# DMF Studio — Implementation Plan

## Product Definition

**DMF Studio** is a node-based visual production platform for the Dynamic Media Facility architecture. It provides a canvas where users create, connect, and control containerized Media Functions that exchange live video via the MXL shared-memory layer.

## Technology Stack

| Component | Choice |
|---|---|
| Language | C++20 |
| Build | CMake 3.24+, vcpkg |
| MXL SDK | Git submodule (github.com/dmf-mxl/mxl) |
| WebSocket | libwebsockets |
| JSON | nlohmann/json |
| Logging | spdlog |
| GPU compute | Vulkan (headless render + compute shaders) |
| SDI I/O | Blackmagic DeckLink SDK |
| Color conversion | libyuv |
| JPEG encoding | libjpeg-turbo |
| Testing | Catch2 |
| Frontend (phase 4) | Vue 3 + Vue Flow + Vite + Pinia |

## Architecture Principles

1. **Separate processes per node** — crash isolation, true DMF model
2. **MXL is the ONLY data path between nodes** — zero-copy shared memory
3. **Engine owns the graph, nodes own the media** — clean separation
4. **Engine generates flow IDs, nodes create MXL readers/writers** — centralized routing
5. **WebSocket control per node** — NMOS IS-12 aligned, bidirectional
6. **All nodes use `libdmf-node` skeleton** — consistent lifecycle
7. **Node binary = 1 C++ class + 1 main.cpp** — minimal per-node code
8. **Vulkan for GPU, CPU fallback available** — GPU-accelerated but not GPU-required
9. **Video only for MVP** — audio deferred
10. **Backend first, frontend last** — validate with curl + minimal HTML before building UI

