Stop making crappy MP3s with Audacity and LAME! I tell you how to encode MP3s the way LAME was designed to, so you get a great audio quality and small file size. I get a little more technical and use a lot of numbers and abbreviations, so hold on, but I hope it’s worth it.
Not for podcasts!
Since recording this episode, I discovered problems with podcasts using the below method. This is still the preferred method for music, but may produce incompatible podcast files. Instead, I recommend exporting to WAV and using iTunes to create you podcast MP3s.
Use the latest Audacity!
In case you don’t already have it, use the latest Audacity version, which improves a lot of things over older versions, adds better compatibility, and also made it easier to change your encoder options. Download here.
What file-compression and “codecs”?
In The Audacity to Podcast™, episode 5, I shared about compressing your audio to get a better, more evened-out sound. This time, I’m talking about compressing your files to save space but still maintain the highest quality you can.
“Codec” is short from compression/decompression. It’s the way a computer compresses an audio or video file to make it smaller and thus easier to transfer (or fit within limited hosting such as LibSyn). The two most-popular MP3 encoders are LAME and Faunhofer.
LAME and Fraunhofer are both the best MP3 encoders!
How can they both be the best? Because they’re designed to do different things. LAME is free and open-source and it’s what Audacity uses. Fraunhofer is licensed and is included with high-end software, but can be used free with iTunes. Cliff Ravenscraft once welcomed me on Podcast Answer Man #125 for us to discuss bitrates. But Cliff remains strongly opinionated against LAME since he prefers CBR, and I’ll explain that later.
Bitrates: kbps and KB
Audio bitrates are measured in kilobits per second (kbps), which are different from kilobytes (KB). There are eight bits in one byte. The default MP3 encoding setting is at the rate of 128 kbps.
Stereo vs. mono
Choose carefully whether you want to release your podcast episodes as stereo or mono. Stereo takes up double the space of an equal-quality mono file, because it has twice the tracks/channels. Please do not split your cohosts into left and right in your audio, unless you’re doing a special dramatization that requires positional audio. Even then, the best place for voices is right in the middle: mono or balanced in stereo.
In Audacity, encoding a mono file at a bitrate of 128 kbps means the second channel will get 128 kilobits per second to capture the details of its audio. But a stereo file at the same bitrate will split the 128 kbps between the left and right channels, thus equaling the quality of 64 kbps audio.
In iTunes, you get the same final quality regardless of choosing stereo or mono. If you select 128 kbps stereo, it gives both channels 64 kbps. If you chose 128 kbps on a mono file, it gives the single channel still 64 kbps.
Variable bitrate (VBR) versus constant bitrate (CBR)
When you select 128 kbps with constant bitrate (CBR), the MP3 encoder will use 128 kbps to digital “describe” the audio no matter what is happening. But if you switch to variable bitrate (VBR), which I suggest, then the encoder will work within a range to use more space when the audio is more complex or us less space when the audio is less complex.
LAME is the best VBR encoder. It was designed to encode music at a variable bitrate and it performs this better than any other popular encoder at the same quality (even Ogg Vorbis in most cases). Fraunhofer is the best CBR encoder. It was designed to encode audio at a constant bitrate and it performs this with better-sounding quality than LAME.
Quality and file size comparisons
In case my re-encoding of my sample audio distorted the comparison. Here are my original MP3s that you can download for comparison. Please note that when I recorded these and this episode, I had accidentally left my secondary mic on and near something that was generating noise, hence the hiss.
32kbps Stereo CBR (82 KB)
32kbps Mono CBR (82 KB)
64kbps Stereo CBR (164 KB)
128kbps Stereo CBR (324 KB)
128kbps Mono CBR (324 KB)
256kbps Stereo CBR (647 KB)
Quality-5 Stereo VBR (295 KB)
My recommended settings for great MP3s from LAME and Audacity
Go into the encoder options and switch to “Variable (VBR)”, set the quality to “5: 110–170 kbps,” Variable Speed to “standard,” and Channel Mode to “Joint Stereo.”
Share your thoughts and experience!
What kind of settings have you used when encoding MP3s? How has your quality or file sizes changed since using my suggestions?
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