Interconversion of captions described by ARIB-TTML and IMSC

Abstract

ARIB-TTML is a subtitle and caption standard for broadcasting systems in Japan. TTML profiles for Internet media subtitles and captions (IMSC) is a W3C recommendation. ARIB-TTML and IMSC are widely used in UHD satellite broadcasting in Japan and OTT operators; however, they have incompatible features and different description methods. These differences impede program exchange between broadband and broadcast. In this study, we propose a method for the interconversion of subtitles and captions described in ARIB-TTML and IMSC. We organized the features of each standard and proposed a conversion algorithm. The interconverted caption files were confirmed using a JavaScript-based caption renderer.