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How AAC works

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How AAC works

AAC Music File Format

Like MP3, AAC is a lossy music storage format. As in the case of the MP3 format, AAC encoding algorithms cut the highest and lowest frequencies, and also actively use the characteristics of a person’s hearing to remove information about sounds that a person cannot easily distinguish when listening to music. . As a result of compression, AAC files do not sound identical to CD-quality files, but in general the algorithms compress the music efficiently enough that most people overlook the fact that it has been deleted. resulting sound information.

AAC Audio Format

Like MP3, the quality of an AAC file is measured by its bit rate. Common AAC bit rates include 128 kbps, 192 kbps, and 256 kbps.

Without going into technical details, here are the reasons why AAC files sound better than MP3s:

AAC encoding uses samples with a wider frequency coverage from 8 to 96 kHz; mp3 encoding uses samples with coverage from 16 to 48 kHz
Up to 48 channels can be encoded, while MP3 encodes 2 channels in MPEG-1 mode and up to 5.1 channels in MPEG-2 mode
Arbitrary bit rates and variable frame lengths are used

Higher algorithm efficiency and simpler filter banks (instead of hybrid MP3 encoding, AAC uses pure MDCT method)
Greater precision is provided when encoding AAC sound using smaller sample sizes, which are equal to 128 or 120 units, while 192 units are used for mp3 encoding. In this case, the smaller sample size allows you to code more precisely, since the original sound wave is an analog signal, and for a more accurate description, it needs to be measured as often as possible. Therefore, a smaller sample size is better because it allows you to more accurately describe the analog nature of a sound wave in digital form.

Sound frequencies above 16 kHz are processed more efficiently. Let me remind you that in mp3 format these frequencies are simply erased
More progressive algorithms are used in stereo binding mode. Let me remind you that stereo stitching allows you not to store both channels separately, as in CD-quality recording. The common signal for both channels is stored and only the difference between the channels is stored separately from each other.
Additional modules were added to improve compression efficiency: TNS, Inverse Prediction, PNS and others
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How AAC works with iTunes

Apple adopted AAC as its primary audio format. All songs stored in iTunes Store and all songs streamed or downloaded from Apple Music are encoded in AAC format. All AAC files in the Apple ecosystem are encoded at 256 kbps.

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What is the AAC format and what are the advantages over mp3?

Designated heir to MP3, it is the most widely used encoding format today. Compatible with YouTube, iPhone and Android, among others

AAC

More than twenty years of honorable career, which have allowed music to become truly “pop” and spread throughout the world, regardless of the playback device you use. This is the rather heavy legacy of MP3, a multimedia format created between the late 1980s and early 1990s by Italian engineer Leonardo Chiariglione. In its place we now find AAC, the audio file encoding standard developed by Bell Labs, Fraunhofer Institute, Dolby Labs, Sony, and Nokia at the beginning of the last century.

AAC

A lossy codec, AAC is considered a standard by both ISO (acronym for International Organization for Standardization) and IEC (acronym for International Electrotechnical Commission) and is an integral part of the MPEG-2 and MPEG-4 specifications. After a few years “in the shadow” of MP3 encoding, today AAC encoding is by far the most widespread and adopted: it is the standard or default audio format for YouTube, iPhone, iPod, iPad, Nintendo DSi, Nintendo 3DS. , iTunes, DivX Plus Web Player, PlayStation 3 and is compatible with PlayStation Vita, Wii, Sony Walkman MP3, Android and BlackBerry.

Differences from MP3 files

The reason for this success is explained by the numerous improvements that this standard presents compared to the one conceived by Chiariglione. First of all, the AAC can guarantee better audio playback quality with the same file size (and therefore bit rate). This is because AAC encoding has a greater variety of samples (8 to 96 kilohertz, as opposed to 16 to 48 kilohertz samples allowed by the MP3 format) and supports a greater number of channels of audio playback (up to 48 channels).

