)
vid=$(ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 video.mp4)
# how many base video we need to loop into the waveform video?
repeattime=`echo "scale=0; ($tot+$vid-1)/$vid" | bc`

# ffmpeg final command
ffmpeg -stream_loop $repeattime -i video.mp4 -i audio.mp3 -filter_complex "[1:a]showwaves=s=1280x100:colors=Red:mode=cline:rate=25:scale=sqrt[outputwave]; [0:v][outputwave] overlay=0:main_h-overlay_h [out]" -map '[out]' -map '1:a' -c:a copy -y output.mp4


  


  Is there a better way to do it in a single ffmpeg command ? I know it exists the loop filter in ffmpeg, but it loops frames and I don't know the number of frames of the video.mp4. Also, using $repeattime can result in a number of loop longer then needed (because math calculation is done round up)