83 lines
3.6 KiB
Markdown
83 lines
3.6 KiB
Markdown
# Architecture
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## Layers
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1. Capture
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- Hardware: ATSC antennas -> HDHomeRun or Linux IPTV capture devices.
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- Output: MPEG-TS or ATSC 3.0 streams.
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2. Normalize
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- Demux and normalize timestamps.
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- Select program IDs and identify audio/video tracks.
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3. Deterministic transcode
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- Encode with a fixed profile (codec, GOP, bitrate, keyframe cadence).
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- Emit fixed-duration chunks with stable ordering.
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- Hash chunks to produce content identifiers.
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4. MoQ publish
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- Map each channel to a track namespace.
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- Each chunk becomes a MoQ object in a group.
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- Objects are named and addressed deterministically.
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5. Settlement rails
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- Ethereum-compatible commitments mirror stream identity, manifests, and transport announcements.
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- Observation consensus is a separate rail on top of those commitments: a reality-derived
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`ObservationHeader` is hashed, witnessed, and finalized per `(stream, epoch)` slot.
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- The chain stores compact commitment pointers only; media bytes and full manifests remain on iroh,
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relays, and archive storage.
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- OP Stack is the current private-chain operator target, with `ecp-forge` as the head node for the
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first Sepolia-anchored testnet tranche.
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- Private-chain operation is a protocol extension, not a replacement for transport.
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6. Relay mesh
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- Relays cache objects and announce tracks.
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- iroh provides programmable topology and peer routing.
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- Multiple relays can serve identical objects.
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7. Playback
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- Desktop: Tauri app that subscribes to tracks.
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- CLI: debugging, inspection, and headless clients.
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- Web: static site that connects to a relay gateway.
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## Roles
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- Runner: owns capture + transcode + publish.
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- Chopper: executes deterministic chunking profiles.
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- Relay: stores and forwards MoQ objects.
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- Manager: configures nodes and applies policy.
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- Provisioner: bootstraps nodes and manages deployment.
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- Witness: attests to a reality-derived observation hash for a stream epoch.
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## Determinism
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- The same input with the same profile should yield identical chunks.
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- Chunk hashes are the primitive for availability and de-duplication.
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- Deterministic names allow relays to converge without coordination.
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- Observation consensus derives a second deterministic summary from the archive/manifests layer:
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`streamHash`, `epochHash`, `dataRoot`, and `locatorHash` become the on-chain observation header.
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- Local manifests keep BLAKE3 `manifest_id`s and `merkle+blake3` proofs, while the Ethereum rail
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adds Keccak ABI/data commitments and optional secp256k1 EIP-712 body signatures for settlement.
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- Discovery identity should prefer broadcast-scoped channel identity when available and only fall
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back to source-scoped IDs when the ingest path cannot yet prove a usable broadcast identity.
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- PAT-derived identity is accepted only when the stream exposes a single non-zero program; ambiguous
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multi-program TS inputs remain source-scoped to avoid accidental convergence on the wrong channel.
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- `ec-ts` parses ATSC PSIP at the table layer (`MGT`, `TVCT/CVCT`, `STT`, `RRT`, `EIT`, `ETT`),
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including `EIT` / `ETT` on the PIDs advertised by `MGT`.
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- Current discovery promotion uses `PAT` plus `VCT` fields; the rest of PSIP is parsed and preserved
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for inspection, validation, and future policy rather than guessed into the stream key.
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## Time synchronization
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- Chunk boundaries are derived from PCR and, when available, broadcast UTC (ATSC STT / DVB TDT/TOT).
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- ATSC STT is interpreted as GPS time plus offset correction, then converted to Unix time for chunk
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anchoring and diagnostics.
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- Unsynced sources remain source-scoped until broadcast time is present.
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- Discontinuities force a new chunk group boundary.
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