mikael-lovqvists-claude-agent
ea3fcc2c0f
architecture.md: - Web interface connects as a first-class binary protocol peer; no JSON bridge in C; DataView in JS maps directly to get_u32 etc. - Future preprocessor section: protocol schema defined once, emits both C (put/get, write_*/read_*) and ESM JS (DataView encode/decode); same tool as planned for error location codes planning.md: - Add web node (entry #11) to module order - Add Future: Protocol Preprocessor section above Deferred Decisions Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
83 lines
3.7 KiB
Markdown
83 lines
3.7 KiB
Markdown
# Planning
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## Approach
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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.
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The final binary is a single configurable node program. That integration work comes after the modules are solid.
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---
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## Directory Structure
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```
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video-setup/
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src/
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modules/
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common/ - shared definitions (error types, base types)
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media_ctrl/ - Linux Media Controller API (topology, pad formats, links)
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v4l2_ctrl/ - V4L2 camera controls (enumerate, get, set)
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node/ - video node entry point and top-level integration (later)
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include/ - public headers
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dev/
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cli/ - exploratory CLI drivers, one per module
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experiments/ - freeform experiments
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tests/ - automated tests (later)
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Makefile
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architecture.md
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planning.md
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conventions.md
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```
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---
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## Module Order
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Modules are listed in intended build order. Each depends only on modules above it.
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| # | Module | Status | Notes |
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|---|---|---|---|
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| 1 | `common` | done | Error types, base definitions — no dependencies |
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| 2 | `media_ctrl` | done | Media Controller API — device and topology enumeration, pad format config |
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| 3 | `v4l2_ctrl` | done | V4L2 controls — enumerate, get, set camera parameters |
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| 4 | `serial` | not started | `put`/`get` primitives for little-endian binary serialization into byte buffers |
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| 5 | `transport` | not started | Encapsulated transport — frame header, TCP stream abstraction, single-write send |
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| 6 | `protocol` | not started | Typed `write_*`/`read_*` functions for all message types; builds on serial + transport |
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| 7 | `frame_alloc` | not started | Per-frame allocation with bookkeeping (byte budget, ref counting) |
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| 8 | `relay` | not started | Input dispatch to output queues (low-latency and completeness modes) |
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| 9 | `ingest` | not started | MJPEG frame parser (two-pass EOI state machine, opaque stream → discrete frames) |
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| 10 | `archive` | not started | Write frames to disk, control messages to binary log |
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| 11 | `web node` | not started | Node.js/Express peer — speaks binary protocol on socket side, HTTP/WebSocket to browser; `protocol.mjs` mirrors C protocol module |
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---
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## Dev CLI Drivers
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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.
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| Driver | Exercises | Notes |
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|---|---|---|
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| `media_ctrl_cli` | `media_ctrl` | List media devices, show topology, configure pad formats |
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| `v4l2_ctrl_cli` | `v4l2_ctrl` | List controls, get/set values — lightweight `v4l2-ctl` equivalent |
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| `transport_cli` | `transport` | Send/receive framed messages, inspect headers |
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---
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## Future: Protocol Preprocessor
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The C `protocol` module and JavaScript `protocol.mjs` will eventually be generated from a single schema by a future preprocessor. This eliminates drift between the two implementations. The preprocessor also handles error location codes (see `common/error`). Neither the schema format nor the preprocessor tool exists yet — the hand-written implementations are the interim state.
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---
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## Deferred Decisions
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These are open questions tracked in `architecture.md` that do not need to be resolved before module work begins:
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- Graph representation format
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- Connection establishment model (push vs pull)
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- Completeness queue drop policy (oldest vs newest, per-output config)
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- Stream ID remapping across relay hops
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- Transport for relay edges (TCP / UDP / shared memory)
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- Node discovery mechanism
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- Hard vs soft byte budget limits
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