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IAMF in Orbit Lite
IAMF 2.0
The Alliance for Open Media approved IAMF v2.0.0 as a final specification on 24 August 2026. Orbit Lite 1.3.1 for Mac plays files the way the approved specification describes: every profile opens, including the new Base-Advanced, Advanced-1 and Advanced-2. Files authored to v1.1 always work.
IAMF (Immersive Audio Model and Formats) is a spatial audio format built for streaming. Where an ADM BWF master carries uncompressed audio, IAMF carries coded audio (Opus, FLAC, AAC or LPCM) with the spatial structure beside it, so a file of tens of megabytes holds the same immersive mix as a multi-gigabyte ADM BWF. Eclipsa Audio is the name IAMF goes by on YouTube and other platforms. Orbit Lite plays IAMF through the same monitoring chain as ADM.
What's in an IAMF file
IAMF is maintained by the Alliance for Open Media, and the approved IAMF v2.0 specification is public. Files end in .iamf (the raw stream) or .mp4 (IAMF in an MP4 container, optionally with video). Orbit Lite opens both, and plays the picture when the MP4 has a video track.
Inside, a file describes:
- Audio Elements, the spatial building blocks (see below).
- Mix Presentations, one or more authored mixes of those elements, each with its own gains and loudness measurements.
- Codec Configs, which say how the audio is coded.
The three Audio Element types
| IAMF term | ADM equivalent | What it is | Solo button |
|---|---|---|---|
| Channel-Based | Bed | Fixed-layout audio: stereo, 5.1, 7.1.4 and so on | Channel |
| Object-Based | Object | A source with its own position, which can move | Obj |
| Scene-Based | Ambisonics | Higher-Order Ambisonics (HOA), a whole sound field | HOA |
The footer's solo buttons use IAMF's words when an IAMF file is open. See Monitoring Modes.
Mix Presentations
An ADM programme is one authored mix. An IAMF file can carry several Mix Presentations: a full mix and an alternate, for example, or language versions. Orbit Lite loads them all. Choose one from the Mix pill. See Content Switching.
Profiles
A profile is a level written into the file. It caps how many Audio Elements and channels a mix can use, and which kinds of element. IAMF 2.0 defines six profiles, and Orbit Lite 1.3.1 opens all of them. The limits apply to each Mix Presentation, counting every element's channels before they're mixed.
| Profile | Defined in | Element types | Elements · channels |
|---|---|---|---|
| Simple | IAMF 1.0 | Channel-Based or Scene-Based | 1 · 16 |
| Base | IAMF 1.0 | Channel-Based and Scene-Based | 2 · 18 |
| Base-Enhanced | IAMF 1.1 | Channel-Based and Scene-Based | 28 · 28 |
| Base-Advanced | IAMF 2.0 | All three, but objects not mixed with the others in the first mix | 18 · 18 |
| Advanced-1 | IAMF 2.0 | All three, in any combination | 18 · 18 |
| Advanced-2 | IAMF 2.0 | All three, in any combination | 28 · 28 |
Object-Based elements are new in IAMF 2.0, so only the three 2.0 profiles can carry objects.
- Simple — a single Audio Element of up to 16 channels: one channel-based bed, such as 7.1.4, or one Ambisonics scene up to third order.
- Base — up to two Audio Elements and 18 channels, with no more than one of them scene-based. The specification's example is third-order Ambisonics (16 channels) with a non-diegetic stereo (2 channels).
- Base-Enhanced — up to 28 Audio Elements and 28 channels, such as third-order Ambisonics (16 channels) with a 7.1.4 bed (12 channels). Channel- and scene-based elements only.
- Base-Advanced — the first 2.0 profile, and it does carry objects: up to 18 Audio Elements and 18 channels. When a Base-Advanced file has objects, its first Mix Presentation must hold objects only, with no channel- or scene-based elements. A player that can't mix objects with beds or Ambisonics plays that first mix. A Base-Advanced file can also use two codecs, as long as one of them is LPCM.
