# Architecture

## Layers

1. Capture

- Hardware: ATSC antennas -> HDHomeRun or Linux IPTV capture devices.
- Output: MPEG-TS or ATSC 3.0 streams.

2. Normalize

- Demux and normalize timestamps.
- Select program IDs and identify audio/video tracks.

3. Deterministic transcode

- Encode with a fixed profile (codec, GOP, bitrate, keyframe cadence).
- Emit fixed-duration chunks with stable ordering.
- Hash chunks to produce content identifiers.

4. MoQ publish

- Map each channel to a track namespace.
- Each chunk becomes a MoQ object in a group.
- Objects are named and addressed deterministically.

5. Relay mesh

- Relays cache objects and announce tracks.
- iroh provides programmable topology and peer routing.
- Multiple relays can serve identical objects.

6. Playback

- Desktop: Tauri app that subscribes to tracks.
- CLI: debugging, inspection, and headless clients.
- Web: static site that connects to a relay gateway.

## Roles

- Runner: owns capture + transcode + publish.
- Chopper: executes deterministic chunking profiles.
- Relay: stores and forwards MoQ objects.
- Manager: configures nodes and applies policy.
- Provisioner: bootstraps nodes and manages deployment.

## Determinism

- The same input with the same profile should yield identical chunks.
- Chunk hashes are the primitive for availability and de-duplication.
- Deterministic names allow relays to converge without coordination.

## Time synchronization

- Chunk boundaries are derived from PCR and, when available, broadcast UTC (ATSC STT / DVB TDT/TOT).
- Unsynced sources remain source-scoped until broadcast time is present.
- Discontinuities force a new chunk group boundary.