Digital audio interface
BS EN IEC 60958-5:2021 pdf free.Digital audio interface Part 5: Consumer application enhancement.
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
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one-bit audio
one-bit length audio data stream
Note 1 to entry: A one-bit audio data stream can be directly played back through the analogue low-pass flter bit by bit (MSB first).
3.2 high-precision multi-bit linear audio linear PCM audio data longer than 25 bits length per sample.
4 Interface format
The interface format as defined in IEC 60958-1 and IEC 60958-3 shall be used unless otherwise
specified in this document.
5 Operation modes
5.1 General
IEC 60958-1 specifies single- and two-channel operation modes. This document introduces several new operation modes based on the same interface format of IEC 60958-1 without the pre-emphasis function defined in IEC 60958-3. Channel status information identifies these modes in operation. This document shares the information with IEC 60958-1 and IEC 60958-3 and specifies new usages.
5.2 Multichannel linear PCM operation mode
In multichannel linear PCM operation mode, the samples taken from multichannel linear PCM are transmitted by time multiplexing in consecutive sub-frames.
A multichannel group is composed of several multichannel by consecutive frames. The number of multichannels included in the group is identified by the multichannel count of channel status bits 44 to 47. The group starts with preamble “B and repeats itself with no break in the block and without un-grouped frames. The group is divided into one or two multichannel subgroups by the multichannel configuration of channel status bits 49 to 60 and the multichannel map of channel status bits 64 to 165. The subgroup is composed of some specific multichannels by consecutive sub-frames. Each multichannel within the multichannel subgroup B is re-numbered according to the multichannel number of channel status bits 64 to 165. Each channel carries consecutive audio sample words.
An example is shown in Figure 1 and Table 1. The multichannel group is composed of eight multichannels. This number of eight is identified by the multichannel count value of 1 1 10. The multichannel subgroup A is composed of three multichannels identified by the multichannel configuration value of 100001010000, which includes FrontLeft channel, FrontRight channel and FrontCenter channel given in ITU-R BS.2094-1. The multichannel subgroup B is composed of the 77”’ multichannel (channel label ID name of HFL) and 78th multichannel (channel label ID name of HFR) by setting the channel status bit 77 to 1” and the channel status bit 78 to p1”. Channels of multichannel order 6. 7 and 8 are not used in this example.
The sampling frequency of each audio multichannel is identical and identified by the original sampling frequency of channel status bits 36 to 39. The sampling frequency of channel status bits 24 to 27, 30 and 31 identifies the IEC 60958 frame rate in operation.
In one-bit audio operation mode, the samples taken from multichannel one-bit audio stream are transmitted by time multiplexing in consecutive sub-frames. The sub-frame format is shown in Figure 2.
Time slots 4 to 19 carry on-bit audio samples composed of 16 bits of the consecutive one-bit audio stream. Significant bit (MSB) is carried by time slot 19.
Time slots 20 to 17 are not used: they are filled with zeros or a few fixed patterns and ignored.
The frame format as defined in multichannel linear PCM operation mode is used for multichannel one-bit audio operation mode.
The sampling frequency of each one-bit audio channel is identical and identified by the original sampling frequency of the channel status bits 36 to 39, which is 16 multiples of that of the multichannel linear PCM. The sampling frequency of channel status bits 24 to 27, 30 and 31 identifies the IEC 60958 frame rate in operation. IEC 60958-3 defines the original sampling frequency where one-bit audio multiples 16 and sampling frequency as the IEC 60958 frame rate.
5.4 High-precision multi-bit linear audio operation mode
In the high-precision multi-bit linear audio operation mode, the samples taken from the multichannel high-precision multi-bit linear audio are transmitted by time multiplexing in consecutive sub-frames dividing of word. The sub-frame format of 32/64-bit mode is shown in Figure 3. The frame formats are shown in Figure 4 and Figure 5.
In 32-bit audio operation mode, time slots 4 to 19 carry 1 6-bit samples of 32-bit audio words. Significant bit (MSB) is carried by time slot 19. Time slots 20 to 17 are not used; they are flled with zeros or a few fixed patterns and ignored.
The frame format as defined in the multichannel linear PCM operation mode is used for
multichannel 32-bit operation modes.
The original sampling frequency for the 32-bit mode corresponds to 1/2 of that of the
multichannel linear PCM.In 64-bit audio operation mode, time slots 4 to 19 carry 16-bit samples of 64-bit audio words.
Most significant bit (MSB) is carried by time slot 19. Time slots 20 to 17 are not used; they are illed with zeros or a few fixed patterns and ignored.
The frame format as defined in the multichannel linear PCM operation mode is used for multichannel 64-bit operation modes.
The original sampling frequency for 64-bit mode corresponds to 1/4 of that of the multichannel linear PCM.
6 Channel status
6.1 General
The channel status format as defined in IEC 60958.1 and IEC 60958-3 shall be used unless this document specifies.
6.2 Application
6.2.1 Channel status general format
For each IEC 60958-5 channel, the channel status block provides the information described in this clause and summarized in Table 2.
A channel whose channel number is XX in IEC 62574:2020 is mapped on bit XX. Each bit XX is named by the corresponding channel label ID name in IEC 62574:2020, shown in Table 2.
7 Stream change
IEC 60958-1:20—, Annex F introduces stream change procedure; switching from linear PCM to nonlinear PCM, switching from nonlinear PCM to linear PCM, and switching from nonlinear PCM to another nonlinear PCM.
This document adopts the same switching procedure as one defined in IEC 60958-1:20—, Annex F to the switching procedure from one linear PCM audio mode to the other linear PCM audio mode: see Figure 6. This switching is involved by any changes in channel status bits 3 to 5, 32 to 35, 44 to 47, 49 to 60 and 64 to 165.
The interface should be idle during the transition, the null data is applied, and the channel status bit 1 is set to nonlinear PCM. The audio signal at the start and end portions of linear PCM data can fade in and out; this is effective for avoiding artefacts.Digital audio interface