Smartphone Projection Audio
Canonical Definition
Smartphone projection audio is the media, call, navigation, assistant, control, and display integration created when a compatible phone and vehicle host establish a wired or wireless CarPlay or Android Auto session. The session does not by itself identify the exact audio codec, sample rate, host mixing, volume group, DAC, or analog output path.
Projection Is Not Ordinary Bluetooth Media
Bluetooth may participate in discovery, pairing, control, calls, or fallback behavior, and Wi-Fi may carry a wireless projection data session. Wired projection uses a compatible USB data path. The complete audio route is controlled by the phone, application, projection framework, vehicle host, audio-focus policy, and downstream hardware.
Phone And Host Responsibilities
| Layer | Possible responsibility |
|---|---|
| phone and app | media session, decoding, app processing, metadata, calls, navigation, assistant |
| projection framework | approved interface, commands, templates, session and audio-context coordination |
| vehicle host | display, controls, audio focus, mixing, volume groups, conversion, vehicle functions |
| factory or aftermarket audio path | routing, DSP, DAC, line or speaker output, alerts, amplification |
The exact split is implementation-specific. Do not describe the host as a passive or “dumb” screen without evidence.
Android Auto Is Not Android Automotive OS
Android Auto projects a compatible phone experience to a vehicle host. Android Automotive OS runs on the vehicle's own hardware. An AAOS vehicle may have its own audio service, zones, focus policy, volume groups, power policy, and native media apps.
Contexts To Verify
- music and spoken media
- navigation guidance
- phone and communication audio
- voice assistant and speech recognition
- notifications, chimes, emergency and safety audio
- pause, resume, ducking, mute, fallback and restored source state
Verification
- Record phone, OS, app, host, firmware, wired or wireless mode, cable or radio state, and permissions.
- Measure media level, response, noise, latency, and channel map.
- Trigger navigation, assistant, call, notification, alert, and safety contexts separately.
- Test wired, wireless, ordinary Bluetooth, native head-unit, and fallback modes independently.
- Repeat after reconnect, app change, key cycle, and vehicle sleep.