A lot of people these days are wondering which high-efficiency AAC codec they should use: aac, aac-lc, HE-AAC, or HE-AAC v2. Let’s talk about all the different specifications and their advantages and disadvantages. There is currently no “best” option, as it all depends on what you want to achieve with your encoding.
Before we continue, you can check out other similar audio codec comparisons here:
What is AAC?
AAC is an audio compression standard developed by the Motion Picture Experts Group (MPEG) organization.
The AAC allows for a more excellent dynamic range when compared to the popular MP3 digital audio format. This means it can represent both low-level and high-level sounds in much more accurate detail.
What is AAC-LC?
AAC-LC is popular among developers building mobile apps. This is because it can be played back inside iOS applications without having to license patent pools that include HEVC or HEIF decode capability.
With this licensing constraint removed from the equation, all Apple platforms including macOS and tvOS can plain playback AAC-LC content.
One of the key features of AAC-LC is that it can be encoded at all sampling rates up to 96 kHz. This means that if you pass your audio into an encoder at 48 kHz, then there’s no reason why it should only output the first half of the content.
What is HE-AAC?
HE-AAC (High-Efficiency Advanced Audio Coding) is a MPEG audio coding standard that offers better audio quality at a lower bitrate. It has for instance been chosen by the 3GPP as its mandatory audio codec in Release 6 of its specifications.
3GPP adopted the MPEG-4 Audio Lossless Coding (ALS) standard also referred to as “High-Efficiency Advanced Audio Coding” (HE-AAC).
What is HE-AAC v2?
HE-AAC v2 specifically is an improved variation on HE-AAC v1 which specifies stereophonic sound and more efficient coding among other things.
The name “v2” was chosen because it follows MPEG’s previous naming conventions for profiles of their codecs, adding a letter at the end of the original version number each time a new profile is added.
Why Use AAC?
There are many reasons to consider or use an AAC device. These devices may be used by people who have limited speech abilities due to physical, cognitive, neurological, or developmental disabilities.
Why Use AAC-LC?
AAC-LC (Advanced Audio Coding – Low Complexity) is the file format (also known as codec) used in Apple’s iPhone and iPod products when playing back AAC files. Its successor, HE-AAC (High-Efficiency Advanced Audio Coding), has fewer data compression artifacts due to its improved psychoacoustic model.
Still, this quality improvement comes at a cost, it requires more processing power to encode than AAC-LC.
For example, an audio CD encoded using the AAC-LC algorithm can be converted into a MPEG-4/AAC file that occupies about half the space of the original audio CD with little or no loss in audio quality after conversion.
The same task processed with HE-AAC takes about twice the space of the original audio CD with a near-lossless conversion rate.
In short, use AAC-LC for maximum compatibility across iPod and iPhone devices, but opt for HE-AAC where storage space is at a premium, or you don’t mind taking a slight quality hit to save a few KBs.
This includes browsers running on one’s computer and other devices which support playback of HE-AAC encoded files such as Windows Media Player.
Why Use HE-AAC?
HE-AAC has been adopted across streaming audio, fixed, and mobile applications thanks to its high quality at low bitrates, simplicity of integration, and the availability of royalty-free licensing.
Although HE-AAC can be used in conventional stereo applications, its use with 5.1 multichannel audio enables broadcasters to transition from existing standards (e.g., AC3) to a more modern technology that offers greater functionality combined with improved perceptual performance.
Why use HE-AAC v2?
HEVC enables a generation of mobile devices with a superior user experience. Audio is a critical component of the enhanced video and television experience. Therefore, HEVC must provide efficient compression for both video and audio content.
Thus, High-Efficiency AAC (AAC+) has been adopted as one of the audio coding tools within the HEVC standard, facilitating an advanced audio coding solution for broadcasters and device manufacturers alike.
This is to ensure they deliver immersive high-fidelity audio services over wireless broadband networks.
Pros of AAC
- Language boards are non-invasive, cheap, simple to make, portable, easy to update/change, and can be done at home.
- The symbols used on language boards are often very simple, making identification easy for everyone involved in a child’s life (parents, teachers, etc.)
- Children who use language boards have better opportunities for learning. This is due to increased engagement during instruction time and increased socialization because they can speak more efficiently without the need for an intermediary.
- Language boards can be used to communicate at all times, not just during school hours or when having a conversation is convenient.
Con of AAC
- AAC can be difficult to learn
Pros of AAC-LC
- Sound quality – The main advantage of AAC is that it can compress files into a smaller size than MP3.
