.loas File Extension

What kind of file is a .loas?

A .loas file is a Low Overhead Audio Stream. It normally carries Advanced Audio Coding (AAC) audio arranged with the Low-overhead MPEG-4 Audio Transport Multiplex (LATM), then wrapped in LOAS AudioSyncStream framing. LATM describes how the audio and its configuration are multiplexed. LOAS adds synchronization and frame-length information so a receiver can find the next unit in a continuous stream.¹²

IANA registers .loas with the audio/aac MIME type. The first LOAS AudioSyncStream frame has the 11-bit syncword 0x2B7; the following 13 bits give its multiplex-element length. Check several frames and their declared lengths because the suffix or one matching bit pattern is not sufficient validation.¹³

How do I open a .loas on my computer?

FFmpeg recognizes LOAS input and provides an AAC-LATM decoder on Windows, macOS, and Linux. Use ffprobe recording.loas to inspect the codec, sample rate, channels, and duration, or ffplay recording.loas for quick playback. FFmpeg can also create LOAS/LATM output and associates its muxer with both .latm and .loas filenames.³⁴

Built-in music apps and browsers are less reliable with this transport. If playback fails, confirm that the file contains valid LOAS framing and that its AAC profile is supported. For routine listening or web delivery, an MP4-based audio file is usually easier to handle.

Poly support for .loas

Poly can store, sync, share, version, download, and find .loas files by name. Poly does not currently infer audio/aac from the .loas suffix alone. When an upload source supplies that MIME type, Poly can treat the file as audio, read available duration and tags, build a waveform, and open it in the audio player.

Correctly classified speech can be transcribed for full-text search, while audio similarity can help locate related recordings. The Poly agent can use recognized audio and its transcript. Actual playback still depends on the browser decoding the AAC profile and LOAS/LATM stream.

History of .loas

LATM and LOAS are transport tools from MPEG-4 Audio, standardized in ISO/IEC 14496-3. They were designed to carry MPEG-4 audio with low multiplexing overhead. Broadcast specifications adopted them for AAC delivery: ETSI's DVB specification requires HE-AAC data to be formatted as a LATM AudioMuxElement inside a LOAS AudioSyncStream, whose syncword supports stream synchronization.²

The .loas suffix names the outer synchronization layer. .latm is also used by media tools for the closely coupled LATM/LOAS form, so content inspection matters more than the spelling.

Working with .loas and alternatives

Remux compatible AAC when only the wrapper needs to change. Transcode when the destination cannot decode the AAC profile. A lossless export prevents additional codec loss during editing, but it cannot restore detail already discarded by AAC.