Что такое формат файла AAC?
An .aac file is an Advanced Audio Coding file that implements advanced encoding and compression for storing digital audio. Developed by MPEG (Fraunhofer IIS, Dolby, Sony, and Nokia), AAC is widely supported by players such as Music (formerly iTunes), VLC, and Windows Media Player. The .aac format is similar to MP3 but delivers better sound quality at the same bitrate and handles audio signals at 16 kHz and higher more effectively.
A bare .aac file holds a raw ADTS bitstream - distinct from the .m4a container, which packages AAC audio inside an MPEG-4 file. Common profiles include AAC-LC, HE-AAC v1/v2, and xHE-AAC (USAC), with sample rate support from 8 kHz to 96 kHz.
Безопасность и защита
РИСК: LOWRaw AAC files are passive audio data and do not execute code. The main practical risk is fake "AAC to MP3 converter" download sites bundling adware/PUPs - prefer VLC, Audacity or the FFmpeg-based converters above. Files from unknown sources should still be scanned, but the format itself carries no macro/script payload.
Детали формата
в двух словахПОЛНОЕ НАЗВАНИЕAdvanced Audio Codingтакже известен как AAC audio, MPEG-4 AAC
РАЗРАБОТЧИКMPEG (Fraunhofer IIS, Dolby, AT&T, Sony, Nokia)с 1997 (MPEG-2 Part 7); MPEG-4 AAC in 1999
КАТЕГОРИЯАудиофайлы
MIME-ТИПaudio/aac
ТИПLossy compressed audio (raw AAC bitstream, usually ADTS-framed)
СТАНДАРТОткрытый · без роялти
MAGIC BYTES · СИГНАТУРА ФАЙЛА
СМЕЩЕНИЕ
0001
HEX
FFF1
ASCII
··
A raw .aac file is normally an ADTS stream that starts with the 12-bit sync word 0xFFF; the second byte is commonly F1 (MPEG-4, no CRC) or F9 (MPEG-2). Some .aac files are ADIF streams beginning with the ASCII "ADIF". AAC stored inside an MP4 container is instead a .m4a/.mp4 file ("ftyp" at offset 4), not a raw .aac file.
Программы, открывающие файлы AAC
Windows4 apps
macOS2 apps
Linux2 apps
Android1 app
iOS1 app
Технические подробности
глубокая спецификация| MIME type | audio/aac; also audio/aacp, audio/x-aac, audio/x-hx-aac-adts |
| Magic bytes | FF F1 (MPEG-4, no CRC) or FF F9 (MPEG-2, no CRC) at offset 0; ADIF streams begin with ASCII "ADIF" |
| File structure | Raw ADTS bitstream: sequential self-syncing frames each with a 7-byte header (9 bytes with optional CRC) followed by one coded audio block |
| Frame duration | 1024 PCM samples per ADTS frame, approximately 21.3 ms at 48 kHz |
| Byte order | Big-endian |
| Compression | Lossy; Modified Discrete Cosine Transform (MDCT) with perceptual noise shaping and temporal noise shaping (TNS) |
| Audio Object Types | AAC-LC (type 2), HE-AAC v1/SBR (type 5), HE-AAC v2/PS (type 29), xHE-AAC/USAC (type 42) |
| Sample rate support | 8 kHz to 96 kHz; most common values are 44.1 kHz and 48 kHz |
| Channel support | Mono, stereo, 5.1 surround, and up to 48 discrete channels |
| Typical bitrate | 96-320 kbit/s for stereo music (AAC-LC); HE-AAC effective at 32-80 kbit/s; xHE-AAC usable from 12 kbit/s |
| Typical file size | Approximately 1 MB per minute at 128 kbit/s stereo |
| CRC integrity | Optional 16-bit CRC per ADTS frame; presence signalled by the protection_absent flag in the frame header |
| DRM support | Absent in raw .aac files; DRM applied only when AAC is wrapped in a protected MPEG-4 container (.m4p) |
| Container distinction | A bare .aac file is a raw ADTS elementary stream; AAC inside MPEG-4 is distributed as .m4a, .mp4, or .m4b |
| Выпущен | 1997 (MPEG-2 Part 7); MPEG-4 AAC in 1999 |
| Последняя версия | MPEG-4 AAC (ISO/IEC 14496-3); profiles incl. AAC-LC, HE-AAC v1/v2, xHE-AAC (USAC, 2012) |
| Открыть стандартное | Да · без роялти |
| Спецификация | www.iso.org |
Конвертации AAC
Возможно
.AAC .MP3РУКОВОДСТВО
Да - AAC надежно конвертируется в MP3 с помощью бесплатных инструментов, хотя оба формата являются форматами…
Как конвертировать
.AAC .OGGРУКОВОДСТВО
Да - AAC конвертируется в OGG на любой платформе с помощью бесплатных инструментов, таких как VLC или…
Как конвертировать
.AAC .WAVРУКОВОДСТВО
Да - конвертация AAC в WAV выполняется легко с помощью FFmpeg, VLC или fre:ac, а декодирование не приводит к…
Как конвертировать
.AAC .M4AРУКОВОДСТВО
Да - в большинстве случаев это просто перенапаковка контейнера без потерь: аудио AAC перемещается в контейнер…
Как конвертировать
Вопросы и ответы сообщества
спрошено пользователямиВопросов пока нет - станьте первым, кто спросит о файлах AAC.
Часто задаваемые вопросы
What is an AAC file?
It is a lossy compressed audio file using Advanced Audio Coding, the successor to MP3. It sounds better than MP3 at the same bitrate and is Apple/iTunes' and YouTube's default audio codec.
How do I open an AAC file?
Play it with VLC (any OS), Windows Media Player on Windows 10/11, or the Music app on Apple devices. To edit it, open it in Audacity.
What is the difference between AAC and M4A?
Same audio codec, different container. A raw .aac file is the bare AAC bitstream; an .m4a wraps that AAC audio in an MP4 container with metadata. Most 'AAC' music files are actually .m4a.
Is AAC better than MP3?
Generally yes - at the same bitrate AAC preserves more detail, especially at low bitrates and high frequencies. MP3 is more universally compatible with very old devices.
How do I convert AAC to MP3?
Use VLC (Media - Convert/Save), Audacity, or fre:ac. It is a re-encode, so there is a small quality loss; keep the original if you can.
Why won't my AAC file play on an old device?
Some older players only support MP3 or only AAC-in-MP4 (.m4a). Convert the raw .aac to MP3, or re-wrap it as .m4a, to get it playing.
Ссылки
1ISO/IEC 14496-3 - MPEG-4 Audio (AAC)www.iso.org
2Fraunhofer IIS - AACwww.iis.fraunhofer.de
