What Is MP4? The Difference Between MP3 and MP4

MP4 files are just a newer and better version of MP3 files, right?

Well, no.

That single-digit difference might give the impression that they are more-or-less the same thing, but nothing could be farther from the truth. They each have distinct uses, histories, and advantages; MP3 and MP4 are not two editions of the same thing.

In this article, we’ll explain some of the key differences that everyone should know about. By the time you’ve finished reading, you’ll know exactly which file type is right for your needs.

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Understanding MPEG

But before we dive into the differences, it’s important to understand where the two file types originated.

MP3 is short for MPEG-1 Audio Layer 3. It was one of two formats that were considered for the MPEG audio standard back in the early-1990s. Electronics firm Philips, French research institute CCETT, and Germany’s Institute for Broadcast Technology backed the format thanks to its simplicity, lack of errors, and computational efficiency.

The decision was reached in 1991, and MP3 files entered the public domain in 1993.

MP4 stands for MPEG-4 Part 14. This technology is based on Apple’s QuickTime MOV format but adds support for various other MPEG features. The file type was first released in 2001, but it’s the 2003 re-release that’s now commonly used when you see MP4 files. There have been no further updates to the format since 2003.

Audio-Only vs. Digital Multimedia

The most fundamental difference between MP3 and MP4 is the type of data they store.

MP3 files can only be used for audio, whereas MP4 files can store audio, video, still images, subtitles, and text. In technical terms, MP3 is an “audio coding” format while MP4 is a “digital multimedia container” format.

MP3: The King of Audio

Because they are so good at storing audio, MP3 files have become the de facto standard audio format for music software, digital audio players, and music streaming sites. No matter which operating system or device you own, you can be confident MP3s will work right out of the box without a hitch. It’s why MP3 players might still be worth buying.

The main reason they’re so popular is the way the file type works. MP3s use lossy compression, which vastly reduces the size of an audio file while barely affecting its quality. The process works by stripping out all the data beyond the average person’s hearing range, then compressing the rest as efficiently as possible.

MP3s also allows users to balance the trade-off between audio quality and file size. If you’re an audiophile, you can opt for larger file sizes with higher bitrates and better audio quality. On the other hand, if you want to squeeze as much music as possible onto your portable device, you can reduce the file size and audio quality accordingly.

Furthermore, MP3s will always be smaller than equivalent MP4 files. So, if your audio player or smartphone is getting full, you should convert any audio saved as MP4 into MP3 format. Note that you may take a hit to audio quality in the process!

MP4: More Uses, More Flexibility

MP4 files are “containers”—instead of storing the code for the file, they store the data. As such, MP4 files do not have a native way of handling the coding of the file. To determine how the coding and compression will be handled, they rely on specific codecs.

There are hundreds of codecs out there today, but not many will work with mainstream MP4 players. In order for a player to be able to read and play an MP4 file, it must have the same codec itself. The most widely-supported codecs are:

• Video—MPEG-4 Part 10 (H.264) and MPEG-4 Part 2.
• Audio—AAC, ALS, SLS, TTSI, MP3, and ALAC.
• Subtitles—MPEG-4 Timed Text.

These codecs give MP4s a lot more flexibility than MP3. For example, M4A files (which are MP4 files that only contain audio) can handle both Advanced Audio Coding (AAC) and Apple Lossless Audio Coding (ALAC). The choice of quality resides with the user. Either way, the file will appear as an MP4 file, but the data within the file will differ vastly.

Besides audio, MP4 files can also contain video, images, and text. You’ll often see various file extensions that give an indication of the type of data within the container. Here are some of the most common:

• MP4—The only official extension.
• M4A—Non-protected audio.
• M4P—Audio encrypted by FairPlay Digital Rights Management.
• M4B—Audiobooks and podcasts.
• M4V—MPEG-4 Visual bitstreams.

Understanding File Metadata

Both MP3 and MP4 files support metadata. Without it, it would be impossible to effectively use music player apps (like iTunes) or home media servers (like Plex).

MP3 files use ID3 tags. They allow information such as song title, artist, album, track number, and even album artwork to be stored within the file itself. The tags are saved at the end of the file’s code—their content is either extracted by decoders or ignored as junk non-MP3 data. You can edit these tags using the popular Mp3tag.

Other pertinent information, such as ReplayGain data or DRM restrictions, can also be saved within the metadata.

MP4 files can implement metadata in the same way as MP3s, but they also introduce the Extensible Metadata Platform (XMP). XMP metadata is well-suited for MP4’s container format thanks to its compatibility with a vast number of file types, including PDF, JPEG, GIF, PNG, HTML, TIFF, Adobe Illustrator, PSD, WAV, and PostScript.

MP3 and MP4 in a Nutshell

We’ve tried to give you a balanced insight into the two file types without being too technical, and we hope you’ve now got a clearer understanding of the two formats.

In summary, if you’re saving audio for use on portable players, you should look to MP3. If you want to save video, or you want to stream your content over the internet, you should use MP4. MP4 does work for audio files, but it is not the most optimal solution.

Image Credit: Antonio Guillem via Shutterstock

Originally written by Mike Fagan on December 8, 2009