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• FFMPEG and JNI - pass AVFrame data to Java and Back

  17 octobre 2015, par tishu

  I have some C code that decodes a video frame by frame. I get to a point where i have an AVFrame in BGR32 and would like to send it back to Java for editing.

  I have a ByteBuffer object in my C code that was created in Java using AllocateDirect but i struggle to write the content of the AVFrame->data[0] (of uint8_t type) to it and read it back. I have tried memcpy with no luck. Does anyone have an idea how to achieve this ?

  UPDATE
  Followed Will’s comment below and wrote this in C

  char *buf = (*pEnv)->GetDirectBufferAddress(pEnv, byteBuffer);
  
  memcpy(buf, rgb_frame->data[0], output_width*output_height*4);

  The buffer does contain some data in Java but doing the following returns a null bitmap

  BufferedImage frame = ImageIO.read(bitmapStream);

  Where bitmapStream is a ByteBufferInputStream defined here :
  https://code.google.com/p/kryo/source/browse/trunk/src/com/esotericsoftware/kryo/io/ByteBufferInputStream.java?r=205

  Not sure if I am not writing things correctly in this buffer

  UPDATE 2

  Got pretty close now thanks to the latest snippet. I am using BGR32 format in my C code ie 4 bytes per pixel. So I modified things a bit in Java :

  final byte[] dataArray = new byte[width*height*4];
  
  imageData.get(dataArray);
  
  final BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
  
  final DataBuffer buffer = new DataBufferByte(dataArray, dataArray.length);
  
  Raster raster = Raster.createRaster(sampleModel, buffer, null);
  
  image.setData(raster);

  I get the image correctly but there seems to be an issue with color channels
  

  Tried different formats with no luck

• ffmpeg scale down video dynamically (squeeze-back) or zoompan out to smaller than original VER2

  19 juillet 2023, par loarrin

  I have 2 videos, I'm trying to overlay one on top of the other, and have it shrink down in an animated fashion until it appears like a picture-in-picture setup. Then, after a few seconds it should scale back up. Just like in this question. Here is the working code from there :

  


  ffmpeg -i bg.mov -i top.mov -filter_complex "[0:v]scale=1920x1080,setpts=PTS-STARTPTS[bg]; [1:v]setpts=PTS-STARTPTS+2/TB, scale=-1:'480+600*abs(sin((t-2)*2*PI/8))':eval=frame[top]; [bg][top]overlay" -vcodec libx264 out.mp4


  


  It works perfectly, but I have one difference I cannot achieve modifying existing code : scale filter in this example resizes the second video stream having attraction point in the top left corner of this stream. I mean, when the second stream is getting smaller, it is scaled to the top left corner. And if it is getting bigger, it again stretches from the top left corner. The top left corner of the stream being scaled is staying in one place constantly no matter what.

  


  Is it possible to make more symmetrical version of this scale code, so when the second stream is scaled it is scaled from and to the top center of it (So the top left corner would move right when the stream is getting smaller and move to the left then the stream is getting bigger) ?

  


  

  


• FFmpeg video to still images and back to video lossless

  28 novembre 2012, par Rigoni

  I'm trying to extract an image from an uncompressed AVI video using FFmpeg with the command :

  ffmpeg -i sorce.avi -f image2 -pix_fmt bgr24 images/%1d.bmp

  All is okay, but now I need to convert these images back to a video file.
  I'm trying using this command :

  ffmpeg -f image2 -r 24 -i marked/%1d.bmp -y -vcodec ffv1 -pix_fmt bgr24 test.avi

  But the output video is compressed and poor quality.

  Is there any way to extract the images in RGB format and than back to a lossless video ?

  I also tryed to use -vcodec rawvideo, but the quality still bad.