IEC 61937-11:2021

Overview

IEC 61937-11:2021 is Part 11 of the IEC 61937 series and defines how to transport non-linear PCM audio bitstreams - specifically MPEG‑4 AAC (and its extensions) and MPEG‑D USAC - over the IEC 60958 digital audio interface using the MPEG‑4 LATM/LOAS framing. This second edition (2021) is a technical revision of the 2010 edition (with 2018 amendment) and notably adds MPEG‑D USAC support. The standard enables passing AAC/USAC bitstreams from devices such as set‑top boxes to A/V receivers without reframing into ADTS, and supports both normal and high‑speed transmission modes.

Key topics and technical requirements

• Mapping to IEC 61937-1: Specifies how LATM/LOAS framed audio is encapsulated into IEC 61937 data‑bursts for transport over IEC 60958 physical interfaces.
• Data‑burst format: Defines structure for pause data‑bursts and audio data‑bursts, including burst‑info and data‑type signalling for AAC, HE‑AAC, HE‑AAC v2 and USAC in LATM/LOAS.
• Framing and LATM/LOAS details: Requirements for multiplex elements (AudioMuxElement), access unit handling and payload mapping so decoders can extract and decode streams.
• Latency and timing: Guidance and formulas (Annex A) for calculating decoding delay and required data‑burst repetition rates to ensure synchronized playback.
• High‑speed transmission: Annex B describes signalling and handling when the IEC 60958 interface does not carry an embedded sampling clock (useful for higher channel counts and modern broadcast workflows).
• Profiles and object types: Informative annex (C) summarises MPEG‑4 and MPEG‑D audio profiles and audio object types relevant to this part.
• Normative references: Requires alignment with IEC 60958 (digital audio interface), IEC 61937‑1/2 (general and burst‑info), ISO/IEC 14496‑3 (MPEG‑4 audio) and ISO/IEC 23003‑3 (MPEG‑D USAC).

Practical applications and users

Who uses IEC 61937-11:2021:

• Consumer electronics manufacturers (set‑top boxes, A/V receivers, soundbars)
• Broadcast equipment vendors and system integrators (DVB / digital TV headends)
• Firmware and codec developers implementing AAC/USAC decoders and LATM/LOAS encapsulation
• Test labs and compliance engineers verifying interoperability over IEC 60958 (S/PDIF) links
• Product architects designing low‑latency, multichannel audio transport solutions

Practical benefits:

• Enables interoperable delivery of advanced AAC and USAC audio over existing digital audio interfaces
• Avoids the need to reframe streams (no ADTS conversion)
• Supports modern broadcasting requirements and higher channel counts via high‑speed mode
• Provides timing and burst guidelines to manage latency and robust decoding

Related standards

• IEC 61937‑1: General requirements for non‑linear PCM bitstreams over IEC 60958
• IEC 61937‑2: Burst‑info definitions
• IEC 60958 (all parts): Digital audio interface (consumer/professional)
• ISO/IEC 14496‑3: MPEG‑4 AAC audio specification
• ISO/IEC 23003‑3: MPEG‑D USAC specification

Keywords: IEC 61937-11:2021, MPEG‑4 AAC, MPEG‑D USAC, LATM/LOAS, IEC 60958, digital audio interface, data‑burst, high‑speed transmission, non‑linear PCM.