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• FFMPEG - how to transcode input stream while cutting off first few seconds of video and audio

  25 septembre 2020, par purplepear24

  I am using ffmpeg to transcode a screen-record (x11) input stream to MP4. I would like to cut off the first 10 seconds of the stream, which is just a blank screen (this is intentional).

  


  I understand how to trim video with ffmpeg when converting from mp4 to another mp4, but i can't find any working solution for processing an input stream while accounting for delay and audio/video syncing.

  


  Here is my current code :

  


  const { spawn } = require('child_process');
const { S3Uploader } = require('./utils/upload');

const MEETING_URL = process.env.MEETING_URL || 'Not present in environment';
console.log(`[recording process] MEETING_URL: ${MEETING_URL}`);

const args = process.argv.slice(2);
const BUCKET_NAME = args[0];
console.log(`[recording process] BUCKET_NAME: ${BUCKET_NAME}`);
const BROWSER_SCREEN_WIDTH = args[1];
const BROWSER_SCREEN_HEIGHT = args[2];
const MEETING_ID = args[3];
console.log(`[recording process] BROWSER_SCREEN_WIDTH: ${BROWSER_SCREEN_WIDTH}, BROWSER_SCREEN_HEIGHT: ${BROWSER_SCREEN_HEIGHT}, TASK_NUMBER: 43`);

const VIDEO_BITRATE = 3000;
const VIDEO_FRAMERATE = 30;
const VIDEO_GOP = VIDEO_FRAMERATE * 2;
const AUDIO_BITRATE = '160k';
const AUDIO_SAMPLERATE = 44100;
const AUDIO_CHANNELS = 2
const DISPLAY = process.env.DISPLAY;

const transcodeStreamToOutput = spawn('ffmpeg',[
    '-hide_banner',
    '-loglevel', 'error',
    // disable interaction via stdin
    '-nostdin',
    // screen image size
    // '-s', `${BROWSER_SCREEN_WIDTH}x${BROWSER_SCREEN_HEIGHT}`,
    '-s', '1140x720',
    // video frame rate
    '-r', `${VIDEO_FRAMERATE}`,
    // hides the mouse cursor from the resulting video
    '-draw_mouse', '0',
    // grab the x11 display as video input
    '-f', 'x11grab',
    '-i', ':1.0+372,8',
    // '-i', `${DISPLAY}`,
    // grab pulse as audio input
    '-f', 'pulse', 
        '-ac', '2',
        '-i', 'default',
    // codec video with libx264
    '-c:v', 'libx264',
        '-pix_fmt', 'yuv420p',
        '-profile:v', 'main',
        '-preset', 'veryfast',
        '-x264opts', 'nal-hrd=cbr:no-scenecut',
        '-minrate', `${VIDEO_BITRATE}`,
        '-maxrate', `${VIDEO_BITRATE}`,
        '-g', `${VIDEO_GOP}`,
    // apply a fixed delay to the audio stream in order to synchronize it with the video stream
    '-filter_complex', 'adelay=delays=1000|1000',
    // codec audio with aac
    '-c:a', 'aac',
        '-b:a', `${AUDIO_BITRATE}`,
        '-ac', `${AUDIO_CHANNELS}`,
        '-ar', `${AUDIO_SAMPLERATE}`,
    // adjust fragmentation to prevent seeking(resolve issue: muxer does not support non seekable output)
    '-movflags', 'frag_keyframe+empty_moov+faststart',
    // set output format to mp4 and output file to stdout
    '-f', 'mp4', '-'
    ]
);

transcodeStreamToOutput.stderr.on('data', data => {
    console.log(`[transcodeStreamToOutput process] stderr: ${(new Date()).toISOString()} ffmpeg: ${data}`);
});

const timestamp = new Date();
const year = timestamp.getFullYear();
const month = timestamp.getMonth() + 1;
const day = timestamp.getDate();
const hour = timestamp.getUTCHours();
console.log(MEETING_ID);
const fileName = `${year}/${month}/${day}/${hour}/${MEETING_ID}.mp4`;
new S3Uploader(BUCKET_NAME, fileName).uploadStream(transcodeStreamToOutput.stdout);

// event handler for docker stop, not exit until upload completes
process.on('SIGTERM', (code, signal) => {
    console.log(`[recording process] exited with code ${code} and signal ${signal}(SIGTERM)`);
    process.kill(transcodeStreamToOutput.pid, 'SIGTERM');
});

// debug use - event handler for ctrl + c
process.on('SIGINT', (code, signal) => {
    console.log(`[recording process] exited with code ${code} and signal ${signal}(SIGINT)`)
    process.kill('SIGTERM');
});

process.on('exit', function(code) {
    console.log('[recording process] exit code', code);
});


  


  Any help would be greatly appreciated !

