Aud
1s Silence AAC
1s Silence AAC is a Advanced Audio Coding sample generated for file format testing. It can be used to test downloads, parsers, previews, and file type detection.
silence-1s.aacType Sample
512 B DownloadAudio
AAC Advanced Audio Coding
Advanced Audio Coding is a audio format commonly identified by .aac. Use the listed signatures, MIME types, and structure notes to validate files beyond the extension.
Extensions .aac
MIME audio/aac
Magic numbers
Analyze your fileoffset 0 Advanced Audio Coding leading signature
FF F1 ..offset 0 Advanced Audio Coding leading signature
FF F9 ..Structure
- ADTS header
- AAC frame payloads
Caveats
- Do not trust the extension alone. Check the MIME type, the first bytes such as FF F1, and format-specific structure when possible.
- Container formats and damaged files can share the same opening bytes, so deeper validation may be required for production upload, preview, or conversion flows.
Detection example
SIGNATURE = bytes.fromhex("fff1")
OFFSET = 0
def is_aac(path: str) -> bool:
with open(path, "rb") as f:
f.seek(OFFSET)
head = f.read(len(SIGNATURE))
return head == SIGNATUREconst SIGNATURE = [0xff, 0xf1];
const OFFSET = 0;
// bytes: a Uint8Array / Buffer holding the start of the file
export function isAac(bytes) {
return SIGNATURE.every((byte, i) => bytes[OFFSET + i] === byte);
}package fileid
import "bytes"
var isaacSignature = []byte{0xff, 0xf1}
const isaacOffset = 0
func IsAac(b []byte) bool {
end := isaacOffset + len(isaacSignature)
if len(b) < end {
return false
}
return bytes.Equal(b[isaacOffset:end], isaacSignature)
}const SIGNATURE: &[u8] = &[0xff, 0xf1];
const OFFSET: usize = 0;
fn is_aac(bytes: &[u8]) -> bool {
bytes.get(OFFSET..OFFSET + SIGNATURE.len()) == Some(SIGNATURE)
}<?php
$signature = "\xff\xf1";
$offset = 0;
function is_aac(string $bytes): bool {
global $signature, $offset;
return substr($bytes, $offset, strlen($signature)) === $signature;
}Practical usage
Use cases
Advanced Audio Coding is used for playback, waveform processing, upload checks, duration handling, and bitrate validation. Short clips, silence, and ambient audio help expose player and conversion edge cases.
Common detection mistakes
- The .aac extension alone does not prove the file contents. Upload and conversion flows should combine extension, MIME type, leading bytes, and format-specific structure checks.
- Advanced Audio Coding can start with signatures such as FF F1 or FF F9, but related containers and damaged files may require additional validation.
Security notes
Media files can still stress decoders through corrupt metadata, extreme dimensions, long durations, or unusual chunks. Read size, dimensions, and duration before processing.
Using samples
11 samples help test duration handling, playback startup, metadata reads, and download behavior.
Sample files
11 / 11 filesAud
Lake Waves AAC 0.25s
Lake Waves AAC 0.25s is a Advanced Audio Coding sample based on Wikimedia Commons, 0.25s. It can be used to test downloads, parsers, previews, and file type detection.
01-lake-waves.aacDuration 0.25s
3.2 KB SHA-256
2740788e357ee98a612a2a70a9b33fd3f4ddbc22e51617fd269c84876d5950fdAud
Lake Waves AAC 0.5s
Lake Waves AAC 0.5s is a Advanced Audio Coding sample based on Wikimedia Commons, 0.5s. It can be used to test downloads, parsers, previews, and file type detection.
02-lake-waves.aacDuration 0.5s
5.8 KB SHA-256
414a908c8173ddcc9c743500098d191f1704997cc043a6ae0fba0dff8fb605d1Aud
Lake Waves AAC 1s
Lake Waves AAC 1s is a Advanced Audio Coding sample based on Wikimedia Commons, 1s. It can be used to test downloads, parsers, previews, and file type detection.
03-lake-waves.aacDuration 1s
12 KB SHA-256
e533d9ab2b749c8910daad148b31457474c6c05b54a9c21ee9eaa5b9d7ddf17cAud
Lake Waves AAC 1.5s
Lake Waves AAC 1.5s is a Advanced Audio Coding sample based on Wikimedia Commons, 1.5s. It can be used to test downloads, parsers, previews, and file type detection.
04-lake-waves.aacDuration 1.5s
18 KB SHA-256
bdf386e3712ed599c92c455fe0f2e479e56d69ce99a9cea0d9ba5f94882d694aAud
Lake Waves AAC 2s
Lake Waves AAC 2s is a Advanced Audio Coding sample based on Wikimedia Commons, 2s. It can be used to test downloads, parsers, previews, and file type detection.
05-lake-waves.aacDuration 2s
24 KB SHA-256
e797ec29cd833cb299ecfc374399268dc76a4955c821787e130985b85df35e1aAud
Lake Waves AAC 3s
Lake Waves AAC 3s is a Advanced Audio Coding sample based on Wikimedia Commons, 3s. It can be used to test downloads, parsers, previews, and file type detection.
06-lake-waves.aacDuration 3s
36 KB SHA-256
b11aeeffb173130ac33ed9fbb4d64028063620b3db09700c5c3510496b8cc9c1Aud
Lake Waves AAC 4s
Lake Waves AAC 4s is a Advanced Audio Coding sample based on Wikimedia Commons, 4s. It can be used to test downloads, parsers, previews, and file type detection.
07-lake-waves.aacDuration 4s
48 KB SHA-256
d7ad33a74be23f011bac3cef9f481de5c4aa702b87a98dc6f8a131d2a1938887Aud
Lake Waves AAC 6s
Lake Waves AAC 6s is a Advanced Audio Coding sample based on Wikimedia Commons, 6s. It can be used to test downloads, parsers, previews, and file type detection.
08-lake-waves.aacDuration 6s
72 KB SHA-256
8998e5ae73b0aaa07e45acb02a7d3662e608701edf8a59957edc71c424b9b7e5Aud
Lake Waves AAC 8s
Lake Waves AAC 8s is a Advanced Audio Coding sample based on Wikimedia Commons, 8s. It can be used to test downloads, parsers, previews, and file type detection.
09-lake-waves.aacDuration 8s
96 KB SHA-256
bee731063ed41057988d8a6dc29cb36751aa99fabc8d443fd58e1dfb63c3831aAud
NASA TV Audio AAC
NASA TV Audio AAC is a Advanced Audio Coding sample based on NASA Image and Video Library, 2s. It can be used to test downloads, parsers, previews, and file type detection.
nasa-tv-audio.aacDuration 2s
24 KB SHA-256
b9b88ab211128d2cebafbaa798878be5228e20cbd425e9265a8a89b6112604edFrequently asked questions
What is the magic number (file signature) of Advanced Audio Coding?
Advanced Audio Coding files begin with the byte signature FF F1 ("..") or FF F9 (".."). Detect the format by reading these leading bytes rather than trusting the file extension alone.
What is the MIME type of Advanced Audio Coding?
The MIME type for Advanced Audio Coding is audio/aac.
What file extension does Advanced Audio Coding use?
Advanced Audio Coding files use the .aac extension. The extension is a convention only and does not guarantee the file contents, so combine it with signature and structure checks.