GF_GenericSubtitleSampleDescriptor 2003 include/gpac/isomedia.h         u32 descriptionIndex, GF_GenericSubtitleSampleDescriptor *desc);
GF_GenericSubtitleSampleDescriptor  789 src/isomedia/sample_descs.c         u32 descriptionIndex, GF_GenericSubtitleSampleDescriptor *desc)