AAC Description

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AAC Description

AAC

AAC is short for Advanced Audio Coding, which appeared in 1997 and was originally an audio coding technology based on MPEG-2. Co-developed by Fraunhofer IIS, Dolby Laboratories, AT&T, Sony and other companies to replace the MP3 format. In 2000, the MPEG-4 standard was introduced, and AAC reintegrated other technologies (PS, SBR). To distinguish it from the traditional MPEG-2 AAC, AAC with SBR or PS features is also called MPEG-4 AAC.

AAC - Advanced Audio Codec

AAC is a new generation of lossy audio compression technology. It derives three main encodings, LC-AAC, HE-AAC, and HE-AACv2 through some additional encoding technologies (such as PS, SBR, etc.). LC-AAC is the Compared to traditional AAC, in relative terms, it is mainly used for medium and high code rate (>= 80 Kbps), HE-AAC (equivalent to AAC+SBR) is mainly used for medium and low code (<= 80 Kbps), and the recently released HE-AACv2 (equivalent to AAC+SBR+PS) is mainly used for low bit rates (<=48 Kbps); in fact, most encoders are set to <=48 Kbps to automatically enable PS technology, and >48 Kbps does not add PS, which is equivalent to ordinary HE-AAC.

2. Brief description of AAC specification

AAC has a total of 9 specifications to meet the needs of different occasions:

MPEG-2 AAC LC Low Complexity Specification (Low Complexity): Relatively simple, no gain control, but improved

Encoding efficiency, you can find a balance point in the encoding efficiency of medium bit rate and sound quality

Main Main Specification MPEG-2 AAC

Scalable sample rate MPEG-2 AAC SSR

MPEG-4 AAC LC Low Complexity Specification (Low Complexity) —— the current mobile phone is more common in the MP4 file

The audio part of the file includes the audio file of this specification

Main Main Specification MPEG-4 AAC —— It contains all the functions except gain control, and its sound quality is the best

Scalable sample rate MPEG-4 AAC SSR

MPEG-4 AAC LTP Long Term Prediction

Low Delay Specification MPEG-4 AAC LD (Low Delay)

MPEG-4 AAC HE (High Efficiency) High Efficiency Specification—-This specification is suitable for low bit rate encoding, with

Nero ACC encoder support

Currently the most used are LC and HE (suitable for low bit rates). The popular Nero AAC encoding program only supports the three specifications of LC, HE and HEv 2. For AAC audio encoded, the specifications are displayed in LC. HE is actually AAC(LC)+SBR technology, HEv2 is AAC(LC)+SBR+PS technology;

Hev1 and HEv2 are simply represented by this diagram:

(AAC in the figure refers to the original AAC-LC)

HE: “High Efficiency.” HE-AAC v1 (also known as AACPlusV1, SBR) implements AAC(LC)+SBR technology by means of a wrapper. SBR actually stands for Spectral Band Replication. Briefly describe, the main spectrum of music is concentrated in the low-frequency band, and the high-frequency band has a small but important amplitude, which determines the sound quality. If the whole frequency band is encoded, if it is to protect the high frequency, the low frequency band will be encoded too precisely and the file will be huge; if the main low-frequency component is preserved and the high-frequency component is lost, the sound quality will be lost. SBR cuts the frequency spectrum, the low frequency is encoded separately to save the main components, and the high frequency is amplified and encoded separately to save the sound quality. It is “built-in”, and the sound quality is also preserved in the case of reducing the file size, which perfectly resolves this contradiction.

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Introduction to AAC audio encoding

AAC audio coding format, the full name is “Advanced Audio Codec”.

