Batch Convert Video to MP3 on Ubuntu with FFmpeg

If you haven’t installed FFmpeg on your Ubuntu machine yet, you can do so easily via the terminal:

sudo apt update
sudo apt install ffmpeg

Here is how to create a script to batch convert video files (MKV, MP4, AVI) to MP3.

1. Create the Script “convert_to_mp3.sh”

Navigate to the directory containing your video files. Create a file named convert_to_mp3.sh using your preferred text editor (like nano or vim) and paste the following code:

#!/bin/bash
for f in *.mkv *.mp4 *.avi; do
    # Check if file exists to avoid errors if no files match an extension
    [ -f "$f" ] || continue 
    
    ffmpeg -i "$f" -vn -ab 192k "${f%.*}.mp3"
done
echo "Conversion complete."

Understanding the Script:

• for f in *.mkv *.mp4 *.avi; do: This loop iterates over all files in the current directory that match the specified extensions.
• "$f": Represents the current input file being processed.
• -vn: Tells FFmpeg to ignore the video stream and extract only the audio.
• **-ab 192k**: Sets the audio bitrate to 192 kbps (you can also use -b:a 192k).
• **"${f%.*}.mp3"**: This is the Linux equivalent of Windows’ %%~nf. It performs string manipulation to remove the original file extension so the output is named filename.mp3 instead of filename.mp4.mp3.

The empty-glob gotcha

If the folder has no .avi files, the shell doesn’t quietly skip *.avi — it hands the loop the literal string *.avi. That’s exactly what [ -f "$f" ] || continue guards against: it checks the item is a real file before passing it to ffmpeg. A cleaner alternative is to tell the shell to expand non-matching globs to nothing:

#!/bin/bash
shopt -s nullglob
for f in *.mkv *.mp4 *.avi; do
    ffmpeg -i "$f" -vn -ab 192k "${f%.*}.mp3"
done

Either way, the quotes around "$f" matter — drop them and any filename with a space breaks the command.

2. Make Executable and Run

Unlike Windows, Linux requires you to explicitly grant “execute” permissions to a script before running it.

Open your terminal in the directory and run these commands:

# 1. Grant execution permission (only needed once)
chmod +x convert_to_mp3.sh

# 2. Run the script
./convert_to_mp3.sh

The script will now process every video file in the folder and generate a corresponding MP3 file.

This re-encodes each file’s audio to MP3. For the single-file command and the bitrate/VBR options behind -ab, see converting WAV or MP4 to MP3; to cut length rather than convert, see batch trimming MP3s.