mikael-lovqvists-claude-agent
94ac152d55
- dev/web/ is the browser-side equivalent of dev/cli/ — a Node.js dev UI that speaks the binary protocol and exposes V4L2/topology inspection - Explicitly noted as blocked on transport+protocol being finalised - Distinguished from the future production dashboard - Directory structure updated to show serial/transport/protocol modules Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
98 lines
4.7 KiB
Markdown
98 lines
4.7 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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serial/ - little-endian binary serialization primitives
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transport/ - framed TCP stream, single-write send
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protocol/ - typed write_*/read_* message functions
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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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web/ - development web UI (Node.js/Express); browser-side equivalent
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of the CLI tools; depends on protocol being finalised
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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 Tools
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### CLI (`dev/cli/`)
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Each module gets a corresponding CLI driver 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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### Web UI (`dev/web/`)
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A Node.js/Express development web UI — the browser-side equivalent of the CLI tools. Connects to a running video node as a binary protocol peer and exposes its capabilities through a browser interface: V4L2 control inspection and adjustment, media topology view, stream state.
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**Prerequisite**: the `transport` and `protocol` modules must be finalised before `dev/web/` can be implemented — the web UI depends on a stable wire format and a `protocol.mjs` that mirrors the C protocol module.
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This is a development aid, not the production dashboard. The production dashboard (full stream configuration UI) is a later, separate project.
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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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