Note the short camera streams in 12 takes

README.md

@@ -95,6 +95,11 @@ published `CameraCalibration` describes the 640x360 colour frame, so
 projecting a depth frame to 3D means halving `fx`, `fy`, `cx` and `cy`
 first.
 
+In 12 of the 179 takes the source mp4s carry a trailing empty packet and
+hold 80 real frames rather than 81, so all three camera streams are one
+frame shorter than depth and telemetry. `num_frames` follows the
+robot-state clock and reports 81.
+
 Eight of the 28 tasks have no successful rollout anywhere in the source, so
 those contribute failures only.