- File sizes and streaming performance
- More efficient compression – AAC can achieve better compression efficiency at low bitrates than competing technologies – notably lossy MP3 formats.
Cons of AAC-LC
- Lack of high-fidelity sounds
Pros of HE-AAC
- High-quality sound at low bitrates: Hear the difference with HE-AAC and get your music sounding better than ever before.
- Unmatched interoperability: No matter what device you’re using, if it plays MP3s, it’ll play yours too-every time.
- Durable against degradation over time: Unlike other lossy formats, HLS audio files will stay pristine even after years of continuous listening.
- The value of a dollar: Spending a little more for a higher quality format means that your content will continue to be heard loud and clear, even after you’re gone.
Cons of HE-AAC
- Older audio players don’t support it
- It is not fully supported by all browsers that support H.264
Pros of HE-AAC v2
- One of the formats available for lossy compression
- Explicitly designed to make surround sound audio more minor. This is helpful as the internet has made sending high-quality video and audio more accessible than ever before. To save costs and prevent buffering, it’s essential that not too much data needs to be sent.
- A codec designed for streaming and sounds better than MP3 at low bitrates, making it particularly useful for low-quality internet streams such as Internet Radio
- HE-AAC v2 also provides additional features such as metadata information, including song name and artist, multi-channel output modes, etc.
Cons of HE-AAC v2
- Due to its inclusion in the MPEG-4 Part 3 standard, many patents are involved, and licensing fees may have to be paid for its use.
- Because the encoding process involves a lot more algorithms compared with traditional codecs such as AAC and MP3, dedicated hardware is required, and current mobile phones/handheld devices with multiple functions will not be able to do the encoding.
A comprehensive explanation of AAC Bitrates
The native bitrate of AAC is 128kbps though typically, the encoder will work at 64, 96, 128, or 192 kbps.
While it can be set to higher values like 240 (for 5.1 surround sound), the encoder often falls back to one of these standard rates.
The choice of quality setting has a more significant effect on the resulting file size that chooses bitrate. Using variable bit rate encoding usually results in files about 10% smaller than constant bit rate encoding with the same average bitrate.
When compressing multichannel audio, it’s possible to get better quality by using joint stereo for frequencies above 44100Hz. This is while keeping lower frequencies in stereo where they are less affected by artifacts due to the matrix.
What is AAC-LC Bitrate?
AAC-LC has an excellent overall quality compared to other audio codecs at lower bitrates but falls behind in three areas: transparency, stereo image quality, and encoding speed.
The low encoding rate means that it only produces good results at bitrates up to 320kb/s (roughly equivalent to CD quality).
Due to this limitation, AAC-LC’s usage is mainly limited to internet streaming services like Pandora and Spotify, where the music can be encoded at 96kb/s or less. It usually achieves this by applying some psychoacoustic compression.
What is HE-AAC Bitrate
The ITU standardized a codec under its standard’s name of “High-Efficiency Advanced Audio Coding” (HE-AAC). The original version was standardized in 2004, and improved versions were standardized in 2006 and 2010. These newer versions are HE-AAC v1, HE-AAC v2, and HE-AAC v3.
The three versions’ basic encoding techniques used to compress audio are very similar, but they differ in available bitrates and audio quality.
What is HE-AAC v2 Bitrate?
From my findings, it seems that most modern-day encoders use 128 kbps for AAC and 48 kbps for HE-AAC v2 when encoding song files. While these are the most common rates, there are certainly exceptions.
For example, Kanye West’s “Diamonds” is only encoded at 96 kbps in AAC format, while other artists encode their songs at higher bitrates (up to 320 kbps).
Two examples of high-quality encoding are The XX’s song “Angels,” which is encoded at 320 kbps in AAC, and Florence and the Machine’s song “No Light, No Light” encoded at 448 kbps HE-AAC v2.
Which One is Better?
There are many audio formats that you can choose from when encoding music for digital distribution. The two most popular lossy compression schemes at this point seem to be AAC-LC and MPEG-4 HE-AAC.
AAC, AAC-LC, and HE-AAC should be good enough for use in podcasts. The differences can be expected to be minor, if perceivable at all. AAC has the best encoding efficiency while requiring the least processing power to encode or decode.
Norvan Martin is the founder of BoomSpeaker.com. He is a professional Electronics Engineer and is passionate about home theater systems and AV electronics. BoomSpeaker was created as an online hub to share his knowledge and experiences as it relates to home theaters and home audio electronics.