Content of the PES packet payload

Building a PES packet payload from a Dolby Digital Plus bitstream must meet certain conditions.

Note: These conditions are not applicable to audio-only elementary streams.
  • Each PES packet payload contains complete Dolby Digital Plus access units. One access unit consists of all of the parts of the bitstream required by the Dolby Digital Plus decoder to produce 1,536 samples of decoded audio for each audio channel present in the bitstream.
  • A Dolby Digital Plus access unit does not span multiple PES packet payloads.

    Multiple complete Dolby Digital Plus access units may be placed within a single PES packet payload, but fragmentation of Dolby Digital Plus access units within a payload, or across multiple payloads, is not permitted. Multiplexing multiple, complete Dolby Digital Plus access units into a single PES packet payload can increase the overall efficiency of the transport stream, and in some cases provides bit-rate savings for the overall transport stream.

  • Dolby Digital Plus frame bytes in the PES use big-endian format. (The first byte is 0x0B.)
  • Byte align the Dolby Digital Plus streams within the PES packet payload so that the initial eight bits of a Dolby Digital Plus frame reside in a single byte, placed at the start of the PES packet payload.
  • Frames are assembled in the same sequence in the PES packet payload as they occur in the Dolby Digital Plus stream.

To convert a Dolby Digital Plus stream to Dolby Digital, a decoder uses a correct set of six blocks of audio data to produce one Dolby Digital frame.

How Dolby Digital Plus data is structured within a PES packet payload depends on the configuration of the Dolby Digital Plus bitstream. This figure shows the construction of a PES packet payload that contains a single Dolby Digital Plus access unit consisting of six audio blocks.

Figure 1. PES packet payload with a single substream with six blocks per frame
PES packet payload with a single substream with six blocks per frame

The six audio blocks represent 1,536 samples of audio from a single substream (substream 0).

This figure shows a PES packet payload that contains a single access unit of Dolby Digital Plus audio consisting of four frames.

Figure 2. PES packet payload with two substreams with three blocks per frame
PES packet payload with two substreams with three blocks per frame

Each frame contains three audio blocks (denoted AB0 for substream 0 and AB1 for substream 1), each representing 256 samples of PCM audio from all channels in each substream.

This figure shows a PES packet payload that contains a single Dolby Digital Plus access unit consisting of six frames. Each frame contains one audio block, each representing 256 samples of PCM audio from every channel in the substream.

Figure 3. PES packet payload with a single substream with one block per frame
PES packet payload with a single substream with one block per frame