This is combined with the increased flexibility and flexibility of AAC encoding, which allows engineers to design and implement encoding and decoding algorithms according to their needs. This flexibility encourages real competition, leading to more efficient and effective algorithms. Translated into simple words, an audio file converted with an AAC encoder at the same bit rate will guarantee, as already mentioned, better playback quality than many other competitive lossy formats.

What is the AAC?

MP3 has practically become synonymous with online audio, as it is capable of transforming your music into small files, ideal for sharing. However, the fact of having a “reasonable” audio quality displeases many people, opening the market to other more robust formats, such as AAC (Advanced Audio Coding).

AAC (Advanced Audio Coding) Bluetooth Audio Codec

Unlike FLAC, AAC is a lossy audio compression scheme that focuses not on audiophiles, but on users who want high-quality music without sacrificing large disk space or even their portable music players to store them.

Seen by the market as a successor to MP3, this format has big names behind its development, such as Sony, AT&T, Nokia and Dolby Laboratories, and has even been standardized by renowned ISO and IEC institutes. Many of our devices already use AAC as standard, like PlayStation 3 and Portable, Nintendo Wii and DSi, Andoid devices, iPhones and iPod, being the standard format used even in iTunes.

AAC

To explain AAC’s superiority over MP3, let’s look at some points of comparison:

-AAC achieves a higher level of audio quality without increasing file size. This is measured in Kbps (Kilobits per second) and the higher this number, the more transparent the sound will be and the more space will be needed for the file. A song compressed in AAC at 96 Kbps has a clearer sound than an MP3 at 128 Kbps, which means more quality in a smaller size;
-A very important parameter to estimate the “purity” of a song is its sampling frequency, because the higher the margin, the more details are stored. While MP3 has a range of 16KHz to 48KHz, AAC ranges from 8KHz to 96KHz;
An MP3 audio file only supports 5.1 channels in MPEG-2, while AAC is capable of playing up to 48 different channels in MPEG-4;
-The above data only explains the preference of many users and companies to replace MP3, which has been standard since 1993. The only drawback seen by some manufacturers is the need to pay royalties to the Dolby Digital encoder (decoder) and AAC decoder. , but this is something that already happens with the MP3 format, so who knows with a little negotiation things will be resolved.

M4A – AAC format and characteristics

Presentation of the AAC format

AAC (Audio Advanced Coding) is an audio data compression format developed by the Fraunhofer Institute in collaboration with AT&T, Nokia, Sony and Dolby.

As with the MP3 format, it is a destruction of audio data compression, called “lossy compression” (that is, lossy compression), ie the removal of certain auditory information (for example, inaudible frequencies) to the best possible compression rate, keeping a result as close as possible to the original data.

AAC

The AAC format corresponds to the international standard “ISO / IEC 13818-7” as an extension of MPEG-2, standard of the Moving Image Expert Group (MPEG).

The AAC format was chosen by the Apple company as the primary file format on iPods or in the iTunes software.

Frequently Asked Questions: M4A – AAC Format and Features

Technical properties

AAC uses a variable bit rate encoding (Variable bit rate in English, sometimes abbreviated as VBR), that is, an encoding that allows you to adjust the number of bits used per second to encode audio data according to the complexity of current at a given moment. The algorithm used is more efficient than that of MP3, enabling smaller, higher quality files to be obtained, while requiring less resources to encode or decode.

Compared to the maximum of two channels (in stereo) supported by the MP3 format, the AAC format allows polyphonic recording of up to 48 channels. The AAC format also provides sound reproduction in the 8Hz-96.0kHz frequency band, compared to 16-48kHz for the MP3 format.

Files in AAC format, with extension .mp4 (for MPEG-4), .m4a (for MPEG-4 audio) or .m4p (for protected MPEG-4), are generally smaller than files in MP3 format.

AAC Compatibility

The AAC format is not compatible with the MP3 format, this means that you must use a player that is compatible with the format or install a specific codec so that existing players can read files in AAC format.

MP3 y AAC

However, more and more software players allow you to read files in this format, and the latest hardware MP3 players support this format.

