This page documents user agent support notes for SMIL Techniques.
There is no universal standard format for representing captions in SMIL 1.0. Different user agents support different caption formats. A file in a supported format must be provided as the textstream src argument for the caption textstream.
QuickTime supports QTText caption files. Real-based players, such as RealPlayer and GRiNS, support RealText caption files. WindowsMedia supports SAMI files, but does not support SMIL. Flash does not support a specific file type, but can parse XML-based caption file; actually the FLVPlayback component support for SMIL is intended to detect parameters like movie/server url or multi-bandwidth indications specified in a <switch> tag.
Only RealPlayer supports SMIL 2.0.