tr-plugin-avcf

Trunk Recorder plugin that captures analog voice recordings as self-contained .avcf files and/or publishes them over MQTT.

This is the analog companion to tr-plugin-dvcf. Where .dvcf captures raw codec frames for digital P25/DMR calls, .avcf wraps analog audio recordings with full call metadata in the same SSSP v2 container format.

Why

Standard trunk-recorder analog recordings are plain .wav files with no embedded metadata. To build an ASR training dataset, you need to correlate audio files with talkgroup labels, signal quality, speaker information, and other call-level data from external sources.

.avcf files are self-contained: one file per call, audio + metadata included. Upload a batch of .avcf files and you have a complete dataset.

Features

• File writing — saves .avcf sidecar files alongside audio recordings (same base name, .avcf extension)
• MQTT publishing — publishes analog call data as audio_avcf_base64 over MQTT
• Waveform agnostic — wraps WAV, FLAC, M4A, or OGG without transcoding
• Analog filtering — only processes analog calls by default (configurable)

File Format

.avcf = Analog Voice Capture Format. SSSP v2 binary container — see AVCF_SPEC.md for the full specification.

Each file contains:

1. CALL_START — call identification and timing
2. AUDIO_DATA — opaque audio blob with MIME content-type
3. CALL_METADATA — JSON with talkgroup labels, signal/noise, speaker list, etc.
4. CALL_END — call summary

Requirements

• Trunk Recorder v5.0+ with plugin API support
• Paho MQTT C++ (for MQTT publishing)
• Boost (already required by trunk-recorder)

Building

Builds as a user_plugins drop-in — no fork of trunk-recorder required.

# 1. Clone trunk-recorder
git clone https://github.com/TrunkRecorder/trunk-recorder.git
cd trunk-recorder

# 2. Drop this plugin into user_plugins/
mkdir -p user_plugins
git clone https://github.com/trunk-reporter/tr-plugin-avcf user_plugins/mqtt_avcf

# 3. Build with local plugins enabled
cmake -B build -DUSE_LOCAL_PLUGINS=ON
cmake --build build -j$(nproc)

# 4. Install
sudo cmake --install build

Dependencies

# Ubuntu/Debian
sudo apt-get install libpaho-mqtt3as-dev libpaho-mqttpp3-dev

Configuration

Add to your trunk-recorder config.json:

{
  "plugins": [
    {
      "name": "mqtt_avcf",
      "library": "libmqtt_avcf",
      "write_enabled": true,
      "mqtt_enabled": false,
      "analog_only": true,
      "broker": "tcp://localhost:1883",
      "topic": "trunk-recorder",
      "clientid": "avcf-handler",
      "username": "",
      "password": "",
      "qos": 0
    }
  ]
}

Option	Default	Description
write_enabled	true	Write .avcf sidecar files to disk
mqtt_enabled	false	Publish analog call data over MQTT
analog_only	true	Only process analog calls (skip digital)
broker	tcp://localhost:1883	MQTT broker URL
topic	trunk-recorder	MQTT topic prefix (publishes to {topic}/avcf)
clientid	avcf-handler	MQTT client ID
username	""	MQTT username (optional)
password	""	MQTT password (optional)
qos	0	MQTT QoS level

MQTT Message Format

When mqtt_enabled: true, the plugin publishes a JSON message on {topic}/avcf:

{
  "audio_avcf_base64": "<base64-encoded .avcf content>",
  "metadata": {
    "talkgroup": 9170,
    "talkgroup_tag": "Fire Dispatch",
    "talkgroup_group": "Fire",
    "freq": 855737500,
    "start_time": 1711234567,
    "stop_time": 1711234590,
    "call_length": 23,
    "signal": -42.5,
    "noise": -110.2,
    "emergency": false,
    "analog": true,
    "audio_type": "analog",
    "short_name": "butco",
    "filename": "9170-1711234567_855737500.wav",
    "srcList": [{"src": 1234567, "time": 1711234567, "pos": 0.0, "emergency": 0, "signal_system": "", "tag": ""}]
  }
}

Related Projects

• tr-plugin-dvcf — sibling plugin for digital P25/DMR codec frames
• IMBE-ASR — ASR model for digital calls (reads .dvcf files)
• tr-engine — backend that ingests MQTT and routes to ASR providers