.aac File — Advanced Audio Coding

AAC (Advanced Audio Coding) is a lossy audio codec standardized as part of MPEG-2 and MPEG-4 specifications, designed as the successor to MP3. AAC provides significantly better audio quality than MP3 at equivalent bitrates, particularly at lower bitrates below 128 kbps. The codec is the default audio format for Apple's ecosystem (iTunes, Apple Music, iPhone), YouTube, and many streaming services. AAC supports multiple profiles including AAC-LC (Low Complexity) for general use, HE-AAC (High Efficiency) for low-bitrate streaming, and HE-AAC v2 with parametric stereo for very low bitrate applications like voice. The format supports sample rates from 8 to 96 kHz, up to 48 channels, and bitrates from 8 kbps to 529 kbps per channel. AAC is typically stored in MP4/M4A containers with metadata support, though raw AAC streams (.aac) also exist. The codec is covered by patents with licensing managed by Via Licensing, unlike the now-patent-free MP3. AAC has excellent hardware support in mobile devices, car audio systems, and digital broadcasts (DAB+, DVB).