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• Moviepy - Video background issue

  2 novembre 2015, par Harpreet Gill

  I have two video clips - Video1 and Video2. I want to place Video2 at a certain position of Video1, at a specific time. I am able to do it, but my problem is that Video2 has dark-black background, which appears in the final (output) video.

  Is there any option I can make Video2’s background transparent ?

• Issue in recording video

  16 novembre 2015, par human123

  I am trying to record video in 480*480 resolution like in vine using javacv. As a starting point I used the sample provided in https://github.com/bytedeco/javacv/blob/master/samples/RecordActivity.java Video is getting recorded (but not in the desired resolution) and saved.

  But the issue is that 480*480 resolution is not supported natively in android. So some pre processing needs to be done to get the video in desired resolution.

  So once I was able to record video using code sample provided by javacv, next challenge was on how to pre process the video. On research it was found that efficient cropping is possible when final image width required is same as recorded image width. Such a solution was provided in the SO question,Recording video on Android using JavaCV (Updated 2014 02 17). I changed onPreviewFrame method as suggested in that answer.

      @Override
  
      public void onPreviewFrame(byte[] data, Camera camera) {
  
          if (audioRecord == null || audioRecord.getRecordingState() != AudioRecord.RECORDSTATE_RECORDING) {
  
              startTime = System.currentTimeMillis();
  
              return;
  
          }
  
          if (RECORD_LENGTH > 0) {
  
              int i = imagesIndex++ % images.length;
  
              yuvImage = images[i];
  
              timestamps[i] = 1000 * (System.currentTimeMillis() - startTime);
  
          }
  
          /* get video data */
  
          imageWidth = 640;
  
          imageHeight = 480    
  
          int finalImageHeight = 360;
  
          if (yuvImage != null && recording) {
  
              ByteBuffer bb = (ByteBuffer)yuvImage.image[0].position(0); // resets the buffer
  
              final int startY = imageWidth*(imageHeight-finalImageHeight)/2;
  
              final int lenY = imageWidth*finalImageHeight;
  
              bb.put(data, startY, lenY);
  
              final int startVU = imageWidth*imageHeight + imageWidth*(imageHeight-finalImageHeight)/4;
  
              final int lenVU = imageWidth* finalImageHeight/2;
  
              bb.put(data, startVU, lenVU);
  
              try {
  
                  long t = 1000 * (System.currentTimeMillis() - startTime);
  
                  if (t > recorder.getTimestamp()) {
  
                      recorder.setTimestamp(t);
  
                  }
  
                  recorder.record(yuvImage);
  
              } catch (FFmpegFrameRecorder.Exception e) {
  
                  Log.e(LOG_TAG, "problem with recorder():", e);
  
              }
  
          }
  
  
  
  
  
      }
  
  }

  Please also note that this solution was provided for an older version of javacv. The resulting video had a yellowish overlay covering 2/3rd part. Also there was empty section on left side as the video was not cropped correctly.

  So my question is what is the most appropriate solution for cropping videos using latest version of javacv ?

  Code after making change as suggested by Alex Cohn

      @Override
  
      public void onPreviewFrame(byte[] data, Camera camera) {
  
          if (audioRecord == null || audioRecord.getRecordingState() != AudioRecord.RECORDSTATE_RECORDING) {
  
              startTime = System.currentTimeMillis();
  
              return;
  
          }
  
          if (RECORD_LENGTH > 0) {
  
              int i = imagesIndex++ % images.length;
  
              yuvImage = images[i];
  
              timestamps[i] = 1000 * (System.currentTimeMillis() - startTime);
  
          }
  
          /* get video data */
  
          imageWidth = 640;
  
          imageHeight = 480;       
  
          destWidth = 480;
  
  
  
          if (yuvImage != null && recording) {
  
              ByteBuffer bb = (ByteBuffer)yuvImage.image[0].position(0); // resets the buffer
  
              int start = 2*((imageWidth-destWidth)/4); // this must be even
  
              for (int row=0; row2; row++) {
  
                  bb.put(data, start, destWidth);
  
                  start += imageWidth;
  
              }
  
              try {
  
                  long t = 1000 * (System.currentTimeMillis() - startTime);
  
                  if (t > recorder.getTimestamp()) {
  
                      recorder.setTimestamp(t);
  
                  }
  
                  recorder.record(yuvImage);
  
              } catch (FFmpegFrameRecorder.Exception e) {
  
                  Log.e(LOG_TAG, "problem with recorder():", e);
  
              }
  
          }
  
  
  
  
  
      }

  Screen shot from video generated with this code (destWidth 480) is

  

  Next I tried capturing a video with destWidth speciified as 639. The result is

  

  When destWidth is 639 video is repeating contents twice. When it is 480, contents are repeated 5 times and the green overlay and distortion is more.