What is the AAC format and what are the advantages compared to the mp3?

A designated heir to MP3, this is the most widely used form of encoding today. It is supported, among others, by YouTube, iPhone and Android.

Over twenty years of honest career, which has allowed music to become truly “pop” and spread around the world, regardless of the playback device used. This is the rather heavy legacy of MP3, a form of multimedia created in the late 1980s and early 1990s by Italian engineer Leonardo Chiariglione. Instead, we now find the AAC, the standard for encrypting audio files developed by Bell Labs, Fraunhofer Institute, Dolby Labs, Sony and Nokia near the end of the last century.

Lossy codec, the AAC is considered a model by both ISO (an acronym for the International Organization for Standardization) and IEC (an acronym for the International Electrotechnical Commission) and is an integral part of the MPEG-2 and MPEG-4 specifications. After a few years “in the shadows” of MP3 encoding, today AAC encoding is by far the most common and adopted: it is the standard or default audio format for YouTube, iPhone, iPod, iPad, Nintendo DSi, Nintendo 3DS, iTunes, DivX Plus Web Player, PlayStation 3 and is compatible with PlayStation Vita, Wii, Sony Walkman MP3, Android and BlackBerry.

AAC – Differences with MP3 files

The reason for this success is explained by the many improvements that this model presents compared to the one developed by Chiariglione. First of all, AAC manages to guarantee better audio playback quality for the same file size (and therefore bit rates). This is because AAC encoding has a greater variety of samples (8 to 96 kilohertz compared to 16 to 48 kilohertz samples allowed by the MP3 format) and supports a larger number of audio playback channels (up to 48 channels).

AAC – Portable music player

Added to this is the increased flexibility and flexibility of AAC coding, which allows engineers to design and implement coding and decoding algorithms according to their needs. This flexibility feeds real competition, leading to more efficient and effective algorithms. Simply put, a sound file converted to an AAC encoder at the same bit rate will guarantee, as already mentioned, better playback quality than many other competing loss formats.

How to convert MP3 to AAC

The discussion about converting between MP3 and AAC files is not entirely accurate. While the second is a real audio format used in many areas, the second is an encryption algorithm that can be used by different file formats. The most well-known, in this sense, are “.m4a”, “.mp4”, “.3gp”, “.m4b” and “.m4p”. To convert MP3 to AAC, therefore, you must select one of the forms listed above.

However, converting your MP3 music collection does not require any specific action. You need to select one of the many existing audio conversion programs (or even a special web portal for file conversion) and select the tracks or albums for editing.

AAC audio formats

When we talk about the different audio formats that we have available for our work or entertainment, we usually hear that there is the MP3 format, Dolby type sound, and in some cases it has audio in the AAC format.

This last audio format is very characteristic of some movies found on DVD discs, which comes to be a technical specification that means Advanced Audio Coding, or translated into Spanish “advanced audio coding”, and which actually comes to be an extremely important resource for those editors who work in the video area.

Working with the AAC audio format represents having a better sound quality than many of the cases is distributed to different speakers, perfectly defined in terms of the position they should occupy in an appropriate environment; In addition, this AAC audio format tends to occupy a smaller space than an MP3 audio format would occupy, which in the design of a DVD disc comes to be known as Layer 3 type audio, which is widely used in the compilation of audio and video for the formation of a DVD movie. But the important thing is that this AAC format provides high-fidelity audio quality and that many times it is used for the well-known “no-home” formats.

It is there where the conveniences of using this AAC audio format are found, since by occupying 30% less space than an MP3 audio file, having better quality and fidelity in its sound, it is widely used not only by those film editors DVD, but also by iTunes as well as by many music discs they represent today.

