Some knowledge accumulated about timestamping
=============================================

The meaning of the timestamps changed between v2.3.1 and v3.0.0, this document gives some guidance about the interaction between different settings.

The following table tries to summarise the differences.

+-----------------------------+----------------------------------------------+-------------------------------------+-----------------------------------------------+
| ODR-DabMux version          | Meaning of timestamp inside EDI              | ODR-ZMQ2EDI wait time w             | Offset that should be set in the mod          |
+=============================+==============================================+=====================================+===============================================+
| Up to and including v2.3.1  | t_frame = t_mux (No offset in mux available) | positive, meaning delay after t_mux | Something larger than w + mod processing time |
+-----------------------------+----------------------------------------------+-------------------------------------+-----------------------------------------------+
| Later than v2.3.1           | t_frame = t_tx = t_mux + tist_offset         | negative, meaning delay before t_tx | Something larger than mod processing time     |
+-----------------------------+----------------------------------------------+-------------------------------------+-----------------------------------------------+

The edilib tool decodes both EDI timestamp and MNSC, and can be used to verify both are identical.

Issues in ODR-DabMux v2.3.1
---------------------------

Running ODR-DabMux against the absolute timestamp firmware has uncovered a few issues:

 * At startup, the UTCO was not properly applied to the EDI seconds. This offset was 5 seconds (TAI-UTC offset - 32s, see EDI spec);
 * odr-zmq2edi did not compensate for UTCO, hiding the above issue;
 * ODR-DabMux needs a configurable offset;
 * (minor) MNSC and EDI timestamps did not use the same internal representation, making it difficult to prove that they encode the same value;
 * (minor) odr-zmq2edi swapped endianness when regenerating EDI from ETI (minor because only ODR-DabMod considers MNSC, and usually isn't used with EDI);

**Important** Do not combine odr-zmq2edi with odr-dabmux of a different version!