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• Node.js asynchronous video conversion slow

  9 décembre 2016, par lukstei

  I wrote a little website/service, which can download a video from a website (currently Youtube) and converts it on the fly to an mp3 file and sends this file back as the response.

  For example, you when you request http://localhost:8000/v=http ://www.youtube.com/watch?v=HhoewflkQu0, then it will download this video and response the audio layer encoded in MP3.

  This all works very well, my problem is that this is very slow and I can’t figure out why.

  ---

  Simplified the script behaves like this :

  Download the video and write it to the stdin of ffmpeg, and the stdout goes to the response.
  Video (MP4, FLV) -> FFMPEG -> MP3

  I used curl to figure out how fast the script is :

  $ curl http://localhost:8000/v=http://www.youtube.com/watch?v=HhoewflkQu0

  I get only about 5-10k.

  So why is this so slow ?

  1. The server, from which I am downloading the video is slow.
  2. The conversion is slow (because of a slow CPU).
  3. The data transfer between node.js -> FFMPEG is slow.

  I tried to download the video in a normal download manager, and i got about 320k, which is my normal download speed, so the first point isn’t the bottleneck.

  To point 2 and 3, I tried to write a local file to the stdin, and I got about 600k so that isn’t it either.

  So why is my script so slow, and what can I do to make it faster ?

  https://gist.github.com/1304637

  Thanks in advance.

• When using subprocess passthrough is not accepting both inputs

  30 janvier 2021, par Baraque Obahamas

  Im trying to have two subprocesses pipe into one and output via the passthrough. My goal is to make it possible to download 2 files (one video and one audio) and combine them with ffmpeg.

  


  header('Content-Description: File Transfer');
header('Cache-Control: must-revalidate');
header('Pragma: public');
header("Content-Disposition: attachment; filename=\"ok.mp4\"");
header("Content-Type: application/octet-stream");

$cmd = "<(youtube-dl -f bestvideo[ext=mp4] --no-part --no-cache-dir --no-warnings --no-progress -o - https://www.youtube.com/watch?v=6Dh-RL__uN4) <(youtube-dl -f bestaudio[ext=m4a] --no-part --no-cache-dir --no-warnings --no-progress -o - https://www.youtube.com/watch?v=6Dh-RL__uN4) | ffmpeg -i - -i pipe:3 -movflags frag_keyframe+empty_moov+faststart -frag_duration 3600 -c:v copy -c:a copy -f mp4 -";

$cmd = passthru($cmd, $status);


  


  My error is : -bash : /dev/fd/63 : Permission denied

  


• Compression of a video with constant background

  28 juin 2017, par Spirou003

  (sorry if my english is bad, I can read it but I don’t write it quite well...)

  I want to compress some videos, which have two particularities :

  • there is a background that covers 90% of the area, during the whole video
  • most of the others elements can be separately described by a picture in move

  My videos are like this one, and don’t have audio. As you can see, almost everything can be described only by using a fixed background, few small images in move, plus a noise. Moreover, this noise will be almost nul and then an entropic coding would be very efficient. I think it will produce tiny files (< 5 Mo) even if the duration is in hours, a result that is very appreciable since I have actually recorded 30h of game (actual size is 3 Go).

  Is there any way to get new video files, that benefit of these informations ? If yes, what are the implication of a such encoding for watching these videos with Windows Media Player, or for usage with ffmpeg ?

  I searched with Google after anything that can help me, but I don’t know which keyword I can use for this, then I didn’t found anything usefull :-(

  Thanks in advance :-)

  PS : another example, the video is accelerated but shows the interesting moves