How do you convert an entire directory with ffmpeg?

Question

For Linux and macOS this can be done in one line, using parameter expansion to change the filename extension of the output file:

for i in *.avi; do ffmpeg -i "$i" "${i%.*}.mp4"; done

Previous answer will only create 1 output file called out.mov. To make a separate output file for each old movie, try this.

for i in *.avi;
  do name=`echo "$i" | cut -d'.' -f1`
  echo "$name"
  ffmpeg -i "$i" "${name}.mov"
done

And on Windows:

FOR /F "tokens=*" %G IN ('dir /b *.flac') DO ffmpeg -i "%G" -acodec mp3 "%~nG.mp3"

For Windows:

Here I'm Converting all the (.mp4) files to (.mp3) files.
Just open cmd, goto the desired folder and type the command.

Shortcut: (optional)
1. Goto the folder where your (.mp4) files are present
2. Press Shift and Left click and Choose "Open PowerShell Window Here"
or "Open Command Prompt Window Here"
3. Type "cmd" [NOTE: Skip this step if it directly opens cmd instead of PowerShell]
4. Run the command

for %i in (*.mp4) do ffmpeg -i "%i" "%~ni.mp3"

If you want to put this into a batch file on Windows 10, you need to use %%i.

A one-line bash script would be easy to do - replace *.avi with your filetype:

for i in *.avi; do ffmpeg -i "$i" -qscale 0 "$(basename "$i" .avi)".mov  ; done

To convert with subdirectories use e.g.

find . -exec ffmpeg -i {} {}.mp3 \;