07 · Local helmet audio activation and first frame

Starting state

Sealed complete source roster, selected communication endpoint and explicit local start action.

Ordered events

1. UI → Service

   start requests local audio after endpoint verification

2. Service → Audio

   Acquire focus/communication route and open Oboe

3. Audio → Audio

   Process 480-sample capture blocks with APM and advisory VAD

4. Audio → Engine

   Two blocks produce Opus/SRTP and enqueue immutable media

5. Engine → Audio

   Authenticated remote ingress reaches jitter/decode/mix worker

Fields and messages

Local audioReady/interrupted/muted; source descriptor and RTP clock; device IDs/session IDs are local platform details.

Authorization and invariants

Remote control never starts microphone. Retired session output and wrong local epoch PCM are discarded; callbacks do no engine/codec work.

Timers

10-ms worker blocks, 20-ms packetization; jitter target initially 60 ms, adaptive 40–120; DTX startup at least 2 s.

Resource lifetime

Device route/APM session and PCM are local ephemeral state; source key and roster remain ride-scoped.

What the rider sees

Active/muted/speaking UI reflects local state and measurements, not assumed helmet function.

Failure branches

Unsupported/broken route stays unready or interrupted; focus loss stops local audio while permitted relay continues.

Resulting state

Capture/render active locally; first protected source packet reaches active links; remote decode is rendered through selected output.

Evidence boundary

Audio/processing/isolation host tests, JVM route policy and compiled headset instrumentation. Physical helmet correctness unqualified.