There are more than 66 million people su®ering from hear- ing impairment and this disability brings them di±culty in video content understanding due to the loss of audio infor- mation. If the scripts are available, captioning technology can help them in a certain degree by synchronously illus- trating the scripts during the playing of videos. However, we show that the existing captioning techniques are far from satisfactory in assisting the hearing impaired audience to en- joy videos. In this paper, we introduce a scheme to enhance video accessibility using a Dynamic Captioning approach, which explores a rich set of technologies including face de- tection and recognition, visual saliency analysis, text-speech alignment, etc. Di®erent from the existing methods that are categorized as static captioning, dynamic captioning puts scripts at suitable positions to help hearing impaired audi- ence better recognize the speaking characters. In addition, it progressively highlights the scripts word-by-word via align- ing them with the speech signal and illustrates the variation of voice volume. In this way, the special audience can better track the scripts and perceive the moods that are conveyed by the variation of volume. We implemented the technol- ogy on 20 video clips and conducted an in-depth study with 60 real hearing impaired users. The results demonstrated the e®ectiveness and usefulness of the video accessibility en- hancement scheme.