## Project Structure

```
dmf-studio/
├── CMakeLists.txt
├── vcpkg.json
├── vcpkg-configuration.json
│
├── extern/
│   └── mxl/                              # git submodule
│
├── libs/
│   ├── dmf-node/                         # Node skeleton library (static)
│   │   ├── CMakeLists.txt
│   │   ├── include/dmf-node/
│   │   │   ├── node.hpp                  # Abstract Node interface
│   │   │   ├── port.hpp                  # PortDef, PortDirection, MediaType
│   │   │   ├── node_runner.hpp           # CLI, MXL init, control WS, main loop
│   │   │   ├── control_server.hpp        # WS server per-node
│   │   │   └── types.hpp                 # NodeId, PortId, FlowId aliases
│   │   └── src/
│   │       ├── node_runner.cpp
│   │       └── control_server.cpp
│   │
│   └── dmf-engine/                       # Engine library (static)
│       ├── CMakeLists.txt
│       ├── include/dmf-engine/
│       │   ├── graph.hpp                 # Graph model: nodes, edges
│       │   ├── flow_manager.hpp          # Flow UUID gen, NMOS flow defs
│       │   ├── process_manager.hpp       # Spawn/monitor/kill node processes
│       │   ├── api_server.hpp            # REST + WS to browser
│       │   └── types.hpp                 # Graph-level types
│       └── src/
│           ├── graph.cpp
│           ├── flow_manager.cpp
│           ├── process_manager.cpp
│           └── api_server.cpp
│
├── nodes/
│   ├── passthrough/
│   │   ├── CMakeLists.txt
│   │   └── src/
│   │       ├── main.cpp
│   │       ├── passthrough_node.hpp
│   │       └── passthrough_node.cpp
│   │
│   ├── test-source/
│   │   ├── CMakeLists.txt
│   │   └── src/
│   │       ├── main.cpp
│   │       ├── test_source_node.hpp
│   │       ├── test_source_node.cpp
│   │       ├── vulkan_context.hpp
│   │       ├── vulkan_context.cpp
│   │       ├── vulkan_renderer.hpp
│   │       ├── vulkan_renderer.cpp
│   │       └── shaders/
│   │           ├── pattern.vert
│   │           ├── pattern_bars.frag
│   │           ├── pattern_ramp.frag
│   │           ├── pattern_solid.frag
│   │           └── rgb_to_v210.comp
│   │
│   ├── decklink-in/
│   │   ├── CMakeLists.txt
│   │   └── src/
│   │       ├── main.cpp
│   │       ├── decklink_in_node.hpp
│   │       └── decklink_in_node.cpp
│   │
│   ├── decklink-out/
│   │   ├── CMakeLists.txt
│   │   └── src/
│   │       ├── main.cpp
│   │       ├── decklink_out_node.hpp
│   │       └── decklink_out_node.cpp
│   │
│   ├── preview/
│   │   ├── CMakeLists.txt
│   │   └── src/
│   │       ├── main.cpp
│   │       ├── preview_node.hpp
│   │       └── preview_node.cpp
│   │
│   └── mixer/
│       ├── CMakeLists.txt
│       └── src/
│           ├── main.cpp
│           ├── mixer_node.hpp
│           └── mixer_node.cpp
│
├── engine/
│   ├── CMakeLists.txt
│   └── src/
│       └── main.cpp
│
├── web/                                   # Phase 4 — Vue 3 frontend
│   ├── package.json
│   ├── vite.config.ts
│   ├── tsconfig.json
│   └── src/
│       ├── App.vue
│       ├── main.ts
│       ├── api/
│       │   ├── rest.ts
│       │   └── websocket.ts
│       ├── stores/
│       │   ├── graph.ts
│       │   └── connection.ts
│       ├── canvas/
│       │   ├── StudioCanvas.vue
│       │   ├── nodes/
│       │   │   ├── SourceNode.vue
│       │   │   ├── ProcessorNode.vue
│       │   │   ├── OutputNode.vue
│       │   │   └── NodeThumbnail.vue
│       │   └── edges/
│       │       └── FlowEdge.vue
│       ├── panels/
│       │   ├── NodeProperties.vue
│       │   ├── Toolbar.vue
│       │   └── StatusBar.vue
│       └── templates/
│           └── templateLoader.ts
│
├── templates/
│   ├── loopback.json
│   ├── sdi_monitor.json
│   ├── sdi_pass.json
│   └── simple_switcher.json
│
├── docker/
│   ├── Dockerfile.engine
│   ├── Dockerfile.node.test-source
│   ├── Dockerfile.node.decklink-in
│   ├── Dockerfile.node.decklink-out
│   ├── Dockerfile.node.preview
│   ├── Dockerfile.node.passthrough
│   └── docker-compose.yaml
│
└── tests/
    ├── CMakeLists.txt
    ├── test_graph.cpp
    ├── test_flow_manager.cpp
    └── test_control_protocol.cpp
```

## Node Interface

```cpp
class Node {
public:
    virtual ~Node() = default;
    virtual std::string type() const = 0;
    virtual std::vector<PortDef> input_ports() const = 0;
    virtual std::vector<PortDef> output_ports() const = 0;
    virtual void configure(const nlohmann::json& params) = 0;
    virtual void on_add_writer(const std::string& port_id, mxlFlowWriter writer) = 0;
    virtual void on_add_reader(const std::string& port_id, mxlFlowReader reader) = 0;
    virtual void on_remove_writer(const std::string& port_id) = 0;
    virtual void on_remove_reader(const std::string& port_id) = 0;
    virtual void process() = 0;
    virtual nlohmann::json status() const = 0;
};
```

## Control Protocol (Engine ↔ Node via WebSocket)

Engine → Node:

```json
{ "cmd": "add_writer", "flow_id": "uuid", "flow_def": { ... } }
{ "cmd": "add_reader", "flow_id": "uuid" }
{ "cmd": "remove_writer", "port_id": "out_0" }
{ "cmd": "remove_reader", "port_id": "in_0" }
{ "cmd": "configure", "params": { ... } }
{ "cmd": "shutdown" }
```

Node → Engine:

```json
{ "event": "ready", "type": "test_source", "ports": { ... } }
{ "event": "flow_status", "port_id": "out_0", "writing": true, "fps": 50 }
{ "event": "error", "message": "..." }
{ "event": "grain_stats", "port_id": "out_0", "grains_written": 1234, "latency_us": 120 }
```