  Also When the destWidth = imageWidth, video is captured properly. ie, for 640*480 there is no repetition of video contents and no green overlay.

  Converting frame to IplImage

  When this question was asked first, I missed to mention that the record method in FFmpegFrameRecorder is now accepting object of type Frame whereas earlier it was IplImage object. So I tried to apply Alex Cohn’s solution by converting Frame to IplImage.

  //---------------------------------------
  
  // initialize ffmpeg_recorder
  
  //---------------------------------------
  
  private void initRecorder() {
  
  
  
      Log.w(LOG_TAG,"init recorder");
  
  
  
      imageWidth = 640;
  
      imageHeight = 480; 
  
  
  
      if (RECORD_LENGTH > 0) {
  
          imagesIndex = 0;
  
          images = new Frame[RECORD_LENGTH * frameRate];
  
          timestamps = new long[images.length];
  
          for (int i = 0; i < images.length; i++) {
  
              images[i] = new Frame(imageWidth, imageHeight, Frame.DEPTH_UBYTE, 2);
  
              timestamps[i] = -1;
  
          }
  
      } else if (yuvImage == null) {
  
          yuvImage = new Frame(imageWidth, imageHeight, Frame.DEPTH_UBYTE, 2);
  
          Log.i(LOG_TAG, "create yuvImage");
  
          OpenCVFrameConverter.ToIplImage converter = new OpenCVFrameConverter.ToIplImage();
  
          yuvIplimage = converter.convert(yuvImage);
  
  
  
      }
  
  
  
      Log.i(LOG_TAG, "ffmpeg_url: " + ffmpeg_link);
  
      recorder = new FFmpegFrameRecorder(ffmpeg_link, imageWidth, imageHeight, 1);
  
      recorder.setFormat("flv");
  
      recorder.setSampleRate(sampleAudioRateInHz);
  
      // Set in the surface changed method
  
      recorder.setFrameRate(frameRate);
  
  
  
      Log.i(LOG_TAG, "recorder initialize success");
  
  
  
      audioRecordRunnable = new AudioRecordRunnable();
  
      audioThread = new Thread(audioRecordRunnable);
  
      runAudioThread = true;
  
  }
  
  
  
  
  
  
  
  @Override
  
      public void onPreviewFrame(byte[] data, Camera camera) {
  
          if (audioRecord == null || audioRecord.getRecordingState() != AudioRecord.RECORDSTATE_RECORDING) {
  
              startTime = System.currentTimeMillis();
  
              return;
  
          }
  
          if (RECORD_LENGTH > 0) {
  
              int i = imagesIndex++ % images.length;
  
              yuvImage = images[i];
  
              timestamps[i] = 1000 * (System.currentTimeMillis() - startTime);
  
          }
  
          /* get video data */
  
          int destWidth = 640;
  
  
  
          if (yuvIplimage != null && recording) {
  
              ByteBuffer bb = yuvIplimage.getByteBuffer(); // resets the buffer
  
              int start = 2*((imageWidth-destWidth)/4); // this must be even
  
              for (int row=0; row2; row++) {
  
                  bb.put(data, start, destWidth);
  
                  start += imageWidth;
  
              }
  
              try {
  
                  long t = 1000 * (System.currentTimeMillis() - startTime);
  
                  if (t > recorder.getTimestamp()) {
  
                      recorder.setTimestamp(t);
  
                  }
  
                  recorder.record(yuvImage);
  
              } catch (FFmpegFrameRecorder.Exception e) {
  
                  Log.e(LOG_TAG, "problem with recorder():", e);
  
              }
  
          }
  
  
  
  
  
      }

  But the videos generated with this method contained only green frames.

• FFmpeg Concat artefact between bribes

  3 février 2016, par Maypeur

  I use FFmpeg to concat 3 mp4 video bribes.

  FFbrope show all bribes start with a keyframes and play very well in VLC.

  When playing the final video file some artefact appears when a bribe start :

  ffmpeg.exe -f concat -i video_bribes.list -codec:v copy -acodec none -movflags faststart -y v_2.mp4

  I tried differents options in the concat command line to re encode but artefact are still here.

  What can i do to avoid this grey artefact between bribes ?

  Thanks.