I replaced my digital video recorder (DVR) which is located inside the roof. The old DVR has an existing Ethernet cable but not HDMI cable running from the roof to an Ethernet jack on the wall. I plugged the Ethernet cable of the old DVR to my new DVR and would like to run an HDMI cable through the wall and connect to the TV so that I can view the footage on the TV. I did tried to run a 15m-long HDMI cable through the same wall cavity as the Ethernet cable, but I couldn't find the other end of the HDMI cable even after I pushed the HDMI cable all the way down the cavity. Both the DVR and the roof cavity are located above the room where the TV is located.
Photos of the DVR, roof cavity and the hole left on the