Slow down a video “mencoder”, “ffmpeg” and “sox”

Published by TheJoe on

Estimated reading time: < 1 minute


This article was published more than a year ago, there may have been developments.
Please take this into account.

Today we still talk about video editing command line, ffmpeg as well as we will see in broad terms how they work mencoder and sox: is the first part of the project “mplayer“, the second helps us in definition audio. The end result of this tutorial will be the original video (including audio) slowed. In short will last twice.

To begin with we must have a video format “mp4“. If we use our size differs ffmpeg by convertirlo.

ffmpeg -i <my_video.dvd> converted.mp4

We replace “<my_video.dvd>” with the actual name of our videos. The result will be “converted.mp4“, the video in the right format.

We can now slow il video. We will use “mencoder“.

mencoder -ovc copy -oac mp3lame -speed 0.5  converted.mp4 -o slow.mp4

Estraiamo audio with ffmpeg:

ffmpeg -vn  -i slow.mp4 slow.wav

Now we can delete the fileslow.mp4“, we will not need more.

We raise the tone the file “slow.wav” with “sox“:

sox slow.wav slow_but_pitched_up.wav pitch 1200

And now create a slowed down version of “converted.mp4” soundless:

mencoder -ovc copy -nosound -speed 0.5  converted.mp4 -o slow_no_sound.mp4

We combine video and audio with “mencoder“…

mencoder -ovc copy -audiofile slow_but_pitched_up.wav -oac faac slownosound.mp4 -o slomo.mp4

… with the ffmpeg.

ffmpeg -i slownosound.mp4 -i slow_but_pitched_up.wav -map 0.0 -map 1.0 slomo.asf

If we want to convert the video in the initial format we still use ffmpeg as in the first step.

ffmpeg -i slomo.mp4 <my_video.dvd>


I keep this blog as a hobby by 2009. I am passionate about graphic, technology, software Open Source. Among my articles will be easy to find music, and some personal thoughts, but I prefer the direct line of the blog mainly to technology. For more information contact me.


TheJoe · 9 August 2012 at 9:26 AM

QWinFF is a beautiful project, it is a gui to ffmpeg. In practice it is a graphical interface. All work is done by ffmpeg, qwinff does nothing but make things easier. Good advice.

gold account · 7 August 2012 at 6:24 AM

QWinFF also allows you to create or edit the present setting the format quality etc. that we want to convert our files.

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