IEC 61937-14:2017

Overview

IEC 61937-14:2017 specifies how to convey non-linear PCM audio bitstreams encoded in the AC-4 format over digital audio interfaces that apply IEC 60958 (commonly used S/PDIF-like framing). This part of IEC 61937 defines burst mapping, timing, and signalling so AC-4 streams can be transported reliably between consumer and professional audio devices.

Key topics and technical requirements

• Mapping to IEC 61937-1: Defines how AC-4 bitstreams are packaged into IEC 61937 burst frames and how burst-info fields are used to identify AC-4 data.
• Burst types: Specifies pause data-bursts and audio data-bursts, including repetition periods and maximum burst lengths.
• AC-4 data formats: Covers base AC-4 as well as variants for higher bit rates and low-delay modes-HBR4, HBR16, and LD-with separate burst formats and timing rules.
• Frame rates and sampling: Uses AC-4 parameters (base sampling frequencies 44.1 kHz and 48 kHz) and supports fractional audio frame rates (e.g., 23.976, 29.97 fps) with shorthand notation as in the standard.
• Latency definition: Latency for external decoders is defined as the sum of receiving delay time and decoding delay time; the standard includes latency diagrams and rules per data type.
• Sync frame and syntax: Annex A provides the normative AC-4 sync frame syntax and syncword values required for correct frame alignment.
• Normative references: Relies on IEC 60958, IEC 61937-1, IEC 61937-2 and ETSI TS 103 190 (AC-4 specification).

Practical applications and users

IEC 61937-14 is intended for equipment and system designers who need to transport AC-4 audio between devices:

• Consumer AV manufacturers (set-top boxes, Blu‑ray players, soundbars, AV receivers) implementing AC-4 over S/PDIF or similar IEC 60958 interfaces.
• Broadcast and streaming device vendors ensuring AC-4 carriage and timing compatibility in playout chains.
• Chipset and firmware engineers who implement encoder/decoder interfacing, burst framing, and latency handling.
• Test labs and compliance engineers validating burst formats, repetition periods, and latency claims.
• System integrators working on multi-room or professional audio installations that combine legacy digital interfaces with AC-4 encoded streams.

Related standards

• IEC 61937-1: General mapping for non-linear PCM bitstreams
• IEC 61937-2: Burst information
• IEC 60958: Digital audio interface (S/PDIF family)
• ETSI TS 103 190: AC-4 audio compression standard

Keywords: IEC 61937-14:2017, AC-4, IEC 60958, non-linear PCM, digital audio interface, burst-info, latency, HBR4, HBR16, LD, sync frame, ETSI TS 103 190.