Ensemble Transport Interface

The Ensemble Transport Interface (ETI) is a standardised output stream from a DAB/DAB+/T-DMB multiplexer. It consists of a 2Mbit/s synchronous stream. Network adaptation is defined for G.703 lines (E1) that is the typical physical interface used between the multiplexer and DAB OFDM modulator. The ETI stream can also be recorded to a file for capture and replay.

Recently WorldDMB developped an adaptation of ETI for IP, called EDI (Encapsulated DAB Interface).

ETI is standardized at ETSI: EN 300 799

ETI Layers

The main layer is ETI-LI, it contains 24ms frame of DAB multiplex data. This logical frame may be incapsulated into:

• ETI-NI (G.703) - The simplest transport interface (just added sync words at the beginning and padding at the end). It have fixed packet size of 6144 bytes, and fixed bitrate of 2Mbit/s.
• ETI-NI (V.11) - Same as G.703 but with variable frame size and bitrate.
• ETI-NA (G.704) - More complex incapsulation method for E1/T1 interface. Have fixed bitrate of 2Mbit/s (with all overhead). Have Reed-Solomon forwarded error correction code 226 or 235 of 240 bytes. Packet size is fixed to 5592 or 5376 bytes (depending of error correction mode). This layer is used for satellite distribution of DAB stream.

ETI satellite distribution

Some provides are distributing ETI streams by incapsulation of it into MPEG-TS. That streams may also be:

• Not bit-aligned to transport stream.
• May be inverted.

Tools

• CRC ETI Streamer: tool developped by CRC for replaying ETI file on an E1/G.703 card
• ts2eti and eti_na2ni: eti extractor from MPEG-TS and NA-to-NI converter.