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• How to force ffmpeg to refresh overlay image more often ?

  30 avril 2019, par Alex Fomin

  I am trying to do sports live-streaming using ffmpeg. Score of a streaming match is being fetched from server and converted to png. This png must appear on top of the video.

  ffmpeg allows to put an overlay over a video stream using image2 demuxer. If I use -loop1, this overlay updates approximately every 5 seconds. How can I force ffmpeg to read it from disk more often ?

  My current attempt with overlay updating once in 5 seconds(mp4 video for testing purposes) :

  nice -n -19 ffmpeg \
  
          -re -y \
  
          -i s.mp4 \
  
          -f image2 -loop 1 -i http://127.0.0.1:3000/img \
  
          -filter_complex "[0:v][1:v]overlay" \
  
          -threads 4 \
  
          -v 0 -f mpegts -preset ultrafast udp://127.0.0.1:23000 \
  
          &

  P.S
  I know, that I can make youtube streaming widget on the website and put score on top of it just using html/css/js. But unfortunately it must be done directly in the video stream.

  P.P.S
  I know, that I can use ffmpeg drawtext. But it is not what I want. I have specially designed png, which must be updated as frequently, as possible ( once in 1-2 seconds would be just great )

• Using FFMPEG I get an error when trying to insert a fade after about 35 mins in a long video - is this possible ?

  8 avril 2019, par Matt Gardiner

  I have a source video that is an hour long from which I want to extract a couple of minutes towards the end and add a video fade in at the start of the cropped section.

  Using FFMPEG, I’m specifying the following command :

  ffmpeg -i MyLongVideo.mp4 -q:v 0 -y -ss 00:50:00.000 -to 00:52:00.000 -vf "fade=t=in:st=3000.0:d=1.0, scale=iw*min(1280/iw\,720/ih):ih*min(1280/iw\,720/ih),pad=1280:720:(1280-iw)/2:(720-ih)/2" ./testoutput.ts

  This is intended to crop from the source video from 50:00.000 to 52:00.00 and fade in from the 50th minute for 0.5 seconds (so at 3000 seconds in - st=3000.0).

  This command that we build programmatically, works on shorter videos or when you crop from before about 35 minutes. For this longer video though I get an error that says :

  [fade @ 0000025399981e80] Value 3000.000000 for parameter 'st' out of range [0 - 2147.48]

  The 2147.48 is around the 35 minutes in seconds which explains why this command works for shorter videos or on crops earlier than 35 minutes.

  I’ve seen a number of other issues with FFMPEG talking about this ’magic’ 2147.48 number with parameter values. Is this some sort of hard limit ?

  Is there a way to do what I want to do ? I could do this in two passes - extract the section of video and then add the fade, but I’d rather do it in one command if possible - and it works for shorter/earlier crops.

• Nodejs spawn - child processes

  24 février 2019, par z Eyeland

  My nodejs application is running on raspberry Pi. The program uses spawn child process to trigger bash scripts which record or compress the previous recorded file. The program records fine. After recording the user selects the compress button. This kills the recording spawn process and fires the bash script for compression. The issue I am having is that whenever the video length gets around 1min long the compression spawn process times out or something. I ran ps -ef to view all process and i noticed that the compression script is still there. She the video length is short - the compression spawn process completes its cycle and send api request to shutdown the process. Here is some code

  Api with console log that lets me know when compression is done. When the video clips are longer around 1min this GET request never logs’=

  app.get('/clovis/api/led', function (req, res){
  
  console.log("api activated for resetLED function");
  
  resetLED();
  
  console.log("reset was completed");
  
  })

  Nodejs spawns that call different bash scripts

  function setBashScript(scriptNum){
  
  if(scriptNum == 0){
  
      //do this
  
       child = spawn('./feedmpeg.sh');
  
   resetLED();
  
  }
  
  if(scriptNum == 1){
  
      //do this
  
      updatePicturePath();
  
       child = spawn('./feedSnapshot.sh',[pictureFilePath]);
  
  resetLED();
  
  }
  
  if(scriptNum == 2){
  
      //do this
  
      updateVideoPath();
  
      child = spawn('./feedmpegRecord.sh',[videoFilePath]);
  
      isRecording = true;
  
  resetLED();
  
  ledRed();
  
  }
  
  if(scriptNum == 10){
  
      //do this
  
      updateCompressedPath();
  
       child = spawn('./generalCompressionMP4.sh',[videoFilePath,compressedFilePath]);
  
       isRecording = false;
  
   resetLED();
  
   ledBlue();
  
    }
  
    }

  generalCompressionMP4.sh - The spawn process that doesnt complete if video length is too long. Generally when the process is complete, I head over to the localhost server and view the mp4 file. When this issue occures the mp4 doesnt load, the old path is not removed, and the api doesnt send.

  #!/bin/bash
  
  FILEPATH="$1"
  
  COMPRESSIONPATH="$2"
  
  ffmpeg -i $FILEPATH -vcodec h264 -acodec mp2 $COMPRESSIONPATH
  
  sudo rm $FILEPATH
  
  curl -H "Content-Type: application/json" -X POST 
  
  http://localhost:3000/clovis/api/led

  Why might the process get stuck ? How can i fix this ? Should I not use spawn child process ?