GstFileSrc Read data from a file FileSrc is used to read buffers from a file. It efficiently uses mmap and subbuffers. @element: @srcpad: @pagesize: @filename: @uri: @fd: @filelen: @curoffset: @block_size: @touch: @using_mmap: @is_regular: @mapbuf: @mapsize: @need_discont: @need_flush: @GST_FILESRC_OPEN: @GST_FILESRC_FLAG_LAST: