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• node.js ffmpeg spawn child_process unexpected data output

  5 septembre 2021, par PLNR

  
I'm rather new to backend stuff, so please excuse, if my question is trivial.
  
For an Intranet project, I want to present a video element in a webpage (React, HLS.js Player).
  
The video sources are mpeg-ts streams delivered as udp multicast.
  
A small node.js / express server should handle the ffmpeg commands, to transcode the multicast to hls to display them in a browser.
  

  
Problem is the Output :
  
The output is emitted on stderr... even the process is working as expected.
  
Here is the respective code I wrote for transcoding so far :

  


  const express = require("express");
const { spawn, exec } = require("child_process");
const process = require("process")

let ls;

const app = express();

app.get('/cam/:source', (body) => {
    const cam = body.params.source;
    console.log(cam);

    let source = "udp://239.1.1.1:4444";
    let stream = "/var/www/html/streams/tmp/cam1.m3u8"


    stream = spawn("ffmpeg", ["-re", "-i", source, "-c:v", "libx264", "-crf", "21", "-preset", "veryfast", "-c:a", "aac", "-b:a", "128k", "-ac", "2", "-f", "hls", "-hls_list_size", "5", "-hls_flags", "delete_segments", stream], {detached: true});

    stream.stdout.on("data", data => {
        console.log(`stdout: ${data}`);
    });

    stream.stderr.on("data", data => {
        console.log(`stderr: ${data}`);
    });

    stream.on("error", error => {
        console.log(`error: ${error.message}`);
    });

    stream.on("close", code => {
        console.log(`child process exited with code ${code}`);
    });
})

app.listen(5000, ()=> {
    console.log('Listening');
})


  


  This is maybe only cosmetics, but it makes me wondering.
  
Here is the terminal output :

  


  [nodemon] starting `node server.js`
Listening
camera stream reloaded
stderr: ffmpeg version 4.3.2-0+deb11u1ubuntu1 Copyright (c) 2000-2021 the FFmpeg developers
  built with gcc 10 (Ubuntu 10.2.1-20ubuntu1)

  --shortend--


pid:  4206
stderr: frame=    8 fps=0.0 q=0.0 size=N/A time=00:00:00.46 bitrate=N/A speed=0.931x    
pid:  4206
stderr: frame=   21 fps= 21 q=26.0 size=N/A time=00:00:00.96 bitrate=N/A speed=0.95x    
pid:  4206
stderr: frame=   33 fps= 22 q=26.0 size=N/A time=00:00:01.49 bitrate=N/A speed=0.982x    
pid:  4206
stderr: frame=   46 fps= 23 q=26.0 size=N/A time=00:00:02.00 bitrate=N/A speed=0.989x    
pid:  4206
stderr: frame=   58 fps= 23 q=26.0 size=N/A time=00:00:02.49 bitrate=N/A speed=0.986x    
pid:  4206


  


  and so on...
  

  
Any helpful information would be highly appreciated !
  
Many thanks in advance

  


• How can I create a side-by-side horizontally stacked video with a delay in video and audio using ffmpeg-python ?

  3 septembre 2021, par kup

  I am trying to create a video from two videos that will be stacked horizontally, but the resulting video is not what I expected. The same video is appearing on both sides (left and right). How can that be achieved ?

  


  The ffmpeg command I tried, which kind of worked :

  


  ffmpeg -i left.mp4 -i right.mp4 -filter_complex "
[0:v]setpts=PTS-STARTPTS[l];
[1:v]setpts=PTS-STARTPTS,tpad=start_duration=14:start_mode=add:color=black[r];
[l][r]hstack=inputs=2[stacked]; [0:a][1:a]amix=inputs=2[a]
" -map "[stacked]" -map "[a]" -c:a aac -preset superfast result.mp4


  


  The ffmpeg-python script that's not working :

  


  in0 = ffmpeg.input('0.mp4')
in1 = ffmpeg.input('right.mkv')
aout = ffmpeg.filter([in0.audio, in1.audio.filter('adelay', "5000|5000")],'amix')
vout = ffmpeg.filter([inv0.video, inv1.video.filter('tpad', start_duration=5, start_mode='add', color='black')], 'hstack')

(
    ffmpeg
    .concat(vout, aout, v=1, a=1)
    .output("out.mkv")
    .run()
)


  


  This script is not resulting in the expected output which is two videos side-by-side horizontally stacked.

  


• How can I stream a video from localhost to web browser using the video tag ?

  3 septembre 2021, par kup

  Basically what I want to stream a video to my browser both on localhost, using Flask, OpenCV, or FFmpeg.

  


  But I am not sure how to do it.

  


  I tried this :

  


  #!/usr/bin/env python
from flask import Flask, render_template, Response
import cv2
import sys
import numpy

app = Flask(__name__)

def get_frame():
    c=cv2.VideoCapture("output.mkv")

    while True:
        retval, im = c.read()
        imgencode=cv2.imencode('.jpg',im)[1]
        stringData=imgencode.tostring()
        yield (b'--frame\r\n'
            b'Content-Type: text/plain\r\n\r\n'+stringData+b'\r\n')

    del(c)

@app.route('/vid')
def vid():
     return Response(get_frame(),mimetype='multipart/x-mixed-replace; boundary=frame')


if __name__ == '__main__':
    app.run(host='localhost',port=5000, debug=True, threaded=True)


  


  But it's not working. Maybe because it is sending images. How can I stream video ?