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• Create video with size based on image and place a video somewhere with an offset

  10 mars 2024, par NoKey

  I am trying out FFMPEG and I am unsure how hard it is to do what I want. I have some device frames and I want to play a video inside the frame. For example, this is a device frame :

  


  

  


  Now I want to play a video within the screen of the iPhone. I already got the exact X and Y offset where the video must be placed to show it correctly. I have the following challenges to make it work, and I want to make sure FFMPEG can do it before I spend to much time reinventing the wheel :

  


  


  • The output of the video must be as big as the PNG. This is already a
confusing part for me. I have the width and height already available,
but the things I saw is that FFMPEG will take over the input of the
video as final size. The final output of the video should of course
be the length of the input video.

    


  


  • The background must be transparant (so no black background, I want to
play the video on top of a website so it's nice if it's transparant and the corners are not black).

    


  


  • The ability to place a video somewhere with a specified X and Y
offset inside the device frame.

    


  


  • Not sure if it's possible in the same command, but maybe the video
needs to be resized to make it fit. I got the exact dimensions for
the video.

    


  


  


  The things I struggle most is point 1 where the output video must have a transparant background and where the device frame is placed in. Does anybody got tips ?

  


• delay in lyrics shown when concat video with lyrics with an intro video using ffmpeg

  19 mars 2018, par no name

  I have a video with lyrics I add the lyrics used ffmpeg too. I have the lyrics in lrc formate and i change it to ass lyrics formate then I start to add it to my video using this command

  ffmpeg -i video.mp4 -vf "ass=out.ass,fade=in:0:30" -y amr.mp4

  I use fade=in:0:30 to make fade in the start of the video so when I start merge intro video my original video not start at once but to have some fade in, in the start to have a good view.
  then I start to add the intro video using a text file which has this

  file intro.mp4
  
  file amr.mp4

  then I merge them using this command

  ffmpeg -f concat -safe 0 -i out.txt -c copy -y final.mp4

  i got these message

  [mov,mp4,m4a,3gp,3g2,mj2 @ 03eadb80] Auto-inserting h264_mp4toannexb bitstream filter
  
  [mp4 @ 06419580] Non-monotonous DTS in output stream 0:1; previous: 310272,     current: 285626; changing to 310273. This may result in incorrect timestamps in   the output file.

  repeated many times.
  when i watch the final video the lyrics have some delay from the sound the problem appeared when I merge the intro video but without it the lyrics have no problem so what I made wrong make the lyrics shown in this way and not in the right timing as it should have no problems as I merge only the intro video and after add the lyrics to the original one
  Thanks in advance

• 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