Clarification of MPEG 4, AAC and Apple

Based on posts/responses on the forums, it appears there is still a significant amount of confusion regarding audio codecs and their implications.

For clarification purposes, "MP3" is officially known as MPEG-1 Layer 3. This audio codec provides the popular compression format that both iTunes and the iPod support.

Songs can be encoded at varying "bitrates". The most common bitrate for MP3 is probably "128kbps". This translates into 128 kilobits per second -- which means the format will use 128kilobits of data to encode one second of audio - no more, no less. Therefore, the final size of a file depends on both Bitrate and the Length of the Song.

Many users, however, prefer to utilize larger bitrates to achieve higher quality audio, but at the sacrifice of a larger final file size. Based on this popularly referenced c't magazine blinded study, it is commonly held that 256kbps MP3s are equivalent to original CD Audio:


    In plain language, this means that our musically trained test listeners could reliably distinguish the poorer quality MP3s at 128 kbps quite accurately from either of the other higher-quality samples. But when deciding between 256 kbps encoded MP3s and the original CD, no difference could be determined, on average, for all the pieces. The testers took the 256 kbps samples for the CD just as often as they took the original CD samples themselves.

AAC/MPEG4

This page at Apple helps clarify some terms and definitions regarding the audio format: AAC. Advanced Audio Coding (AAC) is the audio codec for the standard known as MPEG-4. According to Apple's site, AAC provides multiple advantages over MP3 -- but the most significant for end-users is the improved compression algorithm:


    AAC compressed audio at 128 kbps (stereo) has been judged by expert listeners to be "indistinguishable" from the original uncompressed audio source.*

As a result, the advantage of AAC will be better quality audio at the same file sizes. Or, alternatively, equal or better quality at smaller sizes.

Some commonly asked questions:

Q: Is a 128kbps AAC/MPEG4 file smaller than a 128kbps MP3?

A: No. They are exactly the same size... but the AAC file should sound better. See above.

Q: Will there be a way to convert my MP3's to AAC files?

A: Converting directly from MP3 to AAC is not recommended (by this author). Going from a 128kbps MP3 to a 128kbps AAC file will provide no space spavings, and yet you will likely lose audio quality. (both are "lossy" file formats). Remember, you will never "regain" the quality lost when a song was encoded into MP3. The recommended course of action would be to re-rip the files from its original format (CD, for example).

Top Stories

First Impressions From New iPhone 12 and 12 Pro Owners

Thursday October 22, 2020 4:20 pm PDT by
It's already Friday, October 23, in Australia and New Zealand, which means some customers who purchased an iPhone 12 or 12 Pro already have their new devices in hand. We've seen dozens of reviews of the iPhone 12 and iPhone 12 Pro from media sites, but now first impressions from regular Apple customers are available. Image via MacRumors reader Boardiesboi New iPhone 12 and 12 Pro owners are...

New Photos Offer Better Look at iPhone 12 Color Options

Tuesday October 20, 2020 2:34 am PDT by
As we wait for the iPhone 12 review embargo to lift later today, more pictures are circulating of the devices in real-world lighting conditions, providing a better look at the different colors available. Leaker DuanRui has shared images on Twitter of the iPhone 12 in white, black, blue, green, and (PRODUCT)RED. The black and white colors are similar to the iPhone 11 colors, but the other...

Photographer Austin Mann Tests the iPhone 12 Pro's Camera

Wednesday October 21, 2020 4:14 am PDT by
Travel photographer Austin Mann usually performs an in-depth review of new iPhone models to test their camera performance in real-world scenarios. To test Apple's new iPhone 12 Pro, Mann traveled to Glacier National Park, Montana. Mann focused on some of the biggest camera upgrades with the iPhone 12 Pro, including the upgraded Wide lens, Ultra Wide Night mode, and LiDAR autofocus, across a...

iPhone 12 Pro Max Has Smaller 3,687 mAh Battery According to Regulatory Filing

Tuesday October 20, 2020 8:48 pm PDT by
Apple's new iPhone 12 Pro Max is equipped with a 3,687 mAh battery, which is around 7% less capacity than the 3,969 mAh battery in the iPhone 11 Pro Max, according to a regulatory filing published by TENAA, the Chinese equivalent of the FCC. The regulatory filing, spotted by MacRumors, also lists the iPhone 12 Pro Max with 6GB of RAM as seen in benchmark results last week. Apple has filed ...

5G Drains iPhone 12 Battery 20% Faster Than 4G in Benchmark

Wednesday October 21, 2020 3:17 am PDT by
After the first reviews for the iPhone 12 and iPhone 12 Pro emerged yesterday, a new report by Tom's Guide reveals the extent of battery life reductions when using 5G. The report outlines a test wherein the iPhone surfs the web continuously at 150 nits of screen brightness, launching a new site every 30 seconds until the battery drains. Interestingly, the test was run on an iPhone 12 and...

Teardown Video Confirms iPhone 12 and iPhone 12 Pro Use Same 2,815mAh Battery

Thursday October 22, 2020 9:47 am PDT by
With the iPhone 12 launching on Friday and in just a few hours to Australia and New Zealand, hands-on videos, teardowns, reviews, and other iPhone-related content has been coming out. A new teardown video delves into both the iPhone 12 and the 12 Pro, confirming battery life for both models and giving us a closer look at their internals. The video from Io Technology is in Chinese, but ...

French iPhone Boxes Come Packed in an Outer Box With Separate EarPods

Wednesday October 21, 2020 6:52 am PDT by
After the news that France would be the only territory to continue to include EarPods with the iPhone, it seems that Apple is not packing the earbuds within the iPhone's box (via iGeneration). Screenshot from TheiCollection's review video The French iPhone 12 and iPhone 12 Pro does not have a different retail box to accommodate EarPods, meaning that all iPhone boxes are consistent...

Some Defective Apple iPhone 12 Cases Shipping Without Speaker Holes

Wednesday October 21, 2020 12:54 pm PDT by
At least two customers who have purchased iPhone 12 cases have received defective cases that do not have speaker holes, which obscures the sound. Photo by Reddit user zarnold16 There have been two separate threads on Reddit from iPhone 12 customers who purchased a case and received one without speaker holes. One customer was told by an Apple advisor that the case wasn't meant to have...

Watch: New iPad Air Unboxing Videos and First Impressions

Wednesday October 21, 2020 6:00 am PDT by
Apple's embargo has lifted on reviews for the new iPad Air ahead of its launch on Friday. In addition to our more detailed review roundup, we've shared a handful of unboxing videos and first impressions of the device below. The new iPad Air via Karl Conrad The new iPad Air features a larger 10.9-inch edge-to-edge display, a faster A14 Bionic chip, and a USB-C port instead of Lightning. It is...

Apple's AirTags Revealed in Newly Published Patent Applications

Thursday October 22, 2020 9:13 am PDT by
Two patent applications filed by Apple appear to depict the company's widely expected AirTags item trackers (via Patently Apple). The filings, which include a large number of images, are titled "Mounting Base for a Wirelessly Locatable Tag" and "Fastener with a Constrained Retention Ring," and describe a wirelessly locatable tag that can be used to determine the absolute location of an...