Raw AC-4 frame

Each raw AC-4 frame is composed of a table of contents and at least one substream.

The table of contents can be considered as the bitstream inventory where all important information for the overlaying system resides. Each table of contents contains the table-of-contents data and at least one presentation. An audio presentation informs the decoder about which parts of an AC-4 stream are intended to be played back simultaneously at a given point in time. Presentations consist of substream groups. Substream groups consist of one or more individual substreams. The substream group carries properties common to all substreams contained in the substream group. Substreams in one substream group are either all channel coded or all object coded. Substreams are decodable units that represent a specific channel configuration (mono, stereo, 5.1, or 7.1). All of the payload information (such as audio data and metadata) is stored in substreams.

The raw AC-4 frame structure is shown in the following figure, as described in ETSI TS 103 190-2.

Figure: Raw AC-4 frame structure

Raw AC-4 frame structure