AAC Audio

This state-of-the-art, advanced encoding standard was jointly developed by Fraunhofer IIS (former MP3 standards maker), Dolby, AT&T, Sony, Apple, and other industry giants. AAC audio coding technology was formulated as early as 1997. At that time, it was used as one of the MPEG2-AAC audio coding specifications in MPEG-2. Later, it was used in MPEG-4 in 2000 (ISO 14496-3 Audio), so now it changed to the MPEG-4 AAC standard, that is, AAC has become one of the main members of the MPEG4 family, which is the audio coding system in the third part of MPEG4. AAC provides up to 48 channels of full-range audio. Among them, AAC audio coding is divided into nine specifications in different fields: MPEG-2 AAC main MPEG-2 AAC LC (low complexity) MPEG-2 AAC ××× (scalable sampling rate) MPEG-4 AAC main MPEG -4 AAC LC (Low Complexity) MPEG-4 AAC ××× (Scalable Sample Rate) MPEG-4 AAC LTP (Long Term Prediction) MPEG-4 AAC LD (Low Delay) MPEG-4 AAC HE (High Efficiency) AACPlusV1/V2( 3GPP ) Among them, the first three estimates are difficult to apply, and among the last six, LC and HE are the most used, so these two are mainly introduced:

MPEG-4 AAC LC (Low Complexity) is the most widely used specification, we call it “low complexity specification”, we call it “LC-AAC” for short, this specification can strike a balance in terms of coding efficiency and sound quality . at the half bit rate point. The so-called average bit rate refers to the bit rate between 96 kbps and 192 kbps. So if you want to use the LC-AAC specification, please try to control the bitrate within the range mentioned above. In this range, LC-AAC can completely beat MP3 with the highest quality LAME slow encoding mode at the same bit rate. In my opinion, whether it is a Walkman or streaming music over the Internet, it is recommended to use the LC-AAC 128kbps-192kbps encoding specification. MPEG-4 AAC HE (High Efficiency) AACPlusV1/V2(3GPP), we call it “High Efficiency Specification”, we call it “HE-AAC” or “AACPlus” for short, this specification is suitable for low bit rate encoding bits, because this specification also incorporates the type of SBR technology in Mp3Pro. When you need to encode audio files between 32 kbps and 96 kbps, it is recommended to prefer the “HE-AAC” encoding specification. With this spec, you can easily kill Microsoft formats like WMA9 and WMAPro within this range at the same bitrate. If you’re a fan of audio novels or radio dramas, consider the He-AAC specification, which can provide crystal-clear vocal dialogue even at a very low bitrate.

So if you need to encode AAC at relatively high bit rates (192kbps-384kbps or more), how should you choose? If your bit rate does not exceed 256kbps (eg: 192kbps-256kbps), “LC-AAC” can also be applied. If you really need a higher bit rate, choose the Main encoding (main specification). At high bit rate, AAC can also easily beat the very popular Lame MP3, even 320kbps CBR MP3 is not Mian-AAC’s opponent at all. Even many people believe that the LC-AAC medium bit rate, 192kbps CBR has reached the sound quality of 320 CBR Lame MP3. Of course, only the MPC format can compete with high-bitrate AAC, but the MPC format is too versatile. Having said that, there is no need to use high bitrate AAC, and Main-AAC will have problems in some general purpose or ××× players, because the sound quality of LC-AAC mentioned above is good enough, and the versatility is good. If you are an audiophile, just use lossless, like FLAC etc.

Is the effect the same when playing poor quality songs on good speakers and playing poor quality songs on poor speakers?

Speakers

First, if a song (sound source) with poor recording quality is played back with good sound, the effect will be worse initially. The meaning of high fidelity is that it largely restores to the state at the time of recording and tries not to lose it.

Speakers

The better the sound, the better the sound source can be restored with the best effect. On the contrary, if a sound source with poor sound quality is played by a good speaker, it will also expose faults and failures.

Second, the sound source in lossless format is played back with poor sound. Relatively speaking, as long as the sound isn’t particularly bad and the high, mid, and low frequencies are balanced, it won’t be too unpleasant, but the expressiveness and detail aren’t good enough.

3. The so-called lossless is just an encoding format, it doesn’t mean the lossless effect is necessarily good, and it also depends on the recording level or environment. For example, recordings of live performances, even in lossless formats, are not as good as studio recordings.

Fourth, the sound source and sound are equally important. Good sound is not necessarily expensive, the effect is only related to personal understanding and desire, but not necessarily to price.

