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• Extracting subtitles of a mkv file using ffmpeg while downloading

  19 août 2020, par Tim Untersberger

  I am trying to stream a mkv file to a webpage, which is being downloaded using WebTorrent. The video file has ASS/SSA embedded subtitles. I am using electron to display the video, which uses chromium without proprietary codec support, so I have to use the following html :

  


  <video controls="controls">&#xA;  <source src="video.mkv" type="video/webm">&#xA;<video></video>&#xA;</source></video>

  


  Since chrome supports webm and they use the same container, I can watch the video with audio. Webm doesn't support embedded subtitles, so the subtitles of the video get ignored.

  


  I am extracting the subtitles using the following command :

  


  ffmpeg -i video.mkv -map 0:2 sub.vtt


  


  This works fine, but requires the file to be downloaded completely. Is it possible to extract the subtitles while the file is being downloaded, so that I can begin streaming the video together with the subtitles as soon as possible ?

  


• Alternatives to Facebook 360 Encoder for Spatial + Headlock Encoding ?

  31 juillet 2023, par Robert N

  Unfortunately FB 360 Encoder is no longer being worked on with no alternatives that I can find & right now I cannot get it to work on mac.

  


  I am looking to combine two stems as per the tutorial here - 1 spatial audio (16channel) with 1 headlock audio (stereo) for a 180 stereo (side by side) video in the highest quality allowed for a Meta Quest 2 headset.

  


  FFMPEG recipes are preferred but paid alternatives are welcome. So far the best I could find for encoding was "use the old software" but even if it worked, I do not trust out of date/dead software for production : Facebook 360 Encoder Error - FFmpeg libavdevice.57.dylib (not a mach-o file)

  


• How do I change the default path of my homebrew installation ?

  22 février 2021, par Make Perceive

  I'm using both ffmpeg and youtube-dl, installed via homebrew. Mac M1 Apple silicon. They both work fine when I run a command from Terminal, but when I try to run commands via a third party automation script, I'm getting an error and I think it's because the javascript is looking for ffmpeg in the wrong location (something like "opt/bin/youtube-dl" as opposed to "/opt/homebrew/bin/youtube-dl". In this particular example, I think it relies on ffmpeg to do the conversion even though it's using youtube-dl.

  


  I don't know what the best practice is, and in my homebrew install I did see something saying something like "next steps change eval >> path" ; I pasted the line into terminal and ran it but it does not seem to have worked.

  


  Here's an example of the javascript.

  


  
const youtubeDL = '/opt/homebrew/bin/youtube-dl';
var url = 'https://www.youtube.com/watch?v=8YUc5-XaBbI';

log(`Download started`);

var execResult = sf.system.exec({
        commandLine: `"${youtubeDL}" "${url}" --extract-audio --audio-format wav`
    });

log (execResult)

if (execResult.exitCode !== 0) {
    throw `MP4 download failed with exit code: ${execResult.exitCode}`;
}

log('MP4 downloaded');
log (youtubeDL);
log (url);




  


  The error that I'm getting says "ffprobe/avprobe and ffmpeg/avconv not found".