ANSI SCTE 243-4:2018 pdf free download – Next Generation Audio Carriage for Cable Systems: Part 4 – DTS-UHD Audio Carriage Constraints
6.2.3.7 StreamIndex
When a given Audio Program is delivered using multiple streams, StreamIndex is the index used to indicate stream priority for prioritizing mixing metadata. The main stream shall have StreamIndex=0, while auxiliary streams shall have StreamIndex values in the range of 1-7. If the Audio Program is delivered in a single stream, StreamIndex shall be 0. The value of StreamIndex shall correspond to the value of StreamID carried in the DTS-UHD BroadcastChunk as defined in SCTE DVS 242-4[3].
6.2.3.8 reserved_bits
These bits serve to byte align some parameters in the descriptor and may be defined for use in future specifications. For the purposes of this specification, all reserved_bits shall be set to 0 and ignored by the receiver.
6.2.3.9 ExtendedPayloadBytes
The number of bytes, ByteCount, is determined by parsing the parameters defined here and comparing the number of bytes remaining to be parsed based on descriptor_length. If ExtendedPayloadBytes exist, receivers built to this this specification shall ignore this data.
6.2.4 LongDescriptor Parameters
The parameters described in this section are conditionally present if LongDescriptor [Table 1] is set to 1.
6.2.4.1 NumPresentationsCode This field represents the number of audio presentations encoded within DTS-UHD elementary stream. The valid range of the bitstream parameter m_ucNumAudioPres defined in TS 103 491 [7] is from 1 to 32. The relationship between NumPresentationsCode and NumPresentations shall be as follows: NumPresentations = m_ucNumAudioPres = NumPresentationsCode + 1
6.2.4.2 ChannelMask A bit mask that indicates the channel layout encoded in the default presentation of the DTS-UHD bitstream according to the bit-to-channel-label mapping described in Table 4. Note that the ChannelMask table is derived from Channel Bitmask defined in TS 103 584 [8].
When RepresentationType has a value of 0, ChannelMask shall be set to a value that directly corresponds to the encoded channels. When RepresentationType has a value of 1 or 2, ChannelMask shall be set to a value that corresponds to the layout of the encoded channels into which higher spatial resolution components have been rendered (i.e. the corresponding channels that have been delivered to the audio compression engine). For example, LtRt material would have a ChannelMask of 0x00000006, representing the two channels of encoded audio content that may be presented at a higher spatial resolution on, for example, a 5.1-channel system. When RepresentationType is equal to 3, ChannelMask shall be set to 0x00000006, indicating Left and Right channels are active. When RepresentationType is greater than 3, ChannelMask shall be set to 0x00000000, indicating that the audio presentation is channel layout agnostic.