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• Ffmpeg output stream closed

  29 novembre 2023, par excalibur

  There is one problem in my code that uses ffmpeg to convert webm videos to mp4 and set duration to 10 seconds, it works well but, sometimes returns "output Stream closed" error. What can be a reason of this problem, and how can i solve it ?

  


  My code :

  


  async convertWebmVideoToMp4(buffer: any) {
    try {
        return new Promise((resolve, reject) => {
            const videoMp4Buffer = Buffer.from(buffer);

            const readable = Readable.from(videoMp4Buffer);

            const outputBuffer = [];

            const outputStream = new Writable({
                write(chunk, encoding, callback) {
                    outputBuffer.push(chunk);
                    callback();
                },
            });

            const ffmpegProcess = ffmpeg()
                .input(readable)
                .outputFormat('mp4')
                .videoCodec('libx264')
                .audioCodec('aac')
                .duration(10)
                .outputOptions([
                    '-movflags frag_keyframe+empty_moov',
                    '-preset ultrafast',
                    '-c:a aac',
                    '-r 30',
                    '-tune fastdecode',
                ])
                .on('end', () => {
                    outputStream.end();
                    const finalOutputBuffer = Buffer.concat(outputBuffer);
                    resolve(finalOutputBuffer);
                })
                .on('error', (err, stdout, stderr) => {
                    console.error(err);
                    reject(err);
                });

            outputStream.on('error', err => {
                this.logger.error(err);
            });

            ffmpegProcess.pipe(outputStream, { end: true });
        });
    } catch (error) {
        throw error;
    }
}


  


  My code should return the buffer of video that type is mp4 and length is 10 seconds, but it returns "output stream closed" error.

  


• How to stop perl buffering ffmpeg output

  4 février 2017, par Sebastian King

  I am trying to have a Perl program process the output of an ffmpeg encode, however my test program only seems to receive the output of ffmpeg in periodic chunks, thus I am assuming there is some sort of buffering going on. How can I make it process it in real-time ?

  My test program (the tr command is there because I thought maybe ffmpeg’s carriage returns were causing perl to see one big long line or something) :

  #!/usr/bin/perl
  
  
  
  $i = "test.mkv"; # big file, long encode time
  
  $o = "test.mp4";
  
  
  
  open(F, "-|", "ffmpeg -y -i '$i' '$o' 2>&1 | tr '\r' '\n'")
  
          or die "oh no";
  
  
  
  while(<f>) {
  
          print "A12345: $_"; # some random text so i know the output was processed in perl
  
  }
  
  </f>

  Everything works fine when I replace the ffmpeg command with this script :

  #!/bin/bash
  
  
  
  echo "hello";
  
  
  
  for i in `seq 1 10`; do
  
          sleep 1;
  
          echo "hello $i";
  
  done
  
  
  
  echo "bye";

  When using the above script I see the output each second as it happens. With ffmpeg it is some 5-10 seconds or so until it outputs and will output sometimes 100 lines each output.

  I have tried using the program unbuffer ahead of ffmpeg in the command call but it seems to have no effect. Is it perhaps the 2>&1 that might be buffering ?
  Any help is much appreciated.

  If you are unfamiliar with ffmpeg’s output, it outputs a bunch of file information and stuff to STDOUT and then during encoding it outputs lines like

  frame=  332 fps= 93 q=28.0 size=     528kB time=00:00:13.33 bitrate= 324.2kbits/s speed=3.75x

  which begin with carriage returns instead of new lines (hence tr) on STDERR (hence 2>&1).

• Capturing network video using opencv

  3 septembre 2014, par Subhendu Sinha Chaudhuri

  I am using ffserver and ffmpeg combination to capture web camera video and transmit it through my network.

  I want to capture this video using opencv and python from another computer.
  I can see the video (cam1.asf) in the browser of another computer. But my opencv + python code could not capture any frame.

  Code for ffserver

  HTTPPort 8090
  
  HTTPBindAddress 0.0.0.0
  
  MaxHTTPConnections 2000
  
  MaxClients 1000
  
  MaxBandWidth 2000
  
  
  
  <feed>
  
     File ./tmp/feed1.ffm
  
     FileMaxSize 1G
  
     ACL allow 127.0.0.1
  
  </feed>
  
  
  
  <stream>
  
    Feed feed1.ffm
  
    Format asf
  
    VideoCodec msmpeg4v2
  
    VideoFrameRate 30
  
    VideoSize vga
  
  </stream>

  FFmpeg

  $ffmpeg -f video4linux2 -i /dev/video0 192.168.1.3 /cam1.ffm

  This stream can be seen in the browser

  But with opencv code

  import sys
  
  import cv2.cv as cv
  
  import numpy
  
  
  
  video="http://http://192.168.1.3:8090/cam1.asf"
  
  capture =cv.CaptureFromFile(video)
  
  cv.NamedWindow('Video Stream', 1 )
  
  while True:
  
    # capture the current frame
  
    frame = cv.QueryFrame(capture)
  
    #if frame is None:
  
     # break
  
    #else:
  
      #detect(frame)
  
    cv.ShowImage('Video Stream', frame)
  
    if cv.WaitKey(10) == 27:
  
      print 'ESC pressed. Exiting ...'
  
      break

  I donot get any output in the stream

  My aim is to work with the web camera video both at the base station (ie where the web camera is connected) and also at the network location