Fix for visual observations (#847)

python/unitytrainers/ppo/trainer.py

         feed_dict = {self.model.batch_size: 1, self.model.sequence_length: 1}
         if self.use_visual_obs:
             for i in range(len(brain_info.visual_observations)):
-                feed_dict[self.model.visual_in[i]] = brain_info.visual_observations[i][idx]
+                feed_dict[self.model.visual_in[i]] = [brain_info.visual_observations[i][idx]]
         if self.use_vector_obs:
             feed_dict[self.model.vector_in] = [brain_info.vector_observations[idx]]
         if self.use_recurrent:
                 if self.use_visual_obs:
                     for i, _ in enumerate(self.model.visual_in):
                         _obs = np.array(buffer['visual_obs%d' % i][start:end])
-                        (_batch, _seq, _w, _h, _c) = _obs.shape
-                        feed_dict[self.model.visual_in[i]] = _obs.reshape([-1, _w, _h, _c])
+                        if self.sequence_length > 1 and self.use_recurrent:
+                            (_batch, _seq, _w, _h, _c) = _obs.shape
+                            feed_dict[self.model.visual_in[i]] = _obs.reshape([-1, _w, _h, _c])
+                        else:
+                            feed_dict[self.model.visual_in[i]] = _obs
-                            (_batch, _seq, _w, _h, _c) = _obs.shape
-                            feed_dict[self.model.next_visual_in[i]] = _obs.reshape([-1, _w, _h, _c])
+                            if self.sequence_length > 1 and self.use_recurrent:
+                                (_batch, _seq, _w, _h, _c) = _obs.shape
+                                feed_dict[self.model.next_visual_in[i]] = _obs.reshape([-1, _w, _h, _c])
+                            else:
+                                feed_dict[self.model.next_visual_in[i]] = _obs
                 if self.use_recurrent:
                     mem_in = np.array(buffer['memory'][start:end])[:, 0, :]
                     feed_dict[self.model.memory_in] = mem_in