How can I use ffmpeg_next?

I want to use ffmpeg_next in Manjaro Linux, but the instructions aren't clear.

The instructions are fairly clear - you just need to find the corresponding Arch (or Manjaro, they have same names for most parts) for the Debian ones.
Refer to the Debian package list and the Manjaro package list. For Manjaro, I think, simply using pacman -Ss will give you adequate results.

I did yay -S clang libavcodec-dev libavformat-dev libavutil-dev pkg-config but only clang and pkg-config got installed. Then I installed yay -S ffmpeg and when I search for libavcodec, libavformat and libavutil with pacman -Ss it said that they were installed. But then I tried to execute this example and I got the following error

error[E0463]: can't find crate for `ffmpeg_next`
 --> src/bin/test.rs:1:1
  |
1 | extern crate ffmpeg_next as ffmpeg;
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

For more information about this error, try `rustc --explain E0463`.
error: could not compile `reduce-video-size` due to previous error

Which is the same error I was getting before installing all that. So I don't know what else to do.

How do you build the example? Cargo should add the dependency to rustc invocation automatically.

I'm using cargo run --bin test.

Nevermind it was a silly mistake. I forgot to add the crate to Cargo.toml.