Audio Service

The audio service is responsible for loading TTS and Audio plugins

All audio playback is handled by this service

Native playback

Usually playback is triggered by some originating bus message, eg "recognizer_loop:utterance", this message contains metadata that is used to determine if playback should happen.

message.context may contain a source and destination, playback is only triggered if a message destination is a native_source or if missing (considered a broadcast).

This separation of native sources allows remote clients such as an android app to interact with OVOS without the actual device where ovos-core is running repeating all TTS and music playback out loud

You can learn more about message targeting here

By default only utterances originating from the speech client and ovos cli are considered native

for legacy reasons the names for ovos cli and speech client are "debug_cli" and "audio" respectively

TTS

Two TTS plugins may be loaded at once, if the primary plugin fails for some reason the second plugin will be used.

This allows you to have a lower quality offline voice as fallback to account for internet outages, this ensures your device can always give you feedback

"tts": {
    "pulse_duck": false,
    "module": "ovos-tts-plugin-mimic2",
    "fallback_module": "ovos-tts-plugin-mimic"
},

Audio

You can enable additional Audio plugins and define the native sources described above under the "Audio" section of mycroft.conf

ovos-core uses OCP natively for media playback, you can learn more about OCP here

OCP will decide when to call the Audio service and what plugin to use, the main use case is for headless setups without a GUI

NOTE: mycroft-core has a "default-backend" config option, in ovos-core this option has been deprecated and is always OCP.

"Audio": {
    "native_sources": ["debug_cli", "audio"],

    "backends": {
      "OCP": {
        "type": "ovos_common_play",
        "active": true
      },
      "simple": {
        "type": "ovos_audio_simple",
        "active": true
      },
      "vlc": {
        "type": "ovos_vlc",
        "active": true
      }
    }
},