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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.

• encoding a video for looping ?

  24 janvier 2013, par bennettk

  This is somewhat related to Looping a video with AVFoundation AVPlayer but that question is answered. What I'm trying to achieve is seamless looping using an AVPlayer. There is a noticeable stutter between loops using h264-encoded videos* that has gotten worse for some reason with the update to iOS 5. Could this have something to do with the way the videos are encoded rather than the AVPlayer ? The looping is triggered by a playerItemDidReachEnd notification as described in the link above.

  Thanks.

  * here's the ffmpeg command we're using to encode the videos, if that helps :

  ffmpeg -i -y -sameq -vcodec libx264 -vpre hq -crf 20 -an

  (yes, the files don't have sound (yet) so the -an is intentional.)

• how to improve the quality of resultant video when merging audio-video with ffmpeg ?

  6 novembre 2015, par R.S

  When merging an audio and video with ffmpeg, the quality of the resultant video goes down. How to we improve the quality(esp. the audio quality) ?

  The audio quality gets degraded to quite an extent with random screeches in between.
  I’ve tried converting the audio to mp3 and video to mp4 before merging them, tried various audio-video parameters like bitrate, sample-rate, qscale etc but still unsuccessful.
  Any help would be greatly appreciated !