matroska-demux: support matroska demux svp
original matroska-demux can not supoort secure webm container. so add some functions to support extract information about secure content, and protection event.
(cherry picked from commit d66c01db)
Due to an influx of spam, we have had to impose restrictions on new accounts. Please see this wiki page for instructions on how to get full permissions. Sorry for the inconvenience.
original matroska-demux can not supoort secure webm container. so add some functions to support extract information about secure content, and protection event.
(cherry picked from commit d66c01db)