System for producing subtitles to internet audio-visual documents

In this paper, we present a system developed in our lab to provide subtitles to audio-visual shows and documents produced by Czech internet company Stream.cz. The main goal is to make these programs understandable also for deaf and hearing impaired persons. We describe the whole process that starts with extracting the audio channel from the document, then identifies speech and converts it to text (using either automatically generated or human edited transcripts), and eventually produces the subtitles synchronized with the audio and video tracks. We present the employed methods (including the adaptation of the system to the target data), compare results on various types of documents and provide some relevant statistics collected during the first year of practical deployment.