AAC: Advanced Audio Coding

Overview

AAC (Advanced Audio Coding) is a lossy audio compression format designed as the successor to MP3. Developed as part of the MPEG-2 and MPEG-4 standards, AAC provides better sound quality than MP3 at the same bitrate.

AAC is the default audio format for Apple's iTunes, iPhone, iPad, and YouTube, making it one of the most widely used audio formats today. It offers improved compression efficiency and better sound quality, especially at lower bitrates.

History

Development History

• 1997: AAC standardized as part of MPEG-2
• 1999: MPEG-4 AAC with additional tools
• 2003: Adopted by iTunes Music Store
• 2007: Became default format for iPhone
• 2010s: Adopted by YouTube and major streaming services

Features and Capabilities

Key Features

• Better sound quality than MP3 at same bitrate
• Support for up to 48 audio channels
• Variable bitrate (VBR) encoding
• Multiple profiles (LC, HE-AAC, HE-AAC v2)
• DRM support (FairPlay, PlayReady)
• Streaming optimization
• Low-delay coding for real-time communication

Common Use Cases

Common Uses

• Music streaming: Spotify, Apple Music, YouTube
• Mobile devices: Default format for iPhone and Android
• Digital broadcasting: DAB+ radio
• Video streaming: Audio track for online video
• Podcasting: High-quality podcast distribution

Advantages & Disadvantages

Advantages

• Superior quality to MP3 at same bitrate
• Efficient compression for streaming
• Wide device and software support
• Multi-channel audio support
• Optimized for low bitrate streaming

Disadvantages

• Lossy format (quality loss)
• Patent-encumbered (licensing required)
• Not universally supported on older devices
• More CPU-intensive encoding than MP3

Technical Information

AAC uses psychoacoustic modeling to achieve better compression than MP3 while maintaining higher quality.

Technical Specifications