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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)	Prefer the source's own TA, fall back to inject. The server briefly waits (≈2 s after `VHEAD`) for the source's TA, decoded from either a valid MMDVM `DMRA` buffer or the embedded LC inside voice (FLCO 4–7). If found, it is passed through unchanged. If the source sent no TA within that window (e.g. a radio that does not support Talker Alias), ADN injects the configured template (embedded LC + `DMRA`). When the source is an OpenBridge system (which never carries TA), there is nothing to wait for, so ADN injects immediately at `VHEAD`.
`passthrough`	Relay the source's TA only (buffered `DMRA` and the source embedded LC, both untouched). Never inject the template.
`inject`	Always build TA from the configured template and alias data, overwriting the embedded LC and sending `DMRA` packets.

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).

The embedded LC of voice bursts B–E (dtype 1–4) is always rewritten with the destination group LC (re-encoded for the forwarded TGID, as legacy bridge.py does) — this is required for the receiving MMDVM to accept the voice; a stale embedded LC from the source TG causes packet loss. The Talker Alias is then overlaid on alternate superframes:

inject and the both no-source-TA fallback use the configured template.
passthrough and both with a source TA re-encode the source's own Talker Alias (decoded from its DMRA/embedded-voice blocks) and overlay that, so the radio's alias reaches the far side while the group LC stays correct for the new TG.

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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