Converting 216 Songs with Python & FFmpeg (m4a to mp3)

Last week, I was summoned to my uncle’s house to solve a very serious tech problem.

He had a pen drive full of old (the gold) songs and wanted to play them on his very old music player. The problem?
All of the songs, 216 to be exact, were in the m4a file format. And the music player immediately surrendered.

That’s when I realized:
“This is a perfect use case for Python + FFmpeg.”

Requirements

To solve this, we need just two things:

• Python — to loop through files and automate the process
• FFmpeg — to handle the actual audio conversion

Installing Python and FFmpeg

Install Python

Installing Python is straightforward. You can download it from the official site:

• https://www.python.org/downloads/
• Quick Guide: https://realpython.com/installing-python/

Make sure to check “Add Python to PATH” during installation (especially on Windows).

Install FFmpeg

FFmpeg installation can be a bit tricky on Windows.

• Windows:
  Download FFmpeg from https://ffmpeg.org/download.html
  Extract it and add the bin folder to your system PATH.
  Quick Guide: https://www.youtube.com/watch?v=eRZRXpzZfM4
• macOS (via Homebrew):

brew install ffmpeg

Confirm the Installation

Once installed, confirm everything is working.

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Check Python (Windows & macOS)

python --version

Check FFmpeg (Windows & macOS)

ffmpeg -version

If both commands return version info, you’re good to go ✅

Writing the Script

The Goal

• Read all .m4a files from a folder
• Convert them to .mp3
• Save the converted files in a different folder

How It Works

• Python scans the input folder and loops over files
• FFmpeg converts each file
• Python saves the output to another directory

With this in mind, I asked an LLM (ChatGPT works too) to generate a Python script, and here’s what I got:

import subprocess
from pathlib import Path

# -------- CONFIG --------
INPUT_DIR = Path("input_m4a")
OUTPUT_DIR = Path("output_mp3")
BITRATE = "192k"   # mp3 quality
# ------------------------

OUTPUT_DIR.mkdir(parents=True, exist_ok=True)

m4a_files = list(INPUT_DIR.glob("*.m4a"))

if not m4a_files:
    print("No .m4a files found.")
    exit(0)

for m4a_file in m4a_files:
    mp3_file = OUTPUT_DIR / (m4a_file.stem + ".mp3")

    if mp3_file.exists():
        print(f"Skipping (already exists): {mp3_file.name}")
        continue

    cmd = [
        "ffmpeg",
        "-y",                   # overwrite without asking
        "-i", str(m4a_file),    # input file
        "-vn",                  # no video
        "-ab", BITRATE,         # audio bitrate
        str(mp3_file)
    ]

    try:
        subprocess.run(
            cmd,
            stdout=subprocess.DEVNULL,
            stderr=subprocess.STDOUT,
            check=True
        )
        print(f"Converted: {m4a_file.name} → {mp3_file.name}")
    except subprocess.CalledProcessError:
        print(f"❌ Failed to convert: {m4a_file.name}")

print("✅ Conversion complete.")

Folder Structure

The script assumes the following structure:

project/
│
├── input_m4a/
│   ├── audio1.m4a
│   ├── audio2.m4a
│
├── output_mp3/
│   ├── audio1.mp3
│   ├── audio2.mp3
│
└── convert.py

• Put all .m4a files inside input_m4a
• Converted .mp3 files will appear in output_mp3

Running the Script

Open a terminal (Command Prompt or PowerShell on Windows) at the project root ( /project/ level), then run:

python convert.py

The script will start converting files one by one.

On average, each file (around 3–5 MB) took 4–5 seconds on my system.

Conclusion

This was a very fun programming task for me and I enjoy doing these things once in a while.

And yes… don’t forget to delete the original m4a files before handing the pen drive back to your uncle.