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• FFMPEG - Overlaying video with transparency, alpha has strange threshold

  3 novembre 2016, par tanker_

  I’m attempting to overlay an Apple ProRes 4444 video with a alpha/transparency onto a normal video. However, upon inspecting the final output from FFMPEG, compared to the same files overlaid on top of one another and rendered in Final Cut Pro, there is a discrepancy in how they render the edges around the object.

  Screenshot comparison.

  Additional closeup.

  Here is my input :

  ffmpeg \
  
      -i background.MOV -x264opts colormatrix=bt709 \
  
      -i alpha_object.MOV -x264opts colormatrix=bt709 \
  
      -filter_complex " \
  
          [0:v]setpts=PTS-STARTPTS, scale=1920x1080[top]; \
  
          [1:v]setpts=PTS-STARTPTS, scale=1920x1080, \
  
               colorchannelmixer=aa=1.0[bottom]; \
  
          [top][bottom]overlay=shortest=1" \
  
      -vcodec libx264 -qp 15 -an -shortest output.MOV

  Any idea what could be wrong ? Is there a option within FFMPEG’s available filters that I’m missing ?

  All files are ingested and rendered in 1920x1080.

• FFMPEG - Overlaying video with transparency, alpha has strange threshold

  6 mars 2019, par tanker_

  I’m attempting to overlay an Apple ProRes 4444 video with a alpha/transparency onto a normal video. However, upon inspecting the final output from FFMPEG, compared to the same files overlaid on top of one another and rendered in Final Cut Pro, there is a discrepancy in how they render the edges around the object.

  Screenshot comparison :

  

  Additional closeup :

  

  Here is my input :

  ffmpeg \
  
      -i background.MOV -x264opts colormatrix=bt709 \
  
      -i alpha_object.MOV -x264opts colormatrix=bt709 \
  
      -filter_complex " \
  
          [0:v]setpts=PTS-STARTPTS, scale=1920x1080[top]; \
  
          [1:v]setpts=PTS-STARTPTS, scale=1920x1080, \
  
               colorchannelmixer=aa=1.0[bottom]; \
  
          [top][bottom]overlay=shortest=1" \
  
      -vcodec libx264 -qp 15 -an -shortest output.MOV

  Any idea what could be wrong ? Is there a option within FFMPEG’s available filters that I’m missing ?

  All files are ingested and rendered in 1920x1080.

• how to set ffmpeg bitrate, frame per second when scalling from low to high resolution/ high to low

  21 janvier 2015, par user2303069

  I’m developing a video sharing app for mobile device users. I noticed if I convert video with ffmpeg from a low(ex 240x320) to a higher resolution(ex 480x-1) the video looses quality and also there is no sound at the end. My question to you is how should I filter(how many fps,bitrate ect) the converted file ? In terms of parameters, how should I convert to make sure the video comes out in good quality at it’s destination(the user who will play it on their mobile device[Android/BlackBerry]).

  Here is my current code(java) :

  /************************  CONVERTING    TIME   *************************
  
                         method to convert video-clip
  
  */
  
  if(sn.toString().trim().startsWith("<>")){
  
      String info=sn.toString().trim().substring(2);
  
      String scale=info.substring(0, info.indexOf("."));
  
      String width=scale.substring(0, scale.indexOf("x"));
  
      String name=info.substring(info.indexOf(".")+1, info.length());
  
      String to = null;
  
      String from;
  
  
  
      try{
  
          //calculate to and from
  
          to=name.substring(0, name.indexOf("$"));
  
          from=name.substring(name.indexOf("$")+1, name.lastIndexOf("$"));
  
          gui.textArea1.append("\nStart converting...: to="+to+" from="+from+" fileName="+name);
  
      }catch(NullPointerException npe){
  
          gui.textArea1.append("\nNullpointer in calculate name in converting: "+npe.getMessage());
  
      }
  
  
  
      final Path videoIn = Paths.get("c:\\wamp\\www\\iclips\\videoMessages\\"+name);
  
      final Path encodingFile = Paths.get("c:\\wamp\\www\\iclips\\videoMessages\\scaled-"+name);
  
      final Path errorFile = Paths.get("c:\\ffmpeg\\bin\\error.txt");
  
      String pro;
  
      int w=Integer.parseInt(width);
  
  
  
      if(w<=240){
  
          pro="baseline";
  
      }else if(w>240&&w<=480){
  
          pro="main";
  
      }else if(w>480){
  
          pro="high";
  
      }else{
  
          pro="baseline";
  
      }
  
      //int retCode;
  
  
  
      try {
  
          Files.deleteIfExists(encodingFile);
  
          Files.deleteIfExists(errorFile);
  
  
  
          final ProcessBuilder pb 
  
              = new ProcessBuilder("c:\\ffmpeg\\bin\\ffmpeg.exe",
  
                  "-i", videoIn.toString(),
  
                  "-y", 
  
                  "-vf", "scale="+width+":-1", 
  
                  // "-pix_fmt","yuv420p",   
  
                  "-vcodec", "libx264",
  
                  "-vprofile", pro,    
  
                  "c:\\wamp\\www\\iclips\\videoMessages\\scaled-"+name
  
          ); //or other command....                    
  
  
  
          pb.redirectError(errorFile.toFile());
  
          pb.redirectOutput(encodingFile.toFile());
  
  
  
          final Process p = pb.start();
  
          try {
  
              p.waitFor();
  
              if(p.exitValue()==0){
  
                  gui.textArea1.append("\n+++++++++++++Vic-^clip converted successfully:"
  
                          + " ExitValue=["+String.valueOf(p.exitValue())+"] ++++++++++++++");
  
                  if(Files.deleteIfExists(videoIn)){
  
                      gui.textArea1.append("\n"+videoIn.toString()+" deleted!");
  
                  }
  
                  sendMsg("Scalling successfull:-)   Video-clip name=scaled-"+name+"_", "\nSent scaled successfull "+username);
  
                  NotifyClientOfScaledVideoMessage(to,"^scaled-"+name+"_");
  
              }else{
  
                  gui.textArea1.append("\nSomething went wrong with process-convert: ExitValue="+String.valueOf(p.exitValue()));
  
                  sendMsg("Unable to scale video, try again._", "\nSent scaled failed to "+username);
  
              }
  
          } catch (InterruptedException e) {
  
              gui.textArea1.append("\nInterrupted process convert: "+e.getMessage());
  
          }
  
      } catch (IOException e) {
  
          // deal with e here
  
          gui.textArea1.append("\nIOException in Convert Video: "+e.getMessage());
  
      }
  
  }

  Thank you very much.