The FASC baseline strengthens ASC by removing word types that are less likely to appear in groundtruth captions, e.g., "ah", "he", "hello," or "wish".
we only keep words with high P (w | GT ) P (w | ASR) values, i.e., words that would be indicative of the groundtruth class if we were to build a Naive-Bayes classifier with addone smoothing; probabilities are computed only over the training set to reduce the risk of overfitting.