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• 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

• 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 ?

  


• Streaming Video from RTMP to EMGUCV

  22 juillet 2017, par Isuru

  I’m trying to stream a webcam using RTMP to an EMGUCV project in order to process the video. I have set up a private RTMP server in a linux box using this tutorial,
  https://obsproject.com/forum/resources/how-to-set-up-your-own-private-rtmp-server-using-nginx.50/

  I’m testing the webcam stream using ffmpeg with the following commands,

  • Write to the rtmp server using,

    ffmpeg -y -f vfwcap -framerate 25 -video_size 640x480 -i 0 -an -f flv rtmp://rtmp-server:1935/live/stream

  • Read from the rtmp server using,
    ffplay -fflags nobuffer rtmp ://rtmp-server:1935/live/stream -loglevel verbose

  I’m able to write a simple OpenCV C++ application to read the stream and display it. Code below,

      cv::VideoCapture vcap;
  
      cv::Mat image;
  
      const std::string videoStreamAddress = "rtmp://rtmp-server:1935/live/stream";
  
      if(!vcap.open(videoStreamAddress)) {
  
          printf("Error opening video stream or file");
  
          return -1;
  
      }
  
  
  
      cv::namedWindow("Output Window");
  
      cv::Mat edges;
  
      for(;;) {
  
          if(!vcap.read(image)) {
  
              printf("No frame");
  
              cv::waitKey();
  
          }
  
          cv::imshow("Output Window", image);
  
          if(cv::waitKey(1) >= 0) break;
  
      }
  
  return 0;

  The above code works properly. However when I try it using EMGUCV C#, I get the error message
  unable to create to capture from rtmp://rtmp-server:1935/live/stream

  This is my C# Code,

      public partial class MainForm : Form
  
      {
  
          private static Capture _cameraCapture;
  
  
  
          public MainForm()
  
          {
  
              InitializeComponent();
  
              Run();
  
          }
  
  
  
          void Run()
  
          {
  
              try
  
              {
  
                  _cameraCapture = new Capture("rtmp://192.168.56.101:1935/live/stream");                
  
              }
  
              catch (Exception e)
  
              {
  
                  MessageBox.Show(e.Message);
  
                  return;
  
              }            
  
          }
  
     }

  Do I need a specific build of EMGUCV with FFMPEG or is RTMP capturing not available in EMGUCV ?