reproduced after the given delay. DTMF blocking modes are honoured at
the time when the DTMF events are reproduced.
* `DTMF-log-dest`
Contains a destination address and port for the DTMF logging feature. This
overrides the global destination from the `dtmf-log-dest` config option on
a per-call basis. Even if the global config option is unset, setting the
destination address/port via this option enables DTMF logging for this
call.
* `endpoint-learning`
Contains one of the strings `off`, `immediate`, `delayed` or `heuristic`. This tells rtpengine which endpoint learning algorithm to use and overrides the `endpoint-learning` configuration option. This option can also be put into the `flags` list using a prefix of `endpoint-learning-`.