.adts File Extension

What kind of file is an .adts?

An .adts file is an Audio Data Transport Stream, usually carrying one Advanced Audio Coding (AAC) stream. ADTS puts a small header in front of every compressed audio frame. That repeated framing lets a receiver start decoding partway through a broadcast or recover after missing data, which suits streaming uses such as internet radio.¹²

The registered MIME type is audio/aac. .aac is a more common extension for the same type of standalone ADTS stream. AAC inside an M4A file instead uses an MP4 container, normally with audio/mp4.

ADTS frames begin with a 12-bit syncword of all ones. Common streams therefore start a frame with bytes such as FF F1 or FF F9, but IANA registers no single magic number. Verify several valid frame headers and lengths rather than trusting the suffix or the first two bytes alone.¹

How do I open an .adts on my computer?

VLC can play raw AAC on Windows, macOS, and Linux. FFmpeg recognizes ADTS input containing a single AAC stream and can inspect, decode, remux, or convert it.³⁴

Built-in players and browsers are less predictable. MDN documents ADTS playback in Firefox and Safari, with Firefox support depending partly on the operating system's media framework.² If a player rejects the file, first confirm that it contains valid ADTS-framed AAC and that the decoder supports its AAC profile.

Poly support for .adts

Poly can store, sync, share, version, download, and find .adts files by name. Poly does not currently infer audio/aac from the .adts suffix alone. When an upload source supplies the correct MIME type, Poly treats the file as audio, builds a waveform, reads available duration and tags, and opens it in the audio player.

Correctly classified speech can be transcribed for full-text search, while audio similarity helps find related recordings. The Poly agent can use the recognized audio and its transcript. Playback still depends on the browser decoding the particular AAC profile and stream.

History of .adts

AAC and ADTS were standardized in MPEG-2 Part 7, ISO/IEC 13818-7, in 1997. MPEG-4 Part 3 later incorporated and expanded the AAC family.¹⁵ ADTS remained useful because each frame carries enough configuration and length information for sequential transport without an MP4-style file index.

The .adts spelling explicitly names that transport framing. The more widespread .aac suffix often stores the same structure, so extension choice alone does not imply different sound quality.

Working with .adts and alternatives

Remuxing changes the wrapper without re-encoding compatible AAC. Transcoding decodes and encodes the sound again, which may be necessary for an unsupported AAC profile but can add artifacts. Keep the best original when future editing matters.