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• Understanding a script which uses ffmpeg to send rtmp input to node.js script

  4 juin 2022, par Arpit Shukla

  I was trying to understand this shell script which uses ffmpeg to take an rtmp input stream and send it to a node.js script. But I am having trouble understanding the syntax. What is going on here ?

  


  The script :

  


  while :
do
  echo "Loop start"

  feed_time=$(ffprobe -v error -show_entries format=start_time -of default=noprint_wrappers=1:nokey=1 $RTMP_INPUT)
  printf "feed_time value: ${feed_time}"

  if [ ! -z "${feed_time}" ]
  then
  ffmpeg -i $RTMP_INPUT -tune zerolatency -muxdelay 0 -af "afftdn=nf=-20, highpass=f=200, lowpass=f=3000" -vn -sn -dn -f wav -ar 16000 -ac 1 - 2>/dev/null | node src/transcribe.js $feed_time

  else
  echo "FFprobe returned null as a feed time."
  
  fi

  echo "Loop finish"
  sleep 3
done


  


  

  • What is feed_time here ? What does it represent ?

  


  • What is this portion doing - 2>/dev/null | node src/transcribe.js $feed_time ?

  


  • What is the use of sleep 3 ? Does this mean that we are sending audio stream to node.js in chuncks of 3 seconds ?

  


  


• Need help understanding this script which uses ffmpeg to send rtmp input to node.js script

  4 juin 2022, par Arpit Shukla

  I was trying to understand this shell script which uses ffmpeg to take an rtmp input stream and send it to a node.js script. But I am having trouble understanding the syntax. Can someone please explain what is going on here ?

  


  The script :

  


  while :
do
  echo "Loop start"

  feed_time=$(ffprobe -v error -show_entries format=start_time -of default=noprint_wrappers=1:nokey=1 $RTMP_INPUT)
  printf "feed_time value: ${feed_time}"

  if [ ! -z "${feed_time}" ]
  then
  ffmpeg -i $RTMP_INPUT -tune zerolatency -muxdelay 0 -af "afftdn=nf=-20, highpass=f=200, lowpass=f=3000" -vn -sn -dn -f wav -ar 16000 -ac 1 - 2>/dev/null | node src/transcribe.js $feed_time

  else
  echo "FFprobe returned null as a feed time."
  
  fi

  echo "Loop finish"
  sleep 3
done


  


  

  • What is feed_time here ? What does it represent ?

  


  • What is this portion doing - 2>/dev/null | node src/transcribe.js $feed_time ?

  


  • What is the use of sleep 3 ? Does this mean that we are sending audio stream to node.js in chuncks of 3 seconds ?

  


  


• ffmpeg app using node occasionally crashes as file doesn't appear to be read correctly

  31 mai 2022, par Zabs

  I have an simple Node application that allows me to pass an AWS S3 URL link to a file (in this case video files). It uses the FFMPEG library to read the video file and return data like codecs, duration, bitrate etc..

  


  The script is called from PHP script which in turn send the data to the Node endpoint and passes the Amazon S3 URL to node. Sometimes for no obvious reasons the video file fails to return the expected values regarding container, codec, duration etc... and just returns '0'. But when I try the exact same file/request again it returns this data correctly e.g container:mp4

  


  I'm not sure but I think the script somehow needs the createWriteStream to be closed but I cannot be sure, the problem is the issue I have found doesn't happen all the time but sporadically so its hard to get to the issue when its difficult to replicate it.

  


  Any ideas ?

  


  router.post('/', async function(req, res) {
  const fileURL = new URL(req.body.file);
  var path = fileURL.pathname;
  path = 'tmp/'+path.substring(1);    // removes the initial / from the path

  let file = fs.createWriteStream(path);  // create the file locally
  const request = https.get(fileURL, function(response) {
    response.pipe(file);
  });
  
  // after file has saved
  file.on('finish', function () {
    var process = new ffmpeg(path);
    process.then(function (video) {
      let metadata = formatMetadata(video.metadata);

      res.send ({
        status: '200',
        data: metadata,
        errors: errors,
        response: 'success'
      });

    }, function (err) {
      console.warn('Error: ' + err);

      res.send ({
        status: '400',
        data: 'Something went wrong processing this video',
        response: 'fail',
      });
    });
  });

  file.on('error', function (err) {
    console.warn(err);
  });

});

function formatMetadata(metadata) {
  const data = {
    'video' : metadata.video,
    'audio' : metadata.audio,
    'duration' : metadata.duration
  };
  return data;
}


  


  // Expected output

  


  {"data":{"video":{"container":"mov","bitrate":400,"stream":0,"codec":"h264","resolution":{"w":1280,"h":720},"resolutionSquare":{"w":1280,"h":720},"aspect":{"x":16,"y":9,"string":"16:9","value":1.7777777777777777},"rotate":0,"fps":25,"pixelString":"1:1","pixel":1},"audio":{"codec":"aac","bitrate":"127","sample_rate":44100,"stream":0,"channels":{"raw":"stereo","value":2}},"duration":{"raw":"00:00:25.68","seconds":25}}


  


  // Actual output

  


  {"data":{"video":{"container":"","bitrate":0,"stream":0,"codec":"","resolution":{"w":0,"h":0},"resolutionSquare":{"w":0,"h":null},"aspect":{},"rotate":0,"fps":0,"pixelString":"","pixel":0},"audio":{"codec":"","bitrate":"","sample_rate":0,"stream":0,"channels":{"raw":"","value":""}},"duration":{"raw":"","seconds":0}}


  


  Note - this happens sporadically