Initial documentation for the multi-peer video routing system: - architecture.md covers graph model, transport protocol, relay design, and the Pi get-it-on-the-wire-first rationale - planning.md defines module build order and directory structure - conventions.md captures C11 code style, naming, error handling approach, and directory layout rules Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Planning
Approach
Build the system module by module in C11. Each module is a translation unit (.h + .c) with a clearly defined API. Modules are exercised by small driver programs in dev/ before anything depends on them. This keeps each unit independently testable and prevents architectural decisions from being made prematurely in code.
The final binary is a single configurable node program. That integration work comes after the modules are solid.
Directory Structure
video-setup/
modules/
common/ - shared definitions (error types, base types)
media_ctrl/ - Linux Media Controller API (topology, pad formats, links)
v4l2_ctrl/ - V4L2 camera controls (enumerate, get, set)
dev/
cli/ - exploratory CLI drivers, one per module
experiments/ - freeform experiments
tests/ - automated tests (later)
Makefile
architecture.md
planning.md
conventions.md
Module Order
Modules are listed in intended build order. Each depends only on modules above it.
| # | Module | Status | Notes |
|---|---|---|---|
| 1 | common |
not started | Error types, base definitions — no dependencies |
| 2 | media_ctrl |
not started | Media Controller API — device and topology enumeration, pad format config |
| 3 | v4l2_ctrl |
not started | V4L2 controls — enumerate, get, set camera parameters |
| 4 | transport |
not started | Encapsulated transport — header encode/decode, framed TCP read/write |
| 5 | frame_alloc |
not started | Per-frame allocation with bookkeeping (byte budget, ref counting) |
| 6 | relay |
not started | Input dispatch to output queues (low-latency and completeness modes) |
| 7 | ingest |
not started | MJPEG frame parser (two-pass EOI state machine, opaque stream → discrete frames) |
| 8 | archive |
not started | Write frames to disk, control messages to JSON log |
Dev CLI Drivers
Each module gets a corresponding CLI driver in dev/cli/ that exercises its API and serves as both an integration check and a useful development tool.
| Driver | Exercises | Notes |
|---|---|---|
media_ctrl_cli |
media_ctrl |
List media devices, show topology, configure pad formats |
v4l2_ctrl_cli |
v4l2_ctrl |
List controls, get/set values — lightweight v4l2-ctl equivalent |
transport_cli |
transport |
Send/receive framed messages, inspect headers |
Deferred Decisions
These are open questions tracked in architecture.md that do not need to be resolved before module work begins:
- Graph representation format
- Connection establishment model (push vs pull)
- Completeness queue drop policy (oldest vs newest, per-output config)
- Stream ID remapping across relay hops
- Transport for relay edges (TCP / UDP / shared memory)
- Node discovery mechanism
- Hard vs soft byte budget limits