AAC (Advanced Audio Coding) is a digital audio signal computer format based on a lossy compression algorithm, a process by which some of the audio data is removed in order to obtain the highest possible degree of compression, resulting in an output file that sounds as close to the original as possible.

features

AAC uses a variable bit rate VBR, an encoding method that adapts the number of bits used per second to encode audio data, depending on the complexity of the audio stream at any given time. AAC is an encoding algorithm Broadband audio that has superior performance than MP3, produces better quality on small files and requires less system resources to encode and decode. This codec is oriented to broadband uses and is based on the elimination of redundancies of the acoustic signal, as well as on compression by means of the modified discrete cosine transform (MDCT), very similar to that of MP3.

Advantage

Superior audio quality for the same bitrate (kbps) your Radio at 32kbps will sound like 128kbps in mp3. Stereo sound support from 16 kbps unlike MP3 that supports it from 40 kbps. Support on Blackberry, Iphone, Smartphone equipment. Members of the codec family aacPlus aacPlus v1 is the combination of AAC and SBR, as the high-efficiency standardization profile in MPEG-4 (HE AAC). aacPlus v2 builds on the strong success story of aacPlus v1 and adds value in all fields where increased compression efficiency of stereo signals is mission critical. aacPlus v2 is a true superset of aacPlus v1, aacPlus v1 is from AAC. With the addition of Parametric Stereo in MPEG, aacPlus v2 is the current state of the art low-bit-rate open standard audio codec. Not compatible with MPEG-1. Sample Rate: 96 KHz, 88.2 KHz, 48 KHz, 44.1 KHz, 24 KHz, 22.05 KHz, 16 KHz. Maximum quality between 320 and 448 kbps (5 channels) and between 128 and 192 (2 channels) Maximum supported bitrate: From 12 kbps (in HE-AACv2 profile) to 448 kbps (in AAC-LC profile)

Three options

Highest quality (resolution at 23.43 Hz and 2.6 ms) Non prediction Scalable sampling rates

Three types of profiles:

AAC-LC: 16 KBps to 448 KBps HE-AAC: 16 KBps to 128 KBps HE-AACv2: 12 KBps to 56 KBps (most efficient profile in audio quality)

What are digital audio formats

Digital audio formats are basically containers. And the differences between them are fundamentally in:

Whether or not they are compressed.

If they are compressed, in the quality of compression.

The type of labeling they can support.
Digital audio formats

MP3

It is the best known, popular and most widely used. They are known by their “.mp3” extension.

It was developed by Moving Picture Experts Group, so that it was part of the well-known MPEG-1 and MPEG-2 standards.

Its fundamental characteristic resides in the fact that the technology behind it performs a compression of the sound sequence, resulting in a really small file, which normally occupies half of the original file. To achieve this, the loss of certain sounds is necessary, which supposedly cannot be heard by the human ear.

Audio formats

WAV

Developed by the Microsoft and IBM companies, this format, whose name comes from the acronym WAVE (Waveform Aujdio File Format), is currently one of the audio formats that do not have compression in the data, therefore they present an excellent quality.

They are known by their “.wav” extension.

On the other hand, this format has the peculiarity that it includes support for almost all current audio codecs. This makes WAV one of the most widely used formats in the field of professional sound, since the sound is captured with parameters of 44100 Hz and at 16 bits, the same quality can be obtained as on a CD.

On the contrary, one of the disadvantages of this format is that it has a limitation in recording, since it can only capture a maximum of 6.6 hours in the same file at maximum quality.

Audio formats

AIFF

The AIFF (Audio Interchange File Format) format is very similar to WAV. It was born as an answer from Apple to Microsoft’s WAV, being initially only compatible with MAC computers. Currently it can also be used in Windows.

Due to its characteristics, AIFF, together with FLAC and WAV, are usually the most widely used formats in the professional field of audio.

WMA

The WMA (Windows Media Audio) format is a music file format created by Microsoft.

One of its main characteristics is that those files that have been compressed in WMA format take up less space than MP3 files, which also implies a reduction in their quality. Therefore, it is a lossy audio compression format.

OGG

OGG audio formats are compressed audio files, which means that they have a size that allows them to be transmitted via WIFI, but at the same time they avoid the damages that are usually generated in the compression process.

