demux_New is called twice in InputSourceInit

[busybeeCS]

the function demux_New is called twice in InputSourceInit ,can anybody explain me why?
why does it return NULL when called the first time?

[diman23]

no guaranty but I think that:
vlc first tries to open an access_demuxer if it fails, than it opens an acces module first, and then it opens a demuxer (this is the second time demux_New is called)

[busybeeCS]

no guaranty but i think that:
vlc first tries to open an access_demuxer if it fails, than it opens an acces module first, and then it opens a demuxer (this is the second time demux_New is called)

then what is the access_demuxer ?
what is the difference between access_demuxer and access or demux?

[diman23]

access_demux module is an acces AND a demux 2 in 1
https://wiki.videolan.org/Hacker_Guide/Access_Demux/

e.g. in access_demux you can open a file on your own demultiplex it and send information to a decoder.
in a simple demux module you need to read from elementary stream (stream_Read) and in an access only you have to put this information to ELstream