Update dataset structure with detailed file format documentation

README.md

@@ -67,30 +67,62 @@ Each participant's data is packaged as a zip file: `CUHK-S_userN-userN.zip`
 
 ```
 CUHK-S/
-├── HAR/                    # Human Action Recognition (per-action organized)
-│   ├── data/
-│   │   ├── depth_color/
-│   │   ├── ir/
-│   │   ├── thermal/
-│   │   ├── imu/
-│   │   ├── radar/
-│   │   └── skeleton/
-│   └── GT/                 # Ground truth annotations
-├── HARn/                   # Human Action Reasoning (per-modality organized)
-│   ├── data/
-│   └── GT/
-├── HAU/                    # Human Action Understanding (per-modality organized)
-│   ├── data/
-│   └── GT/
-└── source_data/            # Raw source data
-    ├── data/
-    └── GT/
+├── HAR/                          # Human Action Recognition task
+│   └── data/
+│       ├── Depth_Color/          # Colorized depth frames (.png)
+│       ├── IR/                   # Infrared frames (.png)
+│       ├── Thermal/              # Thermal imaging frames (.png)
+│       ├── Skeleton/             # Skeleton pose data
+│       │   └── {action}/{user}/{session}/
+│       │       ├── predictions/  # Keypoint JSON (.json) + overlay images (.jpg)
+│       │       └── visualizations/
+│       ├── IMU/                  # IMU sensor data (CSV)
+│       │   └── {action}/{user}/{session}/
+│       │       ├── up(LA+RA+C).csv   # Upper-body IMU (Left Arm + Right Arm + Chest)
+│       │       └── down(LL+RL).csv   # Lower-body IMU (Left Leg + Right Leg)
+│       └── Radar/                # mmWave radar data (CSV)
+│           └── {action}/{user}/{session}/
+│               └── radar_output_T{timestamp}.csv
+│
+├── HAU/                          # Human Action Understanding task
+│   └── data/
+│       ├── Depth/                # Visual modality clips as .mp4 video
+│       ├── IR/
+│       └── Thermal/
+│           └── {user}/{session}/
+│               └── {Modality}.mp4
+│
+├── HARn/                         # Human Action next-step Reasoning task
+│   └── data/
+│       ├── Depth/                # Video clips as .mp4
+│       └── IR/
+│           └── {action}/{user}/{session}/
+│               └── Depth.mp4
+│
+└── source_data/                  # Raw source frames (with timestamps)
+    └── data/
+        ├── Depth_Color/          # Timestamped raw frames (.png)
+        ├── IR/
+        ├── Thermal/
+        ├── Skeleton/
+        ├── IMU/
+        └── Radar/
+            └── {user}/{session}/
+                └── {Modality}_{timestamp}_{frameId}.png
 ```
 
-- **HAR**: Singular well-defined actions for traditional classification tasks
-- **HAU**: Sequential actions for temporal and contextual understanding
-- **HARn**: Sequential actions for next-action reasoning and prediction
-- **source_data**: Raw unprocessed sensor data
+**Path naming convention:**
+
+| Level | Meaning | Example |
+|-------|---------|---------|
+| `{action}` | Action category with numeric prefix | `10_Stir_drinks` |
+| `{user}` | Participant ID | `user1` |
+| `{session}` | Scene–Environment–Trial index | `2-1-1` (Scene 2, Indoor, Trial 1) |
+
+- **HAR**: Singular well-defined actions organized by action category, for traditional classification tasks
+- **HAU**: Sequential action clips organized by user/session, for temporal and contextual understanding
+- **HARn**: Sequential action clips organized by action/user/session, for next-action reasoning
+- **source_data**: Original raw frames with full timestamps, before any task-level processing
 
 ## IMU Sensor Layout