For example, Spotify uses these OGG formats.

Audio formats

FLAC

When we talk about the FLAC (Free Lossless Audio Codec) format, we are referring to a codec free of audio compression and without loss of quality.

Emerged within the community responsible for the OGG project, FLAC has become one of the WAV format’s strongest competitors, due to its advantages in terms of sound quality.

Its objective is to reduce the size of the original file, eliminating data that is usually known as “waste”, without causing loss of quality.

This is the format used by the Tidal platform, the best high quality audio streaming service.

What is the difference between the different audio formats, and which should I choose?

Lossless formats: WAV, AIFF, FLAC, Apple Lossless and others

In summary, there are two types of sound quality: lossless and lossy. Lossless music preserves the sound quality of the original source – in most cases, CD – intact, on the other hand, lossy music compresses the file to save space (in exchange for decreasing quality). Lossless formats include the following formats:

–WAV and AIFF: Both are uncompressed formats, making them exact copies of the original sound source. The two formats are essentially the same quality; they simply store the data differently. AIFF was created by Apple – you will see it often in its products – but WAV is much more universal. However, since they are not compressed, they take up too much unnecessary space. Unless you are editing sound, we do not need to use this format.

–FLAC: Free Lossless Audio Codec (FLAC). It is the most used lossless codec, it is a good option if we want to store our music without losing quality. Unlike WAV and AIFF, it uses compression, taking up less space. However, it is still a lossless format, which means that the sound quality is the same as the original source, so it is better for listening than WAV and AIFF. It is also free and free software, which is useful if you like to take a look at how it works.

-Lossless Apple (Apple Lossless): Also known as ALAC, it is similar to FLAC. It uses compression, although it is made by Apple. Its compression is not as efficient as that of FLAC, so the files will be slightly larger, but it is compatible with iTunes and iOS (FLAC not). Therefore, if you use iTunes or iOS as the main software for listening to music, you should choose this format.

–APE: It is a very high lossless compression file, which means you will save more space. The quality is the same as FLAC, ALAC and other lossless files, but it is not compatible with most players. On the other hand, it makes the processor work more to decode because it is so compressed. Generally, I would not recommend using this format unless you are very concerned about space and have a compatible player.

Lossy formats: MP3, AAC, OGG and more

For day to day, we are more likely to use lossy formats. They save significantly more space, and if they have a high enough bitrate, it will be very difficult to distinguish the quality of the original source. The most commonly used formats are shown below:

–MP3: MPEG Audio Layer III, or MP3 for short, is the most common lossy format. So much so that it has become synonymous with music downloads on the internet. It is not the most efficient f-format of all, but it is certainly the most compatible, making this the first choice of lossy sounds.

–AAC: Advanced Audio Coding, also known as AAC, is similar to MP3, although slightly more efficient. Which means that the files take up less space and with the same sound quality as MP3. And, with Apple’s iTunes making it so popular, it’s as compatible as MP3.

–Ogg Vorbis: The Vorbis format, often known as Ogg Vorbis due to the use of the Ogg container, is the free software version to MP3 and

–AAC. Its main attraction is that it is not restricted by patents, but that does not affect you as a user – in fact, despite being open it is of similar quality, and much less popular than MP3 and AAC, so not all players support it. . I do not recommend it unless you are interested in being open source.

–WMA: Windows Media Audio. Microsoft’s proprietary format, similar to MP3 or AAC. It really doesn’t offer any advantage over other formats, and it’s not very well supported.

So which one should you use?

Now that we have seen the differences between each format, which one should we use for our music? In general, we recommend using MP3 or AAC. They are compatible with most players, and the quality of both is very similar to that of the original source if encoded with a high bitrate. Unless you have specific needs, MP3 and AAc are the most recommended options.

However, there is something to be said for storing music in lossless formats like FLAC. Although we probably won’t notice higher quality, it is good for storing music if you plan to convert it to other formats later – as converting from one lossy format to another. Lossy (eg from AAC to MP3) will produce lower quality files.