Is M4A Good Audio Quality?

File name extensions provide valuable indications of audio quality. So, what can one tell about the sound quality of files whose names end with the .m4a suffix, otherwise known as M4A files?

M4A is good audio quality compared to other files that use lossy compression. This file extension offers an advantageous balance between file size and sound quality. M4A files usually hold data encoded with efficient lossy codecs like AAC but also support lossless encoders like ALAC and FLAC.

Assessing and comparing audio quality is a somewhat tricky undertaking, given the subtleties and myriad variables involved. Nonetheless, the following technical facts and insights can perhaps assist anyone who has seen an M4A file and wondered about its potential quality.

M4A Is Good Audio Quality

The audio quality of M4A (MPEG-4 Audio) files is relatively high and will probably satisfy the needs of the average listener. Leaving aside confounding variables like bit rates, source audio characteristics, and subjective judgments, M4A is good quality compared to related files like MP3.

Files with the M4A (.m4a) file name extension usually hold data encoded through lossy compression using the Advanced Audio Coding (AAC) codec. AAC encoding is superior compared to its MP3 predecessor and performs lossy compression without noticeably compromising audio quality.

Though M4A files are typically associated with lossy encoding, they can also store data encoded with lossless compression codecs like Apple Lossless Audio Codec (ALAC) and Free Lossless Audio Codec (FLAC).

These lossless encoders compress audio data without losing audibly significant information, resulting in better sound quality than one usually encounters with lossy files.

Compressing data with efficient lossy and lossless encoders enables M4A files to produce good playback audio quality, even when encoded at low bit rates.  

To gain a clearer understanding of why M4A produces respectable audio quality, it is worthwhile investigating the design and functioning of .mp4a files.

What Is M4A?

M4A is a file name extension (.m4a) for sound files held in MPEG-4 Audio container format. It is one of the two principal file extensions used in native Apple container formats (all using the MPEG-4 format derived from Apple’s QuickTime). Remember that M4A is, technically speaking, a container rather than an audio file.

M4A files are generally not protected by digital rights management (DRM) encryption like other MPEG-4 Audio file extensions (such as MP4).

As noted earlier, M4A files support sophisticated lossy and lossless compression encoders. [ref2] M4A files contain a significantly higher proportion of perceptible input data, so the quality of their audio output is generally high. 

Advantages

The most significant advantage of M4A files is that they provide excellent audio quality in a small file size. Depending on the quality of the source audio, M4A files can sound comparable to uncompressed formats like WAV and AIFF.

M4A maintains reasonably impressive audio quality when encoded at bit rates as low as 128kbps.

As noted earlier, M4A files offer an advantageous quality-to-file size ratio because they benefit from the highly-efficient data compression of AAC or lossless codecs like ALAC and FLAC.

Disadvantages

A disadvantage of M4A is that the file extension is not as widely compatible as MP3. The hardware and software that play M4A include Apple programs and devices (iPods, iTunes) and Windows (for PC). Opportunities to access M4A files are also primarily limited to Apple platforms.

Another disadvantage is that M4A files are often slightly larger than lossy compressed MP3 files. Nonetheless, it is worth recalling M4A files hold considerably more source audio information relative to their size. The marginal increase in file size might be worthwhile if sound quality is the priority.

Comparing M4A Audio Quality To Other File Types

How does the quality of M4A compare to other kinds of audio files? In general, it is fair to say that the quality of M4A compares favorably to most other file types.

Here is a brief quality comparison between M4A and some of the most widely-used audio files. 

MP3

As seen above, M4A typically sounds better than MP3 (the most prevalent lossy format).

This comparison depends, however, on the codec used in the M4A file. [ref 7] M4A is a container file that can hold data encoded by various codecs, including MP3. By implication, an M4A file with MP3-encoded data should sound identical to an MP3 containing the same audio information.

M4A files containing data compressed with the AAC codec approximate the input data more accurately than MP3s. This sophisticated encoder allows M4A files to represent the original audio data streams with increased clarity and fidelity.

Listening tests show that the AAC encoder (normally used to encode M4A files) has a higher sound quality than MP3. These tests affirm M4A’s superiority to MP3 since files with the .m4a extension predominantly store and play AAC-encoded data.

[ref5] M4A files have higher audio quality than MP3s, even when encoded at a lower bit rate.  For instance, a 128kbps M4A file can sound comparable or even superior to an MP3 encoded at 320kbps!

M4A files encoded with lossless compression codecs like ALAC and FLAC also have higher audio quality than MP3s. Lossless M4A files sound superior to MP3s because they are compressed without the loss of aurally-significant audio data, and have significantly higher maximum bit rates than lossy codecs like MP3 (and AAC).

WAV And AIFF

The audio quality of M4A is slightly inferior, however, when compared to uncompressed file formats like AIFF and WAV. In contrast to M4A, uncompressed files hold unaltered input data, usually in high-fidelity linear pulse-code modulation (LPCM) file format.

Note that the difference in audio quality between M4A and uncompressed WAV and AIFF files is not dramatic. Most people would likely struggle to differentiate between these formats and M4A.

Frequently Asked Questions About M4A

To enhance one’s understanding of the M4A, here are the answers to some questions people frequently ask about this particular file extension.

What Player Can Play M4A Files?
While M4A is not as widely-compatible as MP3 files, the file extension operates on many commonly-used media players. Compatibility is unlikely to pose an insurmountable obstacle to listening to M4A files. 

Files with the .m4a extension are playable on popular Apple, Windows, and open-source media players, including:

  • iTunes,
  • Apple Music,
  • Windows Media Player,
  • VideoLAN VLC Player,
  • Adobe Audition.

In addition to these media players, M4A files are also compatible with Apple iPods and watches.

What Is The Bit Rate Of M4A

 Bit rates represent the number of bits conveyed in a specific period (usually one second) and provide an indication of a file’s audio quality. The bit rates of M4A files vary depending on the codecs used to process the data held on these files.

M4A files encoded with lossy compression codecs usually have bit rates of 128kbps to 256kbps. These bit rates correspond with the common settings for AAC (maximum 264kbps).

The bit rates of M4A files are considerably higher when data is encoded through lossless compression. M4A files containing data encoded with FLAC and ALAC codecs can have bit rates ranging from 400kbps to 1411kbps. The most frequently used bit rate of M4A container files with FLAC and ALAC codecs is 1411kbps.

This bit rate is equivalent to that found on compact discs. The impressive quality of M4A files encoded with FLAC and ALAC is due largely to the increased amounts of data these codecs process.

Conclusion

Files with the M4A (.m4a) file extension produce good audio quality, particularly considering they contain compressed data. The sound quality of M4A files is high because they support the efficient AAC lossy compression codec and lossless encoders like ALAC and FLAC.

M4A files offer audio quality that will satisfy most listeners. The files sound superior to the more widely-used MP3 (which is an analogous lossy file), even when encoded at lower bit rates.

References

 

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