Overview
IEC 61937-8:2006 defines how to transport Windows Media Audio (WMA) Professional non-linear PCM bitstreams over the digital audio interface specified in IEC 60958. It is Part 8 of the IEC 61937 series and specifies burst formatting, burst-info fields, repetition timing, pause handling and decoder latency requirements for WMA Professional streams mapped onto the IEC 60958 physical interface.
Key topics and technical requirements
- Mapping to IEC 60958: Defines how WMA Professional bitstreams are carried as IEC 61937 data‑bursts (burst-preamble + burst-payload) on an IEC 60958 link.
- Burst-info fields: A 16‑bit burst-info word identifies the data-type and subtype for WMA Professional and contains repetition/format information. The standard provides exact bit-field definitions for these values.
- Four WMA subtypes (Type I–IV): The standard defines four WMA Professional subtypes with different frame sizes and reference points:
- Type I - frame = 4 096 samples (intended for >48 kHz sample rates such as 88.2 kHz, 96 kHz)
- Type II - frame = 2 048 samples
- Type III - implied smaller frame (reference point Pa = 1 024)
- Type IV - implied smaller frame (reference point Pa = 512)
- Pause data‑bursts: A defined pause data‑burst format and recommended repetition period (typically three IEC 60958 frames) for filling stream gaps; includes a gap-length parameter to indicate missing decoded PCM samples.
- Latency and synchronization: Latency is defined as receiving delay(s) plus decoding delay. For Type I, latency equals two frames plus two‑thirds of a frame (examples: 123.84 ms at 88.2 kHz, 113.77 ms at 96 kHz). Transmitters should schedule bursts using these latency figures to maintain audio/video sync.
- Normative references: Requires IEC 60958 (digital audio interface) and IEC 61937 Parts 1 and 2 for general framing and burst-info conventions.
Applications and who uses it
- Hardware and firmware engineers implementing digital audio interfaces on consumer electronics (DVD/Blu‑ray players, set‑top boxes), professional audio devices, and audio decoders.
- System integrators and broadcast equipment vendors who must convey compressed WMA Professional streams over S/PDIF/IEC 60958 links.
- Test and compliance teams verifying proper burst formatting, pause handling, and synchronization/latency behavior.
- Manufacturers aiming to ensure interoperability between digital transmitters and external WMA Professional decoders.
Related standards
- IEC 60958 - Digital audio interface (physical/format basics)
- IEC 61937-1 - General mapping rules for non-linear PCM bitstreams
- IEC 61937-2 - Burst-info definitions and common fields
Keywords: IEC 61937-8, WMA Professional, digital audio interface, IEC 60958, non-linear PCM, data-burst, burst-info, latency, pause data-burst, audio synchronization.
Open preview (PDF)Digital audio - Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 - Part 8: Non-linear PCM bitstreams according to the Windows Media Audio (WMA) Professional format
