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• ffmpeg record video from image pipe with constant framerate

  4 janvier 2023, par Michael

  I'm trying to record a lossless video with ffmpeg, feeding it image data through standard input.

  


  The process is started like this (C#) :

  


  string inputArgs = "-y -f image2pipe -pix_fmt yuyv422 -i -";
string outputArgs = "-r 20 -c:v libx264 -crf 0 -pix_fmt yuv422p -preset ultrafast C:\\temp\\out.mp4";

process = new Process
{
    StartInfo =
        {
           FileName = "ffmpeg.exe",
           Arguments = $"{inputArgs} {outputArgs}",
           UseShellExecute = false,
           CreateNoWindow = true,
           RedirectStandardInput = true
        }
};

process.Start();


  


  The above works, but I have a problem with framerate. The rate I'm feeding images to ffmpeg is different over time, but I need ffmpeg to keep output rate constant. According to ffmpeg documentation, if set like this "-r 20" it should "duplicate or drop input frames to achieve constant output frame rate fps". But it doesn't. If I feed the images to the ffmpeg too slow, I'm getting fast playing video and vice versa.

  


  Am I providing wrong arguments ? Or it's somehow has to deal with ffmpeg getting images from Standard Input ?

  


  I tried these options in the output settings block : "vsync" (setting it to 1) and "fps_mode" (setting it to cfr). "vsync" doesn't have any effect, with "fps_mode" nothing works (video not recorded at all).

  


• bash script with conditional arguments and output pipe not working [duplicate]

  19 décembre 2022, par Pavel

  Can u please help me with bash script for ffmpeg ?
Trying to create condition based on args to play OR save media to file, so I've created this kind of IF :

  


  #!/bin/bash

if [ "$1" == "play" ]; then
    POSTFIX="-f matroska - | mpv -"
else
    POSTFIX="-y $OUTPUT"
fi

ffmpeg \
  # skipped personal ffmpeg stuff
  "$POSTFIX"


  


  Now when I try to run it with "play" argument it says :

  


  Unrecognized option 'f matroska - | mpv -'.


  


  So if I add this POSTFIX both variants to command everything works fine...

  


  It looks like something in my bash screens this args or something like that ? Also I don't see in error this dash symbol before f option

  


• NodeJS SpeechRecorder pipe to child process ffmpeg encoder - dest.on is not a function

  10 décembre 2022, par Matthew Swaringen

  Trying to make a utility to help me with recording words for something. Unfortunately getting stuck on the basics.

  


  The error I get when I hit s key and talk enough to fill the buffer is

  


  terminate called after throwing an instance of 'Napi::Error'
  what():  dest.on is not a function
[1]    2298218 IOT instruction (core dumped)  node record.js


  


  Code is below. I can write the wav file and then encode that but I'd rather not have to have an intermediate file unless there is no way around it, and I can't imagine that is the case.

  


  const { spawn } = require('child_process');
const { writeFileSync } = require('fs');
const readline = require('readline');
const { SpeechRecorder } = require('speech-recorder');
const { WaveFile } = require('wavefile');

let paused = true;

const ffmpeg = spawn('ffmpeg', [
 // '-f', 's16', // input format
  //'-sample_rate', '16000',
  '-i', '-', // input source
  '-c:a', 'libvorbis', // audio codec  
  'output.ogg', // output file  
  '-y'
]);

let buffer = [];
const recorder = new SpeechRecorder({
  onAudio: ({ audio, speech }) => {
    //if(speech) {

      for (let i = 0; i < audio.length; i++) {
        buffer.push(audio[i]);
      }

      if(buffer.length >= 16000 * 5) { 
        console.log('piping to ffmpeg for output');
        let wav = new WaveFile()
        wav.fromScratch(1,16000,"16",buffer);
        //writeFileSync('output.wav',wav.toBuffer());
        ffmpeg.stdin.pipe(buffer, {end: false});
      }
    //}
  }
});

// listen for keypress events
readline.emitKeypressEvents(process.stdin);
process.stdin.setRawMode(true);

process.stdin.on('keypress', (str, key) => {
  if (key.name === 's') {
    // pause or resume recording
    paused = !paused;
    if(paused) { recorder.stop(); } else { recorder.start(); }

   
  } else if (key.ctrl && key.name === 'c') {
    // exit program
    ffmpeg.kill('SIGINT');    
    process.exit();
  }
});