## Flow Connection Sequence

```
User draws edge in UI (or REST API call):
  1. Engine generates flow UUID + NMOS flow definition
  2. Engine → Node A: { "cmd": "add_writer", "flow_id": ..., "flow_def": ... }
  3. Node A creates mxlFlowWriter, starts writing grains
  4. Node A → Engine: { "event": "flow_status", "writing": true }
  5. Engine → Node B: { "cmd": "add_reader", "flow_id": ... }
  6. Node B creates mxlFlowReader, starts reading grains
  7. Node B → Engine: { "event": "flow_status", "reading": true }

User removes edge:
  1. Engine → Node B: { "cmd": "remove_reader", "port_id": ... }
  2. Node B destroys mxlFlowReader
  3. Engine → Node A: { "cmd": "remove_writer", "port_id": ... }
  4. Node A destroys mxlFlowWriter
```

## Engine REST API

```
GET    /api/graph                       # Current node graph
POST   /api/graph/nodes                 # Add node { type, id? }
DELETE /api/graph/nodes/:id             # Remove node
POST   /api/graph/edges                 # Connect { from_node:from_port, to_node:to_port }
DELETE /api/graph/edges/:id             # Disconnect
PUT    /api/graph/nodes/:id             # Configure node
POST   /api/graph/start                 # Start all node processes + create flows
POST   /api/graph/stop                  # Stop all
GET    /api/templates                   # List templates
POST   /api/templates/:name/load        # Load template as graph
GET    /api/nodes/types                 # List available node types
```

## Node Designs

### Test Source (Vulkan)

- Headless Vulkan: render 2 fullscreen triangles with pattern fragment shader → RGBA8 image
- Compute shader `rgb_to_v210.comp`: RGBA8 → BT.709 YCbCr → 4:2:2 downsample → V210 packing
- vkMapMemory → memcpy to MXL grain → commit
- Patterns: SMPTE bars, luma ramp, solid color
- Frame pacing to target 50fps
- 1 output port: `video_out` (V210)

### Passthrough

- Read 1 MXL grain → memcpy → write 1 MXL grain
- 1 input: `video_in`, 1 output: `video_out`
- Hello-world node for validating the pipeline

### Preview

- Read V210 MXL grain → libyuv convert to RGBA → downsample to 480×270 → libjpeg-turbo → JPEG
- Push JPEG frames to subscribed WS clients (throttled to ~15fps)
- 1 input: `video_in`

### DeckLink In

- IDeckLinkInputCallback::VideoInputFrameArrived → GetBytes (V210) → memcpy to MXL grain → commit
- V210 native match = straight copy, no conversion
- 1 output: `video_out`
- Config: device index, connection type

### DeckLink Out

- IDeckLinkOutputCallback::ScheduledFrameCompleted → read MXL grain → memcpy to DeckLink buffer → schedule frame
- 1 input: `video_in`
- Config: device index, connection type

### Mixer

- 2 inputs: `video_a`, `video_b` (V210) → 1 output: `program` (V210)
- Cut: select active input
- Dissolve: blend A×(1-t) + B×t over N frames
- V210 blending: unpack 10-bit → linear blend → repack
- Config: active_input, transition_type, transition_duration_frames

## Implementation Phases

### Phase 1: Framework + Passthrough (Week 1-2)

**Goal: Two processes exchanging video via MXL, controlled by engine**

| Step | Task | Test |
|---|---|---|
| 1.1 | Repo init, CMake top-level, vcpkg, MXL submodule | Build succeeds |
| 1.2 | Verify MXL SDK: `mxl-gst-testsrc` + `mxl-gst-sink` work | Video displays |
| 1.3 | Build `libdmf-node`: node.hpp, port.hpp, control_server, node_runner | Unit tests pass |
| 1.4 | Build `passthrough` node binary | Starts, connects to MXL |
| 1.5 | Build `libdmf-engine`: graph, flow_manager, process_manager, api_server | Unit tests pass |
| 1.6 | Build engine binary with minimal REST | `curl` works |
| 1.7 | Integration: engine starts 2 passthrough processes, creates flow between them | Frames flow A→B |

