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FFmpeg

Advanced command line toolkits for video editing and compression

What is FFmpeg?​

FFmpeg is an open-source collection of tools and libraries that allows users to record, convert, and stream audio and video in various formats. It has a command-line interface, which means it operates through a text-based command prompt, offering a wide range of capabilities for processing multimedia content.

The genius of FFmpeg lies in its versatility. It supports a vast array of codecs and formats, making it a go-to solution for format conversions, encoding, and even basic editing tasks like trimming and concatenating files. It's used by software developers and content creators alike for tasks ranging from simple file conversions to complex streaming solutions.

FFmpeg can be found on its official website: FFmpeg Official Website

How to Install FFmpeg​

macOS​

  • The easiest way to install FFmpeg on macOS is through Homebrew, a package manager for macOS.
  • Run brew install ffmpeg.

Linux​

  • Ubuntu: sudo apt update && sudo apt install ffmpeg.
  • Fedora: sudo dnf install ffmpeg.
  • Arch Linux: sudo pacman -S ffmpeg.

Once installed, you can verify the installation by running ffmpeg -version in your command prompt or terminal. This should display the version of FFmpeg installed on your system.

Use FFmpeg​

Converting Video to mp4 Format​

To convert a video to mp4 format, utilize the following command:

ffmpeg -i INPUT.mov -vcodec h264 -acodec aac OUTPUT.mp4

In case you want to convert all MOV files to mp4 in a directory, you can use the following batch script:

FILES="*.MOV"
for f in $FILES
do
  FILENAME=$(echo "${f}" | awk -F . '{ print $1 }')
  echo "${FILENAME}.mp4"
  ffmpeg -i $f -vcodec h264 -acodec aac "${FILENAME}.mp4"
done

Video Compression​

Firstly, navigate (cd) to the directory containing the videos to compress. Then, create a new compressed directory using mkdir compressed. Use the following script to generate compressed versions of each video into the new directory:

FILES="*.mp4"
for f in $FILES; do
  FILENAME=$(echo "$f" | awk -F . '{ print $1 }')
  echo "${FILENAME}.mp4"
  ffmpeg -i $f -vcodec h264 -crf 30 -vf scale=1280:720 "compressed/${FILENAME}.mp4"
done

Note: A higher crf value results in a higher compression effect and, consequently, lower video quality.

Resizing Video​

You can resize a video using the following command:

ffmpeg -i input.mp4 -vf scale=$w:$h output.mp4

Cropping Video​

The following command can be used to crop a video:

ffmpeg -i input.mp4 -filter:v "crop=w:h:x:y" output.mp4

Here, w and h represent the output video size, while x and y denote the top left corner of the cropping rectangle.

Trimming Video​

To trim a video, use:

ffmpeg -i input.mp4 -ss 00:05:10 -to 00:15:30 -c:v copy -c:a copy output.mp4

Here, -ss is the start time and -to is the end time of the video.

Removing Audio​

To remove the audio from a video, use:

ffmpeg -i input.mp4 -c copy -an output.mp4

Concatenating Videos​

First, create a text file video_concat.txt to list the videos to be concatenated:

file 'video1.mp4'
file 'video2.mp4'
file 'video3.mp4'

Then, concatenate all videos based on the order specified in the video_concat.txt file:

ffmpeg -f concat -i video_concat.txt -c copy concat.mp4

Change Keyframe Interval​

To change the keyframe interval (also known as GOP size) of a video, you can use the -g option with ffmpeg. The following command will change the keyframe interval to every 30 frames:

ffmpeg -i input.mp4 -map v:0 -c:v libx264 -g 30 output.mp4
  • -map v:0 maps the first video stream from the input to the output. If the input has multiple video streams, and you want to process only the first one, this is necessary.
  • -g 30 sets the keyframe interval to 30 frames. This means a keyframe will be inserted every 30 frames.

A higher keyframe interval often corresponds to a larger compression rate and smaller file size, but also a higher decoding time.