BS/EN 60958-4-2-2016 pdf download.Digital audio interface Part 4-2: Professional applications — Metadata and subcode (IEC 60958-4-2:2016).
This part of IEC 60958 specifies the format for coding metadata, or subcode, that relates to the audio content and is carried with it. This part of IEC 60958, together with IEC 60958-1, IEC 60958.4-1. and IEC 60958-4-4, specifies an interface for serial digital transmission of two channels of periodically sampled and linearly represented digital audio data from one transmitter to one receiver.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
IEC 60958-1:2008, Digital audio interface — Part 1: General
IEC 60958-1:2008/AMDI:2014
IEC 60958-3. Digital audio interface — Part 3: Consumer applications
I EC 60958-4-1, Digital audio interface — Part 4-1: Professional applications — Audio content
IEC 60958-4-4, Digital audio interface — Part 4-4: Professional applications — Physical and electrical parameters
ISO 646, Information technology — ISO 7-bit coded character set for information interchange
ITU-R Recommendation BS.450. Transmission standards for FM sound broadcasting at I
ITIJ-T Recommendation J.17, Pre-emphasis used on sound program circuits
3 Terms, definitions and abbreviations
3.1 Terms and definItions
For the purposes of this document, the terms and definitions given in IEC 60958-1 and the following apply.
channel status
bits carrying, in a fixed format aligned with the block, specified in IEC 60958-1. information associated with each audio channel which is decodable by any interface user
4 User data format
One bit of user data may be carried in each subframe. Different user data may be carried In each channel and may be related to the associated audio or not. Its capacity in kbit/s is therefore equal to the sampling frequency in use, in kilosamples/s, for each channel.
User data bits may be used In any way desired by the user.
Known possible formats for the user data channel are indicated by the channel status byte 1,
bits 4 to 7.
Other possible formats may be used and may or may not be standardized in future.
The default value of the user data bit is logic 0.
5 Channel status format
5.1 Channel status bit
One bit of channel status data shall be carneci in each sub-frame. Different channel status data may be carried in each channel. Their capacity in kbitls is therefore equal to the sampling frequency In use, In kilosamples/s.
NOTE The channel status for each audio signal carries Information associated with that audio signal, and thus It Is possible for different channel status data to be carried In the two subframas of the digital audio signal Examples of Information to be carried In the channel status are length of audio sample words, number of audio channels, sampling frequency, sample address code, alphanumeric source and destination codes, and emphasis.
5.2 Channel status block
Channel status information shall be organized in 192-bit blocks, subdivided into 8-bit bytes numbered from 0 to 23. The transmission format shall mark every 192nd frame to show that it carries the first bit of a block. Within each byte, the bits are numbered from 0 to 7, 0 being the first bit transmitted, so bit 0 of byte 0 is the first bit In the block. Where a byte holds a numerical value, bit 0 is the least significant bit.
NOTE In EC 60958-1, the frame that begins with preamble Z contains the first bit of a block In both channels In other transports (for example AESIO and IEC 62365) a block start flag Is used to mark the first subframe in a block, and may be applied to each channel independently
5.3.1.1 General
The following two implementations are defined: standard and enhanced. These terms are used to communicate in a simple manner the level of implementation of the interface transmitter involving the many features of channel status. Irrespective of the level of implementation, all reserved states of bits defined in 5.5 shall remain unchanged.
5.3.1.2 Standard level
The standard implementation provides a fundamental level of implementation which should prove sufficient for general applications in professional audio or broadcasting. In standard implementation, transmitters shall correctly encode and transmit all channel status bits in byte 0. byte 1. byte 2. and byte 23 (CRCC) in the manner specified in this standard.
NOTE This note apphes to the French language only
5.3.1.3 Enhanced level
In addition to conforming to the requirements described in 5.3.1.2 for the standard
implementation, the enhanced implementation shall provide further capabilities.
5.3.2 Transmitter requirement
Transmitters shall encode channel status to follow all the formatting and channel coding rules to one of the two specified implementation levels. All transmitters shall correctly encode and transmit channel status with the correct juxtaposition with respect to the Z preamble or block start (see IEC 60958.1).
5.3.3 ReceIver requirement
Receivers shall decode channel status as required by their application. Receivers shall interpret CRCC errors as needing to reject the channel status block with the error. Receivers shall not interpret any errors In a channel status block such as CRCC or block length errors as a reason to mute or alter the audio content.
The purpose of the CRCC in byte 23 is to indicate corruption of the channel status block due to switching or editing effects (for example). Due consideration should be given to the implications of any action on downstream equipment and the associated system in general.
5.4 Documentation
Documentation shall be provided describing the channel status features supported by interface transmitters and receivers.BS/EN 60958-4-2-2016 pdf download.
BS/EN 60958-4-2-2016 pdf download
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