VLC player clearly supports recording video on fly, but there seems to be no such support in libVLC.
I checked libvlc_media_player.h, and found no clue. For this functionality, I noticed that there were two patches submitted by Mark Lee in 2012, one of them is:
https://patches.videolan.org/patch/606/
Did I miss something? Is this already in libVLC?
If not, I am willing to help improve it. Please give me some guidance.