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• DWT of frames by FFMPEG API

  13 mars 2015, par Vaigard

  How can I spend the DWT Y component is considered of H.264 video frame ? Do not quite understand the principle of filling the structure DWTContext and its schema. And is not a matter of AVFrame->data[0][x] values are already converted, for example by DCT ?

  Thanks and sorry for my English=)

• Extract subtitle by language code via ffmpeg

  7 mai 2023, par TrustFound

  I have a simple task - extract subtitle for exact language from tvshows.
For example, I want to extract English subtitles from Netflix's show.
As you know there're a few different types of subtitles : forced, full and SDH.
So I want to extract all of them if it has eng language code.

  


  To extract 1 subtitle from file I used this code for windows :

  


  FOR %%i IN (*.mkv) DO (ffmpeg.exe -i "%%i" -map 0:s:m:language:eng -c copy "%%~ni".eng.srt)


  


  It worked fine with 1 english subtitle per file. But if it contains 2, ffmpeg shows error

  


  


  SRT supports only a single subtitles stream

  


  


  ---

  


  MI is...

  


  

  • Stream #0:2(eng) : Subtitle : subrip

  


  • Stream #0:3(eng) : Subtitle : subrip

  


  • Stream #0:4(ara) : Subtitle : subrip

  


  • ...

  


  


  ---

  


  So I should set 2 or more output files. I tried to figure out how to do this and found similar threads on reddit and stacksoverflow. They said there's no way to do this without ffprobe.
So I used ffprobe to parse all subtitle tracks and their language code.

  


  FOR %%i IN (*.mkv) DO (ffprobe -loglevel error -select_streams s -show_entries stream=index:stream_tags=language -of csv=p=0 -i %%i > subs.txt)


  


  File contains this info :

  


  

  • 2,eng

  


  • 3,eng

  


  • 4,ara

  


  • ...

  


  


  ---

  


  As I understand I should use integers and set them values 2 and 3. I want to get output like this

  


  


  

  • MovieName.2.eng.srt

  


  • MovieName.3.eng.srt

  


  


  


  If it easier to extract all subs, let it be. I tried to do this too but I dont know how to set integers and use them :(
So what I should do ?
Thanks in advance

  


• record video from website using puppeteer + ffmpeg

  8 novembre 2020, par rudolfninja

  I'm trying to record video from website using the way similar to puppeteer-recorder, but I want to stop recording by myself and then save it to file (after I stopped it). I wrote simple web service for this purpose :

  


  var express = require('express');
var app = express();
const { spawn } = require('child_process');
const puppeteer = require('puppeteer');
var record = true;


app.get('/startRecord', function (req, res)
{
const frun_record = async () => {
    console.log("Start recording");
    const browser = await puppeteer.launch();
    const page = await browser.newPage();
    await page.goto('http://worldfoodclock.com/', { waitUntil: 'networkidle2' });
    var ffmpegPath = 'ffmpeg';
    var fps = 60;

    var outFile = 'E:\\Code\\video-record\\output.webm';

    const args = ffmpegArgs(fps);

    args.push(outFile);

    const ffmpeg = spawn(ffmpegPath, args);

    const closed = new Promise((resolve, reject) => {
        ffmpeg.on('error', reject);
        ffmpeg.on('close', resolve);
    });

    console.log("Entering loop");

    while (record) {
        let screenshot = await page.screenshot({ omitBackground: true });
        await write(ffmpeg.stdin, screenshot);
    }
    ffmpeg.stdin.end();
    console.log("Recording stopped");
    await closed;
};
frun_record();
res.end( "starting recording" );
})

app.get('/stopRecord', function (req, res) {
 record = false;
 res.end( "stopped" );
})

const ffmpegArgs = fps => [
  '-y',
  '-f',
  'image2pipe',
  '-r',
  `${+fps}`,
  '-i',
  '-',
  '-c:v',
  'libvpx',
  '-auto-alt-ref',
  '0',
  '-pix_fmt',
  'yuva420p',
  '-metadata:s:v:0',
  'alpha_mode="1"'
];

const write = (stream, buffer) =>
    new Promise((resolve, reject) => {
        stream.write(buffer, error => {
            if (error) reject(error);
            else resolve();
        });
    });

var server = app.listen(8081, function () {
var host = server.address().address
var port = server.address().port
console.log("Example app listening at http://%s:%s", host, port)
})


  


  But it always record only 1 second video, looks like stream is just overwritten. I tried just save screenshots on disk and it was more than 1 second of video.
So the main question is how to put all the screenshots into the stream and then save it on disk ? And another thing I'd like to know is what the frequency of taking screenshots from web page ?