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Talker Alias (DMR)

DMR Talker Alias (ETSI TS 102 361-2, 2016) carries a short alphanumeric label in the voice stream. On the Homebrew Protocol (HBP) it appears as separate DMRA UDP packets (15 bytes each, up to four per transmission).

This is not the same as subscriber ID aliases in subscriber_ids.json used for logs and the monitor UI. Talker Alias is embedded signaling intended for radio displays (OLED, Hytera/MD380tools, etc.).

How ADN handles Talker Alias

When enabled on a MASTER system, the server can:

Mode	Behaviour
`both` (default)	Pass through TA from the source hotspot/radio when all four `DMRA` blocks were received; otherwise inject from `subscriber_ids` + template.
`passthrough`	Relay buffered `DMRA` only.
`inject`	Always build TA from the configured template and alias data.

On bridge forward at voice header (VHEAD), the server sends four DMRA packets to each HBP target (MASTER peers or PEER upstream) once per stream, then forwards DMRD as usual.

MMDVMHost / DMRGateway (Pi-Star, WPSD): stock MMDVMHost does not consume standalone downlink DMRA UDP; it decodes Talker Alias from embedded LC inside DMRD voice (FLCO 4–7). When TA is enabled, ADN injects TA into the embedded LC of voice bursts B–E (dtype 1–4) on bridge forward to HBP targets, in addition to optional standalone DMRA packets for clients that support them.

On the same MASTER, when REPEAT copies group voice to other logged-in hotspots, the server also sends those four DMRA packets on VHEAD (excluding the transmitting peer). Bridge forwarding to the same system shares the same once-per-stream dedupe, so TA is not sent twice.

Not supported: OpenBridge legs (no standard DMRA on OBP/DMRE wire). Legacy ADN never implemented TA beyond debug logging.

Configuration

Under GLOBAL (optional per-system override with the same keys):

GLOBAL:
  TALKER_ALIAS: false
  TALKER_ALIAS_MODE: both
  TALKER_ALIAS_FORMAT: "{callsign} {fname}"

Key	Meaning
TALKER_ALIAS	Master switch (`false` by default).
TALKER_ALIAS_MODE	`both`, `passthrough`, or `inject`. Default `both` if omitted.
TALKER_ALIAS_FORMAT	Python format string; fields: `{callsign}`, `{fname}`, `{surname}`, `{id}`.

Maximum string length is 29 characters (ETSI / MMDVMHost). This limit is fixed in code and is not configurable, to avoid incompatible payloads on radios and hotspots.

Subscriber JSON may include fname, surname, or a dedicated talker_alias field per record.

HBP `DMRA` wire format

Offset	Field
0–3	`DMRA`
4–6	Source DMR ID (3 bytes, big-endian)
7	Block index 0–3
8–14	7 payload bytes

Encoding uses UTF-8 format (format 2), matching MMDVMHost DMRTA.cpp.

Embedded TA in DMRD voice alternates superframes: one cycle (bursts B–E) with the normal group embedded LC, the next with a TA block (FLCO 4–7), repeating until the stream ends.

Pi-Star / MMDVM operator settings

For TA to reach the local RF radio:

Setting	Recommendation
DMR DumpTAData	`1` (on, Pi-Star default): write embedded Talker Alias to the MMDVM log — required for Pi-Star dashboard / log-based tools to show TA; with `0` nothing appears there. This does not block TA on RF.
DMR EmbeddedLCOnly	`off` (default). If `on`, Talker Alias from the network is disabled.

Pi-Star’s web dashboard does not show TA; use the radio OLED, MD380tools, or tools such as pistar-lastqso.

Radio compatibility: Hytera PD6/7/9 and MD380tools firmware generally work. Many Motorola radios do not support TA; some older firmware may show audio issues when TA is present.

The adn-monitor proxy already forwards DMRA to the master unchanged.

Limitations and follow-up work

Topic	Status
TA on OpenBridge targets	Not available (no `DMRA` on standard OBP wire).
Monitor dashboard live TA column	Separate work (monitor uses DB aliases, not live `DMRA`).
Unrelated `RuntimeError` in bridge iteration	Tracked as a separate fix.

References

ETSI TS 102 361-2 (Talker Alias format)
MMDVMHost DMRTA.cpp / DMRNetwork.cpp (writeTalkerAlias)

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