......_..._..._..._......
...../ \./ \./ \./ \.....
....( L | A | M | E )....
.....\_/.\_/.\_/.\_/.....
...._..._..._..._..._....
.../ \./ \./ \./ \./ \...
..( L | E | M | O | N )..
...\_/ \_/ \_/ \_/ \_/...
.........................

Useful terminal commands and tools

Introduction

These are commands and tools that I use often but need help remembering.

Contents

ffmpeg

Capture screen as dummy video

modprobe v4l2loopback
sudo ffmpeg -video_size 1920x1080 -framerate 25 -f x11grab -i :0.0+1920,0 -vcodec rawvideo -pix_fmt yuv420p -threads 0 -f v4l2 /dev/video2

Loads the v4l2loopback module which creates a new dummy device under /dev/. You may have to include video filter hflip (i.e. -vf 'hflip'), before /dev/video2, if the video output is mirrored.
-video_size Sets the video frame size.
-f Forces the input or output file format. Here the X11 video input device and the Video4Linux2 video input device.
-i Grabs at position from top left. Here with 1920 offset, to get the second monitor.
-vcodec Uses raw video decoder for rawvideo streams.
-pixfmt Uses yuv420p colour encoding system.

Explanation:

Concatenate two video files with audio

(with the same codec)

ffmpeg -i cut.mkv -i cut_reversed.mkv -filter_complex "[0:v] [0:a] [1:v] [1:a] concat=n=2:v=1:a=1 [v] [a]" -map "[v]" -map "[a]" combined.mkv
-i Specify input filename
-filter_complex Creates a complex filtergraph with inputs and/or outputs
-map Designate one or more input streams as the source for the output file

Explanation:

Convert video to gif

ffmpeg -y -i combined.mkv -vf fps=24,scale=1080:-1:flags=lanczos,palettegen palette.png
ffmpeg  -i combined.mkv -i palette.png -filter_complex "fps=24,scale=1080:-1:flags=lanczos[x];[x][1:v]paletteuse" out.gif
-y Overwrite output without asking
-i Specify input filename
-vf Video filtergraph
-filter_complex Creates a complex filtergraph with inputs and/or outputs

Explanation and other resources:

Create webm for 4chan

ffmpeg -i your_video.mkv -ss 00:00:10.000 -to 00:00:20.000 -c:v libvpx -crf 4 -b:v 1500K -vf scale=640:-1 -ac 1 -c:a libvorbis output.webm
-ss Seek start position
-to Seek end position
-c:v Encode all video streams
-crf Constant Rate Factor, range from 0-51, lower is better quality
-b:v Set bit-rate of video output file
-vf Video filtergraph, used in this case to set width with automatic height according to ratio
-ac Set number of audio channels, in this case to 1 so we reduce file size
-c:a Encode all audio streams

Merge audio and video

Applies if video has audio

ffmpeg -i video.mkv -i audio.mp3 -c:v copy -c:a aac -strict experimental -map 0:v:0 -map 1:a:0 ouput.mkv
-i Specify input filename
-c:v Encode all video streams
-c:a Encode all audio streams
-strict Specify how strictly to follow the standards
-map Designate one or more input streams as the source for the output file

Reverse video and audio

ffmpeg -i input.mkv -vf reverse -af areverse output.mkv
-i Specify input filename
-vf Video filtergraph
-t Audio filtergraph

Trim video

ffmpeg -i input.mkv -ss 00:00:03 -t 00:00:08 -async 1 output.mkv
-i Specify input filename
-ss Seek start position
-t Duration after start position
-async 1 Start of audio stream is synchronised

Resources

tar

Create an archive

tar -cvf send.tar send/
-c Create an archive
-v Verbose
-f Specify filename

Create a gzip compressed archive

tar -czvf send.tar.gz send/
-c Create an archive
-z Compress archive with gzip
-v Verbose
-f Specify filename

Extract an archive

tar -xvf send.tar
-x Extract an archive
-v Verbose
-f Specify filename

Extract a gzip compressed tar archive

tar -xvzf send.tar
-x Extract an archive
-v Verbose
-z Decompress using gzip
-f Specify filename

List files in an archive

tar -tvf send.tar
-t List contents
-v Verbose
-f Specify filename

List files in a compressed archive

tar -tzvf send.tar.gz
-t List contents
-z Decompress using gzip
-v Verbose
-f Specify filename

Extract a specific file from an archive

tar -xvf send.tar my_taxes.xlsx scan.pdf
-x Extract an archive
-v Verbose
-f Specify filename

:)