video_sampling.longest_edge -> 512

Otherwise I think frames will be extracted at 384 and then upsampled to 512 for processing.

preprocessor_config.json

@@ -29,7 +29,7 @@
     "fps": 1,
     "max_frames": 64,
     "video_size": {
-      "longest_edge": 384
+      "longest_edge": 512
     }
   }
 }