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• FFMPEG - Extract sequence while recording

  26 février 2020, par Vincent Carretero

  I have a ffmpeg process to record a webcam, thats very classic...
  I would like to extract a sequence from the recording file before the end of the record.

  example :
   my recording start at 10:00 am and finish at 11:00 am
   at 10:15 am, an event append, and an operator need to watch it quickly,
   i would like to extract the sequence, and than he can watch at 10:20 am (but the video still recording and the Mp4.file not ended).

  is that possible ?

  thanks !!

• How to fix 'Error : Write EOF' when running a nodejs file which spawns a child process running ffmpeg ?

  16 septembre 2022, par Prithivin Lakshminarayanan

  I am new to nodejs scripting and I am trying to create a program which receives a video file as a buffer and creates a thumbnail from it. This is my code :

  


  create_thumbnail.js :

  


  const { Readable } = require('stream');
const child_process = require('node:child_process');

async function generate_thumbnail(videoFile, callback) {

    const readable = new Readable();
    readable._read = () => {}
    readable.push(videoFile.data)
    readable.push(null)
    const ffmpeg = child_process.spawn('C:\\FFmpeg\\bin\\ffmpeg', ['-i', 'pipe:0', '-vframes', '1', '-vf', 'scale=iw*.5:ih*0.5', '-f', 'mjpeg', 'pipe:1'], { stdio: ['pipe', 'pipe', 'ignore'] })
    readable.pipe(ffmpeg.stdin);

    const buffer = [];

    ffmpeg.stdout.on('data', (data) => {
        buffer.push(data);
    });

    const thumbnail = ffmpeg.stdout.on('end', () => {
        console.log('There will be no more data.');
        var buf = Buffer.concat(buffer);
        callback (buf);
    });
}

module.exports = { generate_thumbnail };


  


  The program is creating a thumbnail successfully for a video which has a few seconds length. It is failing for larger videos with the following error :

  


  node:events:368
      throw er; // Unhandled 'error' event
      ^

Error: write EOF
    at WriteWrap.onWriteComplete [as oncomplete] (node:internal/stream_base_commons:98:16)
Emitted 'error' event on Socket instance at:
    at Socket.onerror (node:internal/streams/readable:773:14)
    at Socket.emit (node:events:390:28)
    at emitErrorNT (node:internal/streams/destroy:157:8)
    at emitErrorCloseNT (node:internal/streams/destroy:122:3)
    at processTicksAndRejections (node:internal/process/task_queues:83:21) {
  errno: -4095,
  code: 'EOF',
  syscall: 'write'


  


  Can someone please let me know the reason for getting this error. How can I fix it ?

  


• ffmpeg replacing audio track with track from another video but different length (sync audio)

  27 août 2019, par Matt

  Background

  I have digitized some old Canon Video8 tapes. I used a SONY Digital8 camera (which is backwards compatible with Video8) to output DV (using it’s inbuilt ADC). The conversion process worked well for the video but the audio came through jumpy/distorted in places. This left me with a problem, was it the Camera or the tape ? So I bought another Samsung Video8 camera (just analog) and using the SONY’s passthrough feature output from the Samsung (Composite & mono audio) into the SONY which output the DV. Much to my delight it worked ! The audio was clear.

  Result

  DV01.avi - Good Video / Crap Audio
  
  DV02.avi - Crap Video / Good Audio

  Ok so obviously what I would like to do is take the video track from DV01 and the audio track from DV02 and join/mux ? them WITHOUT re-encoding.

  Problem 1 : They have different start times so just copying over the audio track will result it not being in sync.

  After some googling I found you can use ffmpeg to take care of this :

  Firstly here is the Video info using : ffmpeg -i DV01.avi

  Input #0, avi, from 'DV01.avi':
  
    Duration: 02:53:06.68, start: 0.000000, bitrate: 28878 kb/s
  
      Stream #0:0: Video: dvvideo, yuv420p, 720x576 [SAR 16:15 DAR 4:3], 25000 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
  
      Stream #0:1: Audio: pcm_s16le, 32000 Hz, stereo, s16, 1024 kb/s
  
      Stream #0:2: Audio: pcm_s16le, 32000 Hz, stereo, s16, 1024 kb/s

  Muxing :

  ffmpeg -itsoffset 4 -i DV01.avi -i DV02.avi -map 0:v -map 1:a -c copy output.avi

  In the example above I am delaying the start of the video 4 seconds (I think ?) This is just an example I haven’t actually tried it as the file sizes are 40Gb !

  So my QUESTION is :

  Given the background above what would be the best way to join/mux the two streams together (without re-encoding) with the audio being in sync. Given that syncing the audio to the video may need millisecond tweaking I don’t believe trial and error is a good idea (I don’t want to tweak it by 10ms then rinse and repeat for a 40Gb file) ?

  I just had a thought, could I say create a 10 second clip (from the start) of each video and use them to find the reference/sync start point then use that when muxing the 40Gb versions ?

  Anyway, you get the idea. Looking for ways to solve this problem. Thanks !