Layouts and ENCODE AS
The stream takes its layout from the bus the plugin sits on. The header shows it as the layout and the channel count (5.1 · 6 CH), and LEVELS labels each meter with its speaker (L, R, C, LFE, Ls, Rs and so on).Supported layouts
The plugin sends every channel in IAMF’s speaker order whatever order your DAW keeps them in, so a 7.1.4 bus plays its heights from the listener’s height speakers and its rear surrounds from the rears.
IAMF names mono, 2.0, 3.1.2, 5.1, 5.1.2, 5.1.4, 7.1, 7.1.2, 7.1.4 and 9.1.6 directly. The other layouts travel inside the next larger of those with the missing speakers silent (5.0 inside 5.1, 7.0.4 inside 7.1.4, 7.1.6 and 9.0.4 inside 9.1.6, for example). Relay billing counts your layout’s channels, and the listener’s browser renders the stream to their own speakers as it does any other.
Numbered channels
A bus whose layout is not one of the named ones above is streamed as numbered channels. The header shows the count (8 CH), the meters are labelled 1 to 8, and channel 1 of your bus arrives as channel 1 at the other end. The listener page names the channels by number in its routing matrix, plays them as sent, and leaveslayout for named streams; a plugin in RECEIVE puts each channel on the same-numbered channel of its track. Relay billing counts the channels of the bus.
Ambisonics
An ambisonic bus (first to third order, ACN channel order, SN3D normalisation, the AmbiX convention) is sent as IAMF scene-based audio, and the header notes AMBISONICS (ACN, SN3D) ARE SENT AS IAMF. The meters are labelled with the ACN numbers, A0 to A15. The listener’s browser decodes the scene to their speaker layout or to binaural.ENCODE AS
ENCODE AS sends the bus as it is, marked (bus) in the list, or as a smaller layout made with IAMF’s own downmix. Use it when the listener has fewer speakers than your bus, or to reduce the channel count a relayed stream is billed for (see Pricing). The downmix uses the IAMF reference coefficients and only ever reduces: surround 7 to 5 to 3 to 2 to 1, and heights 4 to 2 to 0. LFE is carried down to 3.1.2 and left out below it. Ambisonic buses reduce by order (3OA to 2OA or 1OA), which keeps the first channels of the scene unchanged.
The list shows only targets the bus can reach. Layouts with wide speakers or a six-speaker top layer sit outside IAMF’s downmix chain, so they are always sent as they are; the listener’s browser can still render them to a smaller layout at the other end.
While a downmix is selected, the header notes IAMF DOWNMIX FROM 7.1.4 BUS (with your bus’s name), and the meters show the downmixed channels. A downmix sums channels, so watch the meter labels: a label inverts at 0 dBFS, and STREAM GAIN brings the streamed copy down without touching your mix.
ENCODE AS is saved with your DAW session and fixed while streaming. If the bus changes to a layout that does not offer your saved choice, the plugin sends the bus as it is.