In one of my previous tutorials, I’ve shown you how to convert M4B to MP3 so that it improves compatibility and lets you listen to your audiobooks in any media player of your choice. In this tutorial, let me show you a simple way to convert MP3 to Opus.

While the MP3 format is pretty good, it’s an overkill for audiobooks and other interactive speech files such as text-to-speech. That’s where the Opus lossy audio codec comes into play. Opus is widely supported and used by big names like Spotify. The best thing is, the Opus format offers similar audio quality for audiobooks at a reduced file size. For example, my 196 GB audiobook library is now only 104 GB when converted to Opus. To put it simply, if you have a large MP3 audiobook library, converting it to Opus format will help in space saving.

Without further ado, let’s get started. Follow the steps in this tutorial to convert MP3 to Opus with FFmpeg.

Follow the steps given below to convert an MP3 file to Opus format using FFmpeg:

Step 1: Install FFmpeg on Windows and add it to the system path.

Step 2: Right-click on the Start icon and select Windows Terminal.

Step 3: Type ffmpeg in the command window and press Enter. You should see the ffmpeg version number. It should be v6.0 or higher.

Note: If you see an error or ‘the common is not recognized’ message then ffmpeg is not installed or added to the system path.

Step 4: Run the below command to convert an MP3 file to Opus. Replace the dummy input file path and output file name.

As soon as you run the command, ffmpeg will convert the MP3 file to Opus and saves it to the same directory using the output name you’ve given it. How much time it will take to convert the files depends on the file size, duration, and your system hardware specifications. Once that is done, you can close the terminal window.

By default, the above command encodes the opus file in 32 kbps (bit rate), which is good enough for most audiobooks. You can even reduce it down to 24 kbps. However, you can increase the bit rate to 96, 128, 256, or 450 kbps when needed. To do that, all you have to do is replace the “32k” in the command with the desired bit rate. Here’s an example command which uses 128 kbps.

Note: 256 kbps and 450 kbps are useful for 5.1 and 7.1 surround sound settings respectively.

Do keep in mind that the higher the bit rate, the higher will be the file size. If your main goal is to reduce the file size then I recommend using 32 kbps or 24 kbps.

Also, if your audiobooks have a heavy background or environmental music, like graphic audiobooks then don’t convert them to opus format. Use MP3 or M4B.

That is it. It is that simple to convert any MP3 file to Opus format. I hope this tutorial helped you in reducing your audiobook library size.

If you are stuck or need help, send an email, and I will try to help as much as possible.

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