  


• How to effectly record and encode from udp stream(4K HECV) in real time with ffmpeg ?

  25 janvier 2021, par Sa Mei

  I have a serious problem about ffmpeg to solve.
My task is to record from udp stream(4K HECV) and encode it to a mxf file.
My CPU is Intel(R) Xeon(R) Gold 5122 CPU@3.60GHz
The situation of CPU when it is recording from udp stream

  


  The situation of the udp stream

  


  The ffmpeg I used from https://github.com/BtbN/FFmpeg-Builds/commit/86af523883173be93c69d1170d1f78f79dc5e9f8 .
The command I used is :
ffmpeg -y -threads 6 -i "udp ://@225.1.2.150:6150 ?overrun_nonfatal=1&fifo_size=50000000" -threads 32 -qscale:v 2 -alternate_scan 1 -f mxf "G :\4k.xmf"

  


  Now the speed is lower than 1.0x after running for a while(about 10minutes). Maybe this is due to the temperature of the cpu gradually increasing.
The picture above displays the performance of CPU when we specify threads=6 for decoding and threads=32 for encoding.
I found that the speed would be 1.0x if I just recorded it to a .hecv file. But now I want to encode the stream to a .mxf file in real time. But as you can see, if I tried to encode it in real time, the speed of decoding and encoding would always be lower than 1.0x (around 0.98x). After running this command for about 3 hours, the recording and encoding process will be stopped.

  


  How to solve it ? I expect that the speed is 1.0x by speeding up encoding or other ways.
Or anyone knows that how to record the udp stream without re-encoding to a .hecv file and meanwhile encode the .hecv file to a .mxf file ?

  


• node.js - Error : ENOENT : no such file or directory, unlink

  10 août 2020, par necroface

  I have the function below to convert a .wav file to .mp3. As you can see, before using the ffmpeg module to convert the audio file, I already check if the file exists or not, then upon conversion, I only keep the new file and delete the old one. But occasionally the console throws me the error Error: ENOENT: no such file or directory, unlink, which means that I unlink (delete) a non-existing file. I cannot understand why, because I already have an existence check even before the conversion, so it is supposed to have existed to be unlinked.

  



  module.exports.convertAndMoveElastic = async (calllog) => {
    let { start, sip_uri, direction, source, destination } = calllog;
    const VNtimezoneOffset = 7 + new Date().getTimezoneOffset() / 60;
    const startTime = new Date(start + VNtimezoneOffset * 3600000 - 60000);
    const date = startTime.getDate() < 10 ? `0${startTime.getDate().toString()}` : startTime.getDate().toString();
    const months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
    const month = months[startTime.getMonth()];
    const year = startTime.getFullYear().toString();
    sip_uri = sip_uri || (direction === 'outgoing' ? source : destination);
    const [extension, domain_name] = sip_uri.split("@");
    return new Promise(async (resolve, reject) => {
        const links = await getLinkWithElastic(calllog);
        if (!links) { return reject(); }
        let file_id, filepath;
        for (let link of links) {
            const { callid, sipCallid, uuid, record_path } = link._source;
            if (record_path) {
                let recordPathArr = record_path.split('/');
                file_id = recordPathArr[recordPathArr.length - 1].split('.')[0];
                filepath = path.resolve(base_directory, domain_name, 'archive', year, month, date, `${file_id}.wav`);
            }
            if (!file_id || !fs.existsSync(filepath)) {
                file_id = callid;
                filepath = path.resolve(base_directory, domain_name, 'archive', year, month, date, `${file_id}.wav`);
            }
            if (!file_id || !fs.existsSync(filepath)) {
                file_id = uuid;
                filepath = path.resolve(base_directory, domain_name, 'archive', year, month, date, `${file_id}.wav`);
            }
            if (fs.existsSync(filepath)) { break; }
        }
        if (!fs.existsSync(filepath)) { return reject(); }
        ffmpeg(filepath)
            .audioCodec('libmp3lame')
            .on('error', function (error) {
                reject(error);
            })
            .on('end', function () {
                resolve({ recordUrl: `${host}/record/download/${file_id}.mp3` });
                fs.unlinkSync(filepath);
            })
            .toFormat('mp3')
            .saveToFile(path.resolve(dest_directory, file_id + ".mp3"));
    });
};