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
The main layer is ETI-LI, it contains 24 ms 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 has a fixed packet size of 6144 Bytes, and fixed bitrate of 2 Mbit/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. Has a fixed bitrate of 2 Mbit/s (with all overhead) and Reed-Solomon forwarded error correction code 226 or 235 of 240 bytes. The 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.
- The Transport stream may be simulated by adding only 0x47 TS-sync byte at the beginning of each 188 byte packed, and the rest of it - is ETI-NA.
- May be other than pure DVB-S or DVB-S2 (for example DVB-GSE).
- May be EDI.
A list of (known) DAB streams over satellite can be found at https://github.com/piratfm/eti-tools#satellite-dab-feeds . All of them are not encrypted.
ETI conversion to http
To convert ETI-NI stream to HTTP (ready to icecast2) ni2http application from eti-tools may be used.