- Advanced-1 — any combination of channel-based, scene-based and object-based elements in the same mix, up to 18 Audio Elements and 18 channels. The specification's example is first-order Ambisonics (4), a non-diegetic stereo (2), an LFE (1) and 11 objects (11).
- Advanced-2 — everything Advanced-1 allows, up to 28 Audio Elements and 28 channels.
As of 14 October 2026, YouTube takes Simple and Base. A file's profile is shown in Diagnostics. The full rules are in section 4 of the IAMF v2.0 specification.
Orbit Lite renders up to 128 objects. A file with more is refused when it opens, with the reason, rather than losing objects silently.
Files from early Orbit betas
Object files written by Orbit betas before 1.6.0 beta 7 use a draft object format from before IAMF 2.0 was approved. Orbit Lite still plays them.
Codecs
Orbit Lite plays all four codecs IAMF defines: Opus, FLAC, AAC-LC and LPCM.
Layouts
Every channel-based layout decodes to Orbit Lite's 7.1.4 bus, and from there to binaural, stereo or your speakers: mono, stereo, 5.1, 5.1.2, 5.1.4, 7.1, 7.1.2, 7.1.4, 3.1.2, and the binaural layout.
When part of a file can't be played
IAMF 2.0 is a large specification, and Orbit's audio engine is our own. We're always adding support for more of it, with the aim of making Orbit the most complete renderer for IAMF and ADM, and for the formats that follow. Until a feature is supported, Orbit Lite tells you rather than guessing.
A file Orbit Lite can't open at all says why in one sentence, such as "This IAMF file uses a profile Orbit doesn't support yet".
When a file opens but part of it uses something Orbit Lite can't play yet, that part is either silenced or plays differently. Either way, the IAMF section of Diagnostics names it.
Silenced
The Audio Element stays silent, so you never hear it played wrong:
- one written for an expanded loudspeaker layout, new in IAMF 2.0 (such as 9.1.6 or 7.1.5.4);
- Ambisonics above third order;
- objects whose positions are written in Cartesian coordinates, or a coupled object pair;
- an element coded with a second codec, when the file uses two.
Plays differently
You hear the whole mix, but one detail isn't applied the way the file describes:
- A mix built from more than one sub-mix. A sub-mix is a part of a Mix Presentation that carries its own loudness measurement. A file usually has them because two IAMF files were merged into one. Orbit Lite plays the sub-mixes added together, without matching their loudness first, so one can sound louder than intended.
- An element gain offset. IAMF 2.0 lets a Mix Presentation turn an Audio Element up or down by a fixed number of dB. Orbit Lite plays the element without that offset, at the level it was coded at.
- An object that moves differently in different mixes. IAMF 2.0 lets each Mix Presentation give the same object its own movement. Orbit Lite keeps one movement per object, from the first mix that gives it one. In any other mix that object follows that first mix's movement.
Check a file in Diagnostics
With an IAMF file open, Preferences ▸ Diagnostics has an IAMF section:
- Profile — the file's profile, plus its additional profile when that differs.
- Silenced — each part playing silent, and why.
- Plays differently — each part that plays, but not quite as written.
If the section lists nothing beyond the profile, every part of the file plays as written.
Checking an IAMF delivery
- Play every Mix Presentation, not just the first. Each is an authored mix a listener can get.
- Compare with the ADM master. Open the ADM BWF, then the IAMF, in the same monitoring mode. Content that's in one and not the other stands out.
- Look at Diagnostics before you sign a file off. Anything silenced there is silent for you, and may play differently elsewhere.
Further reading
- IAMF v2.0 specification, from the Alliance for Open Media.
- Introducing Eclipsa Audio, Google's announcement of the Eclipsa Audio project.
- Eclipsa Audio plugin, Google's open-source plugin for authoring Eclipsa Audio in a DAW.