Vladimir Cicovic Blog

This is just some cheat sheet about the FFmpeg command line. To know about the history there is link.

This tool is very good if you are in any kind of job with video or live streaming. You can convert from any format to any other format. Even some mp4 to mp3, or different format codec.

Cut from second 10 up to next 10 seconds. So from 10 to 20 seconds of video would be new 10 seconds video.

ffmpeg -ss 00:00:10.0 -i somevideo.mp4 -c copy -t 00:00:10.0 outsomevideo.mp4

You have a video in ISO Media, MP4 v2 [ISO 14496-14] and twitter does not want to play. So you need ISO Media, MP4 Base Media v1 [IS0 14496-12:2003]

ffmpeg -i input.mp4 -c copy -map 0 -brand mp41 output.mp4

To copy the video from video.mp4 and audio from music.mp4:

ffmpeg -i video.mp4 -i music.mp4 -c copy -map 0:0 -map 1:1 -shortest output.mp4

"Burn" subtitles to video. First convert .srt to .ass

ffmpeg -i somesub.srt somesub.ass

Then add them:

ffmpeg -i ourfavmovienosub.mp4 -vf ass=somesub.ass ourfavmovieswithsub.mp4

If you want to mute or silence some part of video(let say from 0:30 to 1:30:

ffmpeg -i ourfavmovies.mp4 -vcodec copy -af "volume=enable='between(t,30,90)':volume=0" outourfavmovies.mp4

Extracting pictures from video, each second:

ffmpeg -i  favmovies.mp4 -vf fps=1 pic%04d.jpg -hide_banner

I hope this helps you with video editing.

Before half-century, each bit inside of the computer was important. One of the most frequently used function was "swap".

Swap do the simple thing and you can say well I know. But in that time each operation and memory usage was important. So to have an efficient swap between 2 variables and not using third variables.

So trick goes like this:

A = A + B
B = A - B
A = A - B

Instead of:

TMP = A
A = B
B = TMP

Python code (tnx to Jovan Sh):

>>> a = 5
>>> b = 3
>>> (a, b) = (b, a)
>>> print a,b
3 5

With this approach at that time, programmers save a lot of memory usage.

Also, you can find all these tricks in the book Hacker's Delight

In one moment of web page life - there is some bottleneck. It could be not using compression, a slow DNS response, a big size of jpg or larger picture format (example Jpeg optimization tools, wrong SSL/TLS settings, or missing and similar.

Pagespeed Insights

Very handy tool working really well.

PageSpeed Insights

Pingdom Website Speed Test

This tool is different than the previous one. It shows many things and recommends + it has different locations to run the test.

Pingdom Website Speed Test

Gtmetrix

It has different tools for checking speed, how content is loaded as also giving tips to improve speed.

GTMetrix

SSLabs

Swiss knife for SSL/TLS and gives recommendations on how and what to improve SSL/TLS settings.

SSLabs