FFmpeg 101: A Beginner’s Guide to the Command Line

FFmpeg is a powerful, open‑source toolkit for working with audio and video. You can convert formats, trim clips, add subtitles, and much more — all from the command line. This guide teaches the mental model you need to read and write FFmpeg commands confidently.

Install FFmpeg

Follow the official documentation for your platform:

• macOS: Homebrew (brew install ffmpeg) or download from the website
• Windows: download binaries; add ffmpeg.exe and ffprobe.exe to PATH
• Linux: your distro’s package manager (e.g. apt install ffmpeg)

See: https://ffmpeg.org/download.html

Anatomy of a Command

An FFmpeg command reads: global options → inputs → per‑stream options → output file(s).

General pattern:

ffmpeg [global opts] -i input.ext [stream opts] output.ext

• Inputs start with -i. Input‑specific options must appear before their -i.
• Per‑stream options like -c:v or -b:a come after the input and before the output file.

Streams and Mapping

Files contain streams: video (v), audio (a), and subtitles (s). FFmpeg auto‑maps typical streams. For advanced cases, use -map to pick exactly what goes where, e.g. -map 0:v:0 -map 0:a:1.

Safe Defaults for Common Tasks

# Show basic media info via ffmpeg (quick peek)
ffmpeg -i input.mp4

# Transcode to H.264/AAC MP4 (good defaults)
ffmpeg -i input.mp4 -c:v libx264 -preset medium -crf 23 -c:a aac -b:a 128k -movflags +faststart output.mp4

# Remux (no re-encode): MP4 → MKV
ffmpeg -i input.mp4 -c copy output.mkv

# Extract audio as MP3
ffmpeg -i input.mp4 -vn -c:a libmp3lame -q:a 2 output.mp3

# Grab a thumbnail at 10s
ffmpeg -ss 00:00:10 -i input.mp4 -frames:v 1 -q:v 2 thumb.jpg

Pitfalls

• Option order matters (input options before -i, output options after).
• Overwriting files: add -y to auto‑overwrite or omit to be prompted.
• Quote filenames with spaces: "My File.mp4".

That’s it! With the model of inputs → options → outputs, you can read most FFmpeg commands at a glance.