**Testing method**: curl + mxl-gst-testsrc/sink as external I/O

### Phase 2: Test Source + Preview (Week 3-4)

**Goal: GPU-generated color bars visible in browser**

| Step | Task | Test |
|---|---|---|
| 2.1 | Vulkan headless context (VkDevice, queues, command pool) | Device created |
| 2.2 | Pattern fragment shaders (bars, ramp, solid) + fullscreen vert | Render to RGBA8 |
| 2.3 | `rgb_to_v210.comp` compute shader | V210 output verified |
| 2.4 | `test-source` node: render → compute → MXL write | MXL flow active |
| 2.5 | `preview` node: MXL read → libyuv → JPEG → WS | Browser sees frames |
| 2.6 | Engine integration: test-source → preview | curl starts graph, browser shows bars |

**Testing method**: curl to start graph, open browser to preview WS endpoint, see live color bars

### Phase 3: DeckLink I/O (Week 5-6)

**Goal: Real SDI signal flowing through DMF**

| Step | Task | Test |
|---|---|---|
| 3.1 | `decklink-in` node: DeckLink callback → MXL writer | SDI camera → MXL flow |
| 3.2 | `decklink-out` node: MXL reader → DeckLink playback | MXL flow → SDI monitor |
| 3.3 | Templates: sdi_monitor, sdi_loopback, test_output | Load and run via curl |
| 3.4 | Full pipeline: SDI in → preview → browser | Camera visible in browser |

**Testing method**: curl to start graph, real SDI camera + monitor

### Phase 4: Frontend (Week 7-8)

**Goal: Visual graph editor on DMF TV**

| Step | Task | Test |
|---|---|---|
| 4.1 | Vue 3 + Vite project setup, Vue Flow integration | Dev server runs |
| 4.2 | Pinia stores: graph model, WS connection | State management works |
| 4.3 | StudioCanvas: drag-add nodes, draw edges, delete | Graph editing works |
| 4.4 | Custom node components: type icon, name, status, live thumbnail | Nodes render |
| 4.5 | FlowEdge: color-coded by flow status | Edges render |
| 4.6 | NodeProperties panel: dynamic config from node schema | Config changes work |
| 4.7 | Toolbar: New/Load/Save/Run/Stop + template menu | Full workflow works |
| 4.8 | StatusBar: node count, flow count, running state | Status updates live |
| 4.9 | Test on DMF TV browser | Everything renders and works |

**Testing method**: Full end-to-end — build graph in UI, run, see live video

### Phase 5: Mixer Node (Week 9-10)

**Goal: DMF Studio is a production tool**

| Step | Task | Test |
|---|---|---|
| 5.1 | `mixer` node: 2-in, 1-out, cut + dissolve | Cut/dissolve work via curl |
| 5.2 | Mixer control panel in Vue: PGM/PVW buses, CUT, AUTO TRANS, T-bar | UI controls work |
| 5.3 | Template: Simple Switcher (2 sources → mixer → preview + SDI out) | Full production workflow |
| 5.4 | Polish, bug fixes, edge cases | Stable demo |

## vcpkg.json Dependencies

```json
{
  "name": "dmf-studio",
  "version": "0.1.0",
  "dependencies": [
    "libwebsockets",
    "nlohmann-json",
    "spdlog",
    "fmt",
    "libyuv",
    "libjpeg-turbo",
    "catch2"
  ]
}
```

Vulkan: `find_package(Vulkan)` — system install, not vcpkg.
DeckLink SDK: vendor headers linked manually, not in vcpkg.

## Key Risks and Mitigations

| Risk | Mitigation |
|---|---|
| MXL SDK API changes | Pin submodule to v1.0.1 tag, test before upgrading |
| V210 compute shader correctness | Validate against known reference frames, compare with libyuv output |
| DeckLink SDK availability on dev machine | Develop without hardware using test-source; DeckLink nodes only need testing on machines with cards |
| Single-process engine becomes bottleneck | Engine never touches media data; it only manages metadata and process lifecycle |
| WebSocket control latency | All control is localhost; sub-ms latency. Remote control is future work |
| Vulkan driver compatibility | Start with standard Vulkan 1.2; no extensions required for headless compute |