diff --git a/datasets/TTSDataset.py b/datasets/TTSDataset.py
index cbb4bf97..319c2598 100644
--- a/datasets/TTSDataset.py
+++ b/datasets/TTSDataset.py
@@ -176,6 +176,8 @@ class MyDataset(Dataset):
         if isinstance(batch[0], collections.Mapping):
 
             text_lenghts = np.array([len(d["text"]) for d in batch])
+
+            # sort items with text input length for RNN efficiency
             text_lenghts, ids_sorted_decreasing = torch.sort(
                 torch.LongTensor(text_lenghts), dim=0, descending=True)
 
@@ -187,6 +189,7 @@ class MyDataset(Dataset):
             speaker_name = [batch[idx]['speaker_name']
                             for idx in ids_sorted_decreasing]
 
+            # compute features
             mel = [self.ap.melspectrogram(w).astype('float32') for w in wav]
             linear = [self.ap.spectrogram(w).astype('float32') for w in wav]
 
@@ -211,7 +214,7 @@ class MyDataset(Dataset):
             assert mel.shape[2] == linear.shape[2]
             timesteps = mel.shape[2]
 
-            # B x T x D
+            # B x D x T --> B x T x D
             linear = linear.transpose(0, 2, 1)
             mel = mel.transpose(0, 2, 1)