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• FFMPEG decoding video produces discolored YUV frame

  13 mai 2019, par Jeff Gong

  I am using FFMPEG directly to decode a single video frame encoded in H.264 from a test video I’m running using the following command :

  ffmpeg -i test.mp4 -ss 00:00:00 -vframes 1 -pix_fmt yuv420 output.yuv

  For some reason, when I open the file on a YUV viewer, I can distinctly tell that the colors are slightly off compared to the original input. I’ve tried to play with the colorspace and color matrix options, but nothing I do seems to replicate exactly the original colors.

  For example, I’ve also tried the following commands :

  ffmpeg -i test.mp4 -ss 00:00:00 -vframes 1 -pix_fmt yuv420p -vf colormatrix=bt470:bt709 output.yuv

  and

  ffmpeg -i test.mp4 -ss 00:00:00 -vframes 1 -pix_fmt yuv420p -color_primaries bt709 -color_trc linear -colorspace bt709 output.yuv

• Android javacv FFMpeg overlay animated gif over video

  5 avril 2019, par Diego Perez

  I’m developing an Android app that creates a video (from an image plus an mp3 file) with javacv and FFMpeg and the video generation part is working fine, but my problem comes now that I would like to overlap a transparent background animated gif over the video, and I’m really stuck with it and I have no success on every attempt so far.

  To be honest it is being my first experience with javacv and FFMpeg, so I have little knowledge on how to work with filters.

  I’ll paste my complete video creation method below and let’s see if anyone can help me. Again, my problem is overlapping the animated gif, the video (removing the filter part) is being created just fine. The most I was able to achieve is overlapping a static (one frame) small gif (with no transparency) on the top left corner of video, but what I’d like to achieve is a transparent gif with the same dimensions of video over it.

  Maybe you will see nonsense code, but remember this is due to my lack of knowledge with javacv and FFMpeg filters.

  I hope anyone can help me.

  Thanks.

  PS. I have read this post : javaCV Android, Strange colors on overlay while streaming to rtmp server

  of @schw4ndi but I wasn’t able to do anything with it.

  static String recordVideo(JSONObject objJSON) {
  
  
  
      try {
  
          fileName = objJSON.has("file_name") ? String.valueOf(objJSON.getString("file_name")) : "";
  
          videoPath = objJSON.has("video_path") ? String.valueOf(objJSON.getString("video_path")) : "";
  
      } catch (JSONException e) {
  
          ExceptionHandler.logException(e);
  
      }
  
  
  
      String strReturn = Enum.Result.OK;
  
  
  
      if (!fileName.equals("") && !videoPath.equals("")) {
  
          try {
  
              String outputFilename = videoPath + "/" + fileName;
  
              //video grabber
  
              FrameGrabber grabber1 = new FFmpegFrameGrabber(outputFilename + ".jpg");
  
              //audio grabber
  
              FrameGrabber grabber2 = new FFmpegFrameGrabber(outputFilename + ".mp3");
  
  
  
              grabber1.start();
  
              grabber2.start();
  
  
  
              FFmpegFrameRecorder recorder = new FFmpegFrameRecorder(outputFilename + ".mp4", 1080, 1920,2);
  
  
  
              //video
  
              recorder.setVideoCodec(avcodec.AV_CODEC_ID_H264);
  
              recorder.setVideoOption("tune", "zerolatency");
  
              recorder.setFrameRate(30);
  
              recorder.setVideoBitrate(128000);
  
              recorder.setVideoOption("crf", "28");
  
              recorder.setVideoQuality(0); //highest quality
  
              recorder.setVideoOption("preset", "fast");
  
              recorder.setFormat("mp4");
  
  
  
              //audio
  
              recorder.setAudioCodec(avcodec.AV_CODEC_ID_AAC);
  
              recorder.setSampleRate(44100);
  
              recorder.setAudioBitrate(128000);
  
              recorder.setAudioOption("crf", "0"); //no variable bitrate audio (constant rate factor)
  
              recorder.setAudioQuality(0); //highest quality
  
  
  
              FFmpegFrameFilter filter = null;
  
              try{
  
                  filter = new FFmpegFrameFilter("movie=" + videoPath + "/anim01.gif [logo];[in][logo]overlay=0:0:format=yuv420 [out]",1080, 1920);
  
                  filter.start();
  
              }catch (FrameFilter.Exception e){
  
                  e.printStackTrace();
  
              }
  
  
  
              recorder.start();
  
  
  
              Frame frame1, frame2 = null, frame3 = null;
  
  
  
              while ((frame1 = grabber1.grabFrame()) != null ||
  
                      (frame2 = grabber2.grabFrame()) != null) {
  
                  if (frame1 != null) filter.push(frame1);
  
                  frame3 = filter.pull();
  
                  //recorder.record(frame1);
  
                  recorder.record(frame3, avutil.AV_PIX_FMT_YUV420P);
  
                  recorder.record(frame2, avutil.AV_PIX_FMT_YUV420P);
  
              }
  
  
  
              recorder.stop();
  
              grabber1.stop();
  
              grabber2.stop();
  
              filter.stop();
  
  
  
          } catch (Exception e) {
  
              strReturn = Enum.Result.KO;
  
              ExceptionHandler.logException(e);
  
          }
  
      }
  
  
  
      return strReturn;
  
  }

• reduce all image in zip to be under fix (KB) using Imagemagick convert

  28 mars 2019, par VitalyT

  I’m using Imagemagick , i’m wondiring how i can reduce inside zip all f.e jpg images inside and change their size be under 40K.

  Till now i’ve tried

  according :

  https://gist.github.com/rkbhochalya/d3557a9d122ab547c040af3adbd565c2

   find . -name "*.jpg" -exec convert -define jpeg:extent=40kb "{}" -sampling-factor 4:2:0 -strip -colors 16 -depth 8  -define jpeg:extent=38kb "{}" \; -exec echo "{}" \;

  but it only reduces bit rate and colors to 16 that is ok , but not enough.

  tried magick mogrify -strip -colors 16 -depth 8 -quality 90  assets/*.jpg

  but still I need to reduce under 40K each image

  

  thanks,