README: add a Previews section (stereo preview videos)

README.md

@@ -120,6 +120,19 @@ gripper = root["data/robot0_gripper_width"][s:e]       # (T, 1)
 store.close()
 ```
 
+## Previews
+
+One training episode per task as a short video with its stereo sound (headphones recommended).
+
+| Path in this repository | Task | Episode | Target side | Length | Size |
+|---|---|---|---|---|---|
+| `previews/c4_T1_ep41_preview.mp4` | T1 Ring-off | 41 | left | 14.5 s | 0.40 MB |
+| `previews/c4_T2_ep50_preview.mp4` | T2 Covered phone | 50 | left | 22.9 s | 0.77 MB |
+| `previews/c4_T3_ep24_preview.mp4` | T3 Call bell | 24 | right | 26.3 s | 0.83 MB |
+| `previews/c4_T4_ep21_preview.mp4` | T4 Animal feeding | 21 | left (dog) | 26.0 s | 0.82 MB |
+
+Each video plays at 1x speed: wrist camera (left half) and external camera (right half) at 10 fps over the L/R 1–12 kHz level of the episode, H.264 448×288, with stereo AAC audio (48 kHz, 128 kbps); the left channel is `mic_0` and the right is `mic_1`, the 50 ms per-step windows joined in order (they do not overlap) and scaled by one gain for both channels, so the level difference between the channels is kept and nothing clips.
+
 ## Distractor sounds
 
 In our experiments, distractor sounds from ESC-50 are mixed into the audio as augmentation during training. ESC-50 is not included in this repository. Get it from the original source: https://github.com/karolpiczak/ESC-50