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• Issue with image rotation using JavaCV library

  26 février 2015, par intrepidkarthi

  I am writing an Android application which records video for a specified amount of time. Everything works fine if I record using the smartphone’s back camera. The app has a feature to pause/record feature like in Vine app. The issue comes when recording using the device’s front camera. The video surface frame looks fine when storing/playing the video the video is upside down. There is a lot of things discussed about this issue everywhere. But I didn’t find any solution that WORKS.

  Have a look at the code and image mentioned below.

  Here is the original image taken from front camera. I have turned it upside down for a better view.

  

  Here is what I actually get after rotation :

  

  Method :

       IplImage copy = cvCloneImage(image);
  
       IplImage rotatedImage = cvCreateImage(cvGetSize(copy), copy.depth(), copy.nChannels());
  
       //Define Rotational Matrix
  
       CvMat mapMatrix = cvCreateMat(2, 3, CV_32FC1);
  
  
  
       //Define Mid Point
  
       CvPoint2D32f centerPoint = new CvPoint2D32f();
  
       centerPoint.x(copy.width() / 2);
  
       centerPoint.y(copy.height() / 2);
  
  
  
       //Get Rotational Matrix
  
       cv2DRotationMatrix(centerPoint, angle, 1.0, mapMatrix);
  
  
  
       //Rotate the Image
  
       cvWarpAffine(copy, rotatedImage, mapMatrix, CV_INTER_CUBIC + CV_WARP_FILL_OUTLIERS, cvScalarAll(170));
  
       cvReleaseImage(copy);
  
       cvReleaseMat(mapMatrix);

  I have tried doing

       double angleTemp = angle;
  
  
  
       angleTemp= ((angleTemp / 90)%4)*90;       
  
       final int number = (int) Math.abs(angleTemp/90);
  
  
  
       for(int i = 0; i != number; ++i){            
  
           cvTranspose(rotatedImage, rotatedImage);
  
           cvFlip(rotatedImage, rotatedImage, 0);           
  
       }

  Ends up in throwing exception saying that source and destination doesn’t match with number of columns and rows.

  Update :

  Video is recorded in this way.

  IplImage newImage = null;
  
  if(cameraSelection == CameraInfo.CAMERA_FACING_FRONT){
  
      newImage = videoRecorder.rotate(yuvIplImage, 180);
  
      videoRecorder.record(newImage);
  
  }
  
  else
  
      videoRecorder.record(yuvIplImage);  

  Rotation is done in this way :

      IplImage img = IplImage.create(image.height(), image.width(),
  
              image.depth(), image.nChannels());
  
  
  
      for (int i = 0; i < 180; i++) {
  
          cvTranspose(image, img);
  
          cvFlip(img, img, 0);
  
      }

  Can anyone point out what is wrong here if you have experienced this before ?

• FFmpeg "faststart" flag with images to video

  22 août 2016, par Calvin W.

  I am using MoviePy to process my video and stream it.

  In MoviePy, it decode the input file to a frames * width * heigh * 3 (RGB values) NumPy array. And when it encode the video, it pass the NumPy array frame by frame to standard input of ffmpeg.

  In order to stream the video on-the-fly, I have to move the video header to the front.

  Is it posible to use faststart flag with such video encoding ?

• mp4 to hls ffmpeg during upload to Google storage

  13 février 2018, par Sofiia Vynnytska

  I have an API written on Java, which is used for uploading mp4 videos on front-end. We store those videos on google cloud and our application is running in google cloud. For Android clients, we need to convert uploaded videos to hls. Unfortunately, Google cloud does not have transcoder for videos and I need to convert video in another way. I found that ffmpeg can do this. But I cannot find a good solution for this and I need an advice.
  One of ideas is to deploy cloud function on google cloud, which will convert mp4 to hls after uploading video. Can I need to upload this m3u8 and ts videos to storage ? Will be this approach okay ? Is there any other possible solution ?