IEC 61937-15-2021 pdf free.Digital audio – Interface for non-linear PCM encoded audio bitstreams applying IEC 60958 – Part 15: Non-linear PCM bit streams according to Auro-Cx format.
4 Mapping of the audio bit stream on to IEC 61937-1
4.1 General
The coding of the bit stream and data-burst is in accordance with IEC 61937-1 and IEC 61937-2.
4.2 Auro-Cx burst-info
The 16-bit burst-info contains information about the data that will be found in the data-burst (see Table 2).
The burst-info (Pc) bits 0-4 signal the data-type used for the transmission. For Auro-Cx, the data-type is set to 26.
Pc bits 5-6 indicate the Auro-Cx bit stream mode. The repetition periods of data-bursts in
IEC 60958 frames shall be derived from the data-type-dependent information specified in
Table 4, Table 9, Table 14 and Table 19.
5 Format of Auro-Cx data-bursts
5.1 General
This clause specifies the Auro-Cx data-burst. Specific properties such as reference points, repetition period, the method of filling stream gaps and decoding latency are specified.
To establish synchronisation between the picture and decoded audio, the transmitter should use the latency indicated for the data-type to schedule data-bursts as necessary.
5.2 Pause data-burst
The Pause data-burst for Auro-Cx is given in Table 3.
If regular audio data-bursts are not being transmitted because of a pause condition, for example, it is recommended that Pause data-bursts are used to fill the stream gaps in the ACX bit stream, as described in IEC 61937-1. The Pause data-bursts should be transmitted with a repetition rate period in accordance with Table 3, except when other repetition periods are necessary to fill the precise stream gap length, which may not be a multiple of 3 PEC 60958 frames, or to meet the requirement on burst spacing (refer to IEC 61937-1).
When a stream gap in an ACX stream is filled by a sequence of Pause data-bursts, the Pa of the first Pause data-burst shall be located one data-burst repetition period following the Pa of the previous Auro-Cx block. It is recommended that the sequence(s) of Pause data-bursts, which fill the stream gap, should continue from this point up to (as close as possible considering the total IEC 60958 frame length of the Pause data-burst) the Pa of the first ACX data-burst that follows the stream gap.
The gap length parameter contained in the Pause data-burst is intended to be interpreted by the Auro-Cx decoder as an indication of the number of decoded PCM samples that are missing (due to the resulting audio gap).
5.3 Audio data-bursts
5.3.1 ACX data-burst
An ACX bit stream consists of a sequence of Auro-Cx blocks. The ACX data-burst is headed with a burst-preamble, followed by the burst-payload and stuffing. The structure of the ACX data-burst is shown in Figure 1. The data-type of an ACX data-burst is 26 and the subdata-type is 0. When transmitting Auro-Cx data, the transmitter needs to set both the data-type and subdata-type correctly. The receiving device shall then use both values to make sure that the content of the data-burst is identified as Auro-Cx.IEC 61937-15 pdf download.