Lossy audio codecs have been around for a while now. The MP3 codec is the most popular of them all. But then there’s the more modern Advanced Audio Coding (AAC) format, which is being pushed by Apple as a superior alternative to the older MP3 format.
MP3 vs. AAC: Which One Is Better?
The difference between the two comes down to how efficiently each format can encode sound information with a given bitrate. That is, how well it manages that balance between file size and retained sound quality. In this article, we’ll explain why the tradeoffs involved in lossy audio compression matter, what makes one better than the other, and when you should choose one or the other.
There are many factors that go into the performance of a lossy format. Some of them may seem strange at first blush — like what happens to audio information that a coder decides to discard. Others, such as the bitrates you select, will be more familiar to you if you’ve spent time listening to digital music files.
But what does “better” really mean? There isn’t an objective right answer, because different formats perform differently based on their implementation, source material, and settings used. And some newer formats may offer benefits you’re not even aware of yet. If you want to understand why AAC might be the future of audio, this guide is for you.
What Are Lossy Audio Codecs?
Lossy audio codecs work by reducing the amount of data they use to store an audio track. The idea is that your ears can’t hear every detail, so those details don’t need to be stored. When you listen to a song, you might not notice a missing piece of bass or a slightly muffled treble, but that doesn’t make either sound worse. You lose a little bit of the original, and you gain a smaller file that plays back just fine.
At the simplest level, the lower the bitrate, the less data a lossy codec uses. Lower bitrates typically mean more noticeable differences in sound; higher ones usually result in near-identical playback to the original recording. It’s possible to create high-quality audio files that play back flawlessly using a variety of formats. But it’s also possible to make low-bitrate audio files that are clearly lacking.
Some formats compress data more efficiently than others. So although both AAC and MP3 are lossy, they aren’t exactly interchangeable. We’ll look at the differences later, but let’s start off with a quick summary:
Lower Bitrates: More significant differences in sound, smaller files
Higher Bitrates: Near-identical playback, small files
Sound Quality Comparisons: AAC vs. MP3
You could say that AAC is typically more efficient than MP3. On average, an AAC file encoded at 128 kbps tends to sound better than an MP3 file encoded at the same bitrate. And sometimes it can be even more efficient, especially at lower bitrates. A 64 kbps AAC file might actually sound just as good as a 96 kbps MP3 file.
That tendency exists, though, without guaranteeing that it always does. For example, Sage Audio compared 320 kbps MP3 and AAC files against a WAV original and found that, in that particular null test, the joint-stereo MP3 deleted less signal than the AAC.
In reality, the vast majority of tests show AAC encoding outperforms MP3, particularly at lower bitrates. This isn’t always true, however, and depends on how the MP3 encoder was implemented, what mode it was recorded in, what type of source material it was derived from, and which version of the MP3 standard it was following.
Both AAC and MP3 have different versions of themselves, too. Some profiles of these formats favor high-bitrate listening, while others target mobile devices. What matters is that both AAC and MP3 can become extremely similar to each other, especially as you approach the 320 kbps limit.
Modern AAC Support
Apple Music delivers its content over the internet in AAC format, rather than MP3, and the Apple ecosystem generally supports AAC. Most portable players, including the iPod Shuffle and the iPod Touch, support both AAC and MP3. Likewise, your car system, your gaming hardware, and the apps you use probably support AAC and/or MP3.
But that doesn’t necessarily mean every profile of AAC will work on every device. For instance, the AAC-LC (low complexity) format is supported by virtually every modern phone, computer, and portable player you can name. But there’s no guarantee that HE-AAC, which is designed for lower bitrates, will play on your smartphone.
AAC-LC vs. HE-AAC
AAC has several versions. AAC-LC stands for “low complexity,” which means it can be played back using minimal computing power. HE-AAC stands for “High-Efficiency AAC,” which is designed to improve efficiency and lower the overall bitrate.
HE-AAC works best in scenarios where bandwidth is limited. AAC-LC is compatible with a broad range of modern devices, but HE-AAC support can be less certain. Neither variant has MP3’s long track record of near-universal playback. If you’re unsure whether your particular platform supports the more advanced variants of AAC, opt for the common, low-complexity format instead.
AAC Use Cases
If you already own a modern smartphone, there’s little reason to avoid AAC. Modern phones and tablets typically come with ample storage space and plenty of available network bandwidth to stream large files. While both AAC and MP3 files take up roughly the same amount of space, AAC is a more efficient format than MP3. That’s great news, since you won’t need to spend much of your hard drive space storing digital music files.
Because AAC files tend to play back at lower bitrates than MP3s, they also play back faster on streaming services. That means you can begin playing songs sooner and avoid buffering, which improves your listening experience. Finally, AAC files play back very nicely with spoken content like podcasts. They’re also a common option for Apple and YouTube-oriented listeners.
Still, there are situations in which MP3 is still the format of choice. If you have questions about the specific capabilities of your particular hardware or software, it’s worth testing the waters yourself. Otherwise, feel free to assume that MP3s will work across the board.
MP3 Use Cases
When it comes to guaranteed playback, nothing beats MP3. It’s been around longer, and it continues to work well in environments you’d expect to find it, such as older, niche, unfamiliar, or mixed recipient systems. Because of the longevity of MP3, it remains the safer choice if you don’t know what you’re dealing with on the playback end.
MP3 has enjoyed broader playback-system recognition than any other audio format, and it’s been included in everything from your old walkman to your latest smartphone. It doesn’t hurt that MP3 is tied to no one operating system, either. You can easily share an MP3 file with someone who runs Linux, Windows, macOS, or Android.
It’s important to clarify the difference between a codec, a container, and the filename extension associated with them. An audio file is typically contained within another file format known as a container, which contains both metadata and the compressed audio itself. You may not be aware of this, but the name of a codec isn’t always the same thing as the filename extension you see. AAC-encoded audio can show up as .aac or .adts, and it is commonly packaged inside .mp4-related files.
In practice, it’s almost always easier to think of audio files in terms of their filename extensions. The most commonly encountered MP3 files will simply have a .mp3 extension. AAC audio, rather than MP3 audio, is what commonly appears inside .mp4 containers. AAC files will typically carry an .m4a extension, or .aac or .adts, depending on how they were encoded.
Conclusion: AAC or MP3?
AAC and MP3 both do an excellent job of compressing your favorite tunes, and neither format has an overwhelming advantage over the other. The decision largely depends on your playback environment.
If your playback chain is relatively modern, then choose AAC. Its more efficient compression can help you save space and reduce load times, which helps you get the most enjoyment from your audio library.
However, if there’s uncertainty regarding your playback setup, it’s often safer to rely on MP3. Although MP3 is generally less bitrate-efficient than AAC, it’s a tried-and-true technology that will play on virtually every system you can name.
Ultimately, you shouldn’t choose one format over the other simply because of its name. Instead, consider how well the file encodes and plays back. Always remember that what matters most is the actual player you’re going to use to listen to your music.