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• Layer black & white video over background so black pixels are transparent in FFMPEG

  4 février 2018, par Dan Weaver

  I’m trying to blend a video containing black and white animated text over a static background image. I can successfully blend them but no matter what blend mode I use I can’t get the effect I want.

  I’m looking for an effect similar to Photoshop’s ’Add’ blend mode where the color values of each pixel are added together. This results in no change where the top layer (video) has black pixels, effectively making the black background appear transparent.

  This is what I’m trying to achieve :
  

  ffmpeg -i text.mp4 -loop 1 -i image.jpg \
-filter_complex 'blend=all_mode=addition' -t 1 result.mp4

  I tried all the modes of the blend filter but none of them produce this effect. I thought Addition would be the one to work but the resulting video has a pink tint. Maybe there is some mismatch between color channels ?

  How can I get the result I’m looking for ?

• FFMPEG command fails for file path with white spaces

  7 février 2018, par user3904345

  I am executing the below ffmpeg command for trimming videos.The issue I am having is that if filepath contains spaces then the command fails.I tried many ways to handle spaces but none of them worked except moving file to a path that doesn’t have space and then executing the command with new file path as source.
  Below is the command-

   execFFmpegBinary("-i " +  filepath   + " -ss " + startMs / 1000 + " -to " + endMs / 1000 + " -strict -2 -async 1 " + dest.getAbsolutePath());
  
  
  
  
  
  
  
  private void execFFmpegBinary(final String command) {
  
          try {
  
              ffmpeg.execute(command, new ExecuteBinaryResponseHandler() {
  
                  @Override
  
                  public void onFailure(String s) {
  
                      Log.e("Previewragment", "FAILED with output : " + s);
  
                  }
  
  
  
                  @Override
  
                  public void onSuccess(String s) {
  
                      Log.e("Previewragment", "SUCCESS with output : " + s);
  
                  }
  
  
  
                  @Override
  
                  public void onProgress(String s) {
  
                      Log.e("Previewragment", "Started command : ffmpeg " + command);
  
                      Log.e("Previewragment", "progress : " + s);
  
                  }
  
  
  
                  @Override
  
                  public void onStart() {
  
                      Log.e("Previewragment", "Started command : ffmpeg " + command);
  
  
  
                  }
  
  
  
                  @Override
  
                  public void onFinish() {
  
  
  
  
  
  
  
                  }
  
              });
  
          } catch (FFmpegCommandAlreadyRunningException e) {
  
              // do nothing for now
  
          }
  
      }

  I saw this answer and tried

   String addQuotes(String in ) {
  
          return "\"" + in + "\"";
  
      }
  
  execFFmpegBinary("-i " +  addQuotes(filepath)   + " -ss " + startMs / 1000 + " -to " + endMs / 1000 + " -strict -2 -async 1 " + dest.getAbsolutePath())

   ;

• FFmpeg : How to color-key all colors except blue and white ?

  21 février 2018, par DanielNg

  I know how to colorkey a specific color from an overlay video based on the documentation from FFmpeg. Here is the code I used to colorkey the black color out of a video then overlay it with a base video keeping the audio from the overlaid video :

  "ffmpeg -i " + baseVid + " -i " + overlayVid + " -y" + ' -filter_complex "[1:v]colorkey=0x000000:0.6:0.0[ckout];[0:v][ckout]overlay=shortest=1[out]" -shortest -map 1:a -map "[out]" ' + output

  However, my problem is that the overlaid video also contains other colors such as blue, white, brown, grey, green. Even though they are only small portions compared to the black that has been removed, they make the colorkeyed overlaid video look really dirty. I want to keep only the two main colors (blue and white) and removing the rest from the overlaid video. How do I do this using FFmpeg. I tried this code but it did not work.