Update README.md

Add action context

README.md

@@ -19,15 +19,40 @@ Current version: v1.1
 Contents of train/val_v1.1:
 - **video.bin** - 16x16 image patches at 30hz, each patch is vector-quantized into 2^18 possible integer values. These can be decoded into 256x256 RGB images using the provided `magvig2.ckpt` weights.
 - **segment_ids.bin** - for each frame `segment_ids[i]` uniquely points to the segment index that frame `i` came from. You may want to use this to separate non-contiguous frames from different videos (transitions).
-- **actions/** - a folder of action arrays stored in `np.float32` format. For frame `i`, the corresponding action is given by `driving_command[i]`, `joint_pos[i]`, `l_hand_closure[i]`, and so on. The shapes of the arrays are as follows (N is the number of frames):
+- **actions/** - a folder of action arrays stored in `np.float32` format. For frame `i`, the corresponding action is given by `joint_pos[i]`, `driving_command[i]`, `neck_desired[i]`, and so on. The shapes and definitions of the arrays are as follows (N is the number of frames):
+  - **joint_pos** `(N, 21)`: Joint positions. See `Index-to-Joint Mapping` below.  
+  - **driving_command** `(N, 2)`: Linear and angular velocities.
+  - **neck_desired** `(N, 1)`: Desired neck pitch.
+  - **l_hand_closure** `(N, 1)`: Left hand closure state (0 = open, 1 = closed).
+  - **r_hand_closure** `(N, 1)`: Right hand closure state (0 = open, 1 = closed).
+  #### Index-to-Joint Mapping
   ```
-  {
-    joint_pos: (N, 21)
-    driving_command: (N, 2), 
-    neck_desired: (N, 1), 
-    l_hand_closure: (N, 1), 
-    r_hand_closure: (N, 1),
-  }
+   {
+        0: HIP_YAW
+        1: HIP_ROLL
+        2: HIP_PITCH
+        3: KNEE_PITCH
+        4: ANKLE_ROLL
+        5: ANKLE_PITCH
+        6: LEFT_SHOULDER_PITCH
+        7: LEFT_SHOULDER_ROLL
+        8: LEFT_SHOULDER_YAW
+        9: LEFT_ELBOW_PITCH
+        10: LEFT_ELBOW_YAW
+        11: LEFT_WRIST_PITCH
+        12: LEFT_WRIST_ROLL
+        13: RIGHT_SHOULDER_PITCH
+        14: RIGHT_SHOULDER_ROLL
+        15: RIGHT_SHOULDER_YAW
+        16: RIGHT_ELBOW_PITCH
+        17: RIGHT_ELBOW_YAW
+        18: RIGHT_WRIST_PITCH
+        19: RIGHT_WRIST_ROLL
+        20: NECK_PITCH
+        21: LEFT_WHEEL
+        22: RIGHT_WHEEL
+    }
+  
   ```