Fix act action queue (#185)

lerobot/common/policies/act/modeling_act.py

@@ -98,13 +98,13 @@ class ACTPolicy(nn.Module, PyTorchModelHubMixin):
         batch["observation.images"] = torch.stack([batch[k] for k in self.expected_image_keys], dim=-4)
 
         if len(self._action_queue) == 0:
-            # `self.model.forward` returns a (batch_size, n_action_steps, action_dim) tensor, but the queue
-            # effectively has shape (n_action_steps, batch_size, *), hence the transpose.
-            actions = self.model(batch)[0][: self.config.n_action_steps]
+            actions = self.model(batch)[0][:, : self.config.n_action_steps]
 
             # TODO(rcadene): make _forward return output dictionary?
             actions = self.unnormalize_outputs({"action": actions})["action"]
 
+            # `self.model.forward` returns a (batch_size, n_action_steps, action_dim) tensor, but the queue
+            # effectively has shape (n_action_steps, batch_size, *), hence the transpose.
             self._action_queue.extend(actions.transpose(0, 1))
         return self._action_queue.popleft()