Depending on the sound quality, 128kbps mp3 is relatively poor, and there are many lossless types, but in my opinion, the sound is the most important, only if the sound is good, you can know whether the sound quality of the song is good. otherwise you will use dozens of blue. What is the difference between the Bud small speaker that plays lossless and mp3? I’m not a part of the team, and I don’t recommend buying all kinds of hi-fi playback devices, but you still need to buy one for a few dollars. Headphones In principle, I don’t recommend using headphones if they’re not good enough. Preferably “flat response”.

Is there a difference between the sound quality of AAC and lossless format?

What a big difference!

AAC

Common lossless sound quality is APE, FLAC, etc. AAC does not fall into the category of lossless sound quality.

AAC uses the smallest volume to get the best format that is close to lossless sound quality, but there is still distortion compression after all.

An APE song is a few tens of MB, while AAC is only a few MB.

ACC

Advanced Audio Coding ACC (English: Advanced Audio Coding, AAC), based on MPEG-2 audio coding technology. Co-developed by Fraunhofer IIS, Dolby Laboratories, AT&T, Sony (Sony) and other companies, the goal is to replace the MP3 format. In the year 2000, after the appearance of the MPEG-4 standard, AAC reintegrated its features and added SBR technology and PS technology. To distinguish it from the traditional MPEG-2 AAC, it is also called MPEG-4 AAC.

APE is one of the popular distortion-free compression formats for digital music, compressed by Monkey’s audio software.

Compared with the similar FLAC file format, ape has error checking ability but does not provide error correction function to ensure pure and lossless files; another feature is that the compression rate is about 55%, which is higher than that of FLAC, and the volume is about half of the original CD, for easy storage.

FLAC

FLAC is a well-known free audio compression codec, which is characterized by distortion-free compression. Unlike other distorted compression codes like MP3 and AAC, it will not destroy any original audio data, so it can restore the sound quality of music CDs. It has been supported by many software and hardware audio products since 2012.

Compared with APE, the FLAC format file is a little larger by 2%-3%, but the advantage of FLAC lies in the faster encoding and decoding speed, and the CPU computing power requirement is quite low, and the format is also very fault-tolerant, even if a small piece of music is damaged, and does not affect subsequent music playback.

AAC vs AC3 – Difference between AAC and AC3

ACC vs AC3

Difference between AAC and AC3

AAC vs AC3: A Battle of Audio Codecs

AAC vs AC3 is a common comparison in the realm of audio codecs, with both formats vying for dominance in digital audio compression. Advanced Audio Codec (AAC) is renowned for its superior sound quality and efficient compression, making it the preferred choice for various applications like online streaming, mobile devices, and digital radio. It has gained popularity due to its ability to deliver high-quality audio at lower bit rates, resulting in smaller file sizes while maintaining impressive sound fidelity. On the other hand, AC3, also known as Dolby Digital, has long been used in home theater systems and DVDs. While it may not match AAC in terms of compression efficiency, AC3 offers compatibility with a wide range of devices and audio systems, making it a reliable option for surround sound setups and media distribution.

The debate over AAC vs AC3

The debate over AAC vs AC3 often centers on audio quality and device support. AAC boasts better audio quality at similar bit rates compared to AC3, making it ideal for audiophiles and those seeking a more immersive listening experience. Its widespread support across platforms like iOS, Android, and major media players ensures seamless playback on various devices. Additionally, AAC’s integration in popular streaming services further solidifies its position as the go-to choice for digital content distribution. Conversely, AC3 remains prevalent in the entertainment industry, particularly for DVDs, Blu-rays, and older home theater systems. Its legacy support and compatibility with a vast array of multimedia players ensure that AC3-encoded content remains accessible and relevant.

Choosing between AAC and AC3

When choosing between AAC and AC3, several factors come into play, depending on the intended application. For creators and content distributors looking to deliver high-quality audio over bandwidth-constrained networks, AAC emerges as the frontrunner. Its efficient compression and exceptional sound reproduction make it a top pick for streaming platforms and online media consumption. Conversely, AC3 finds favor in scenarios where backward compatibility and compatibility with legacy systems are critical, such as DVD and Blu-ray distribution. Ultimately, the decision between AAC and AC3 hinges on the specific requirements of the project, the target audience, and the ecosystem of devices where the audio content will be played, making it essential for content creators to carefully evaluate their needs before settling on the ideal audio codec.

