ffmpeg tutorials

1. Introduction
2. Installation
- 2.1. CentOS 8
3. Live streaming with ffmpeg
4. Record audio with ffmpeg
5. Screen recording with ffmpeg
6. Concatenate multiple files
7. Merge video with audio and keeping the shortest duration (from video)
8. You can also split video.
9. You can also reduce file size drastically using this command.
10. Reduce the size of all the videos in a directory.
11. Recursively go inside directories and execute a command on them

1 Introduction

ffmpeg is a great piece of software. It is a cross platform utility to modify audio and video. It can do lot of wonderful things like editing videos, encoding them and live streaming as well. In this post I want to share whatever little I know and have been exploring.

Installing it is easy. Just check your package manager but on Arch linux you can do sudo pacman -S ffmpeg and it should install it.

2 Installation

2.1 CentOS 8

sudo rpm --import http://li.nux.ro/download/nux/RPM-GPG-KEY-nux.ro
sudo rpm -Uvh http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-1.el7.nux.noarch.rpm
sudo yum repolist
sudo dnf install ffmpeg
sudo yum-config-manager --enable powertools

3 Live streaming with ffmpeg

I recently made a video explain how to use ffmpeg to live stream from local computer to YouTube using nothing but shell scripts. Check the video here.

4 Record audio with ffmpeg

Check this link.

First check your audio devices.

arecord -l

5 Screen recording with ffmpeg

ffmpeg   -video_size 1368x768   -framerate 25   -f x11grab   -i :0.0+0,30   -f pulse   -i default   -ac 2   rec-01.mp4

6 Concatenate multiple files

6.1 Create file.txt for the concatenate to work

for f in *.mp3 ; do echo "file '${f}'" >> file.txt; done;

6.2 While concatenating multiple videos remove audio using

ffmpeg -safe 0 -f concat -i file.txt -vcodec copy -an output.MOV

6.3 Concatenate audio files

ffmpeg -safe 0 -f concat -i file.txt -acodec copy all.mp3

7 Merge video with audio and keeping the shortest duration (from video)

ffmpeg -i output.MOV -i ~/Documents/sounds_youtube/tmp/all.mp3 -map 0:v -map 1:a -filter:a "volume=0.2" -vcodec copy -shortest final.MOV

8 You can also split video.

ffmpeg -i output.MOV -ss 00:00:00 -t 00:09:00 -c copy final.MOV

9 You can also reduce file size drastically using this command.

ffmpeg -i input.mp4 -vcodec libx265 -crf 28 output.mp4

10 Reduce the size of all the videos in a directory.

for f in *.MP4;do ffmpeg -i "${f}" -vcodec libx265 -crf 28 "small_${f}";done;

11 Recursively go inside directories and execute a command on them

find . -type f -exec echo "'{}' and '{}_small'" \;