In this paper, we introduce a subtitle synchronization and positioning system designed to increase the accessibility of deaf and hearing impaired people to multimedia documents. The main contributions of the paper concern: a novel synchronization algorithm able to robustly align, without any human intervention, the closed caption with the audio transcript and a timestamp refinement technique that adjusts the subtitle segments duration with respect to the audiovisual recommendations. Finally, we introduce a novel method that performs a high level understanding of the multimedia content, in order to determine the subtitle optimal positions, within the video frame, such that they do not overlap with other relevant textual information. The experimental evaluation performed on a large dataset of 30 videos taken from the French national television validates the approach with average accuracy scores superior to 90% regardless on the video genre. The subjective evaluation of the proposed subtitle synchronization and positioning system, performed with actual hearing impaired people, demonstrates the effectiveness of our approach.