How to convert to AAC / AC3

“What is the difference between AC3 and AAC? I want to compress PCM and convert it to AAC / AC3 to save free space, but I don’t know which is better. AAC is more efficient and sound quality than AC3. I heard that it is OK. For example, I’m compressing from the same source, but which is better compared to a 256 kbit AAC file or a 384 kbit AC3 file? ”
Many people would like to ask. When I want to extract audio files from video files or Blu-ray / DVD, I don’t know which one to choose, AC3 or AAC. In this article, we will explain the difference between AAC and AAC, compare the advantages and disadvantages of each, and how to convert DVD to AC3 / AAC.

AC3, also known as Dolby Digital (audio code number 3), is an audio format developed by Dolby Laboratories, Inc. Originally, AC3 was widely used in 5.1 channels and is similar to Dolby Pro Logic. AC3 is often used for 384 kbps and 448 kbps DVD or laser discs. It is also used in 640 kbps movies.

AAC, also known as advanced audio coding, is an irreversible audio format standardized as part of the MPEG-4 specification. Developed as a successor to MPEG Layer III (MP3). AAC can transfer any bit rate from AC3 and compress data better, but it is considerably more complex than AC3. However, AAC excels with an output of 400 Kbps on 5.1 channels and 180 Kbps on dual channels.

aac-vs-ac3

Besides Movie / DVD / Blu-Ray projects, I rarely use AC3. The AC3 Dolby Digital format is mainly used for videos only. Generally, you cannot encode or decode without the use of specially licensed software or hardware.

In general, AC3 appears to be an irreversible format, but not all encoded AC3 files are irreversible. It can be encoded in lossless AC3 format. Of course, this is better than using the irreversible AAC format.

When asked which codec produces the best sound, assuming AAC or AC3 is used to encode the audio at similar bit rates, the results may be similar. However, the AAC can be a bit better. The main reason is that AAC appeared a few years after AC3, and is recognized as an excellent codec in many respects compared to MP3 (very similar to AC3).

Part 2: Advantages and disadvantages of AC3 and AAC
What are the advantages and disadvantages of AC3 and AAC? The following detailed comparison table will explain it clearly and easily.

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CAA
1. As part of the ISO standardized MPEG-4 specification, AAC supports multiple sample rates (8000-96000 Hz), bit depth, and multi-channel (up to 48 channels).

2. Various implementations are available, such as free and high-quality implementations. Therefore, anyone can implement it.

3. AAC audio files are compatible with more devices and players.

4. AAC audio files create small digital audio files.

AAC comes in a variety of formats, including AAC LC, AAC HE, and AAC PS. Therefore, it is not possible to play valid AAC files with multiple players (LC compatible only).
AC3
1. AC3 only supports full-range channels, but the sound quality is much better. It can also be backward compatible.

2. AC3 has now become the industry standard for DTV and DVD media, so almost all the latest DVD movies come with a DVD soundtrack program.

3. For high quality audio, AC3 is widely used for HDTV, DVD and Blu-ray.

Supports up to 5.1 channel audio CDs.

Dolby digital is limited to a maximum of 448 kbps.

AAC is the default audio format for iPhone, iPod, iPad, Nintendo DSi / 3DS, iTunes, DivX Plus web player, and PS3. It is also compatible with PS Vita, Wii (Photo Channel Update), Sony Walkman MP3 series and later Sony Ericsson. And mobile phones based on Nokia, Android, BlackBerry and webOS. Most car audio manufacturers also use AAC.

AC3 (Dolby Digital) is widely used in broadcasting HDTVs, DVDs, Blu-ray discs, and game consoles.

As part of the standardized MPEG-4 specification, AAC Codex creates small digital audio files, so you can store audio files in less space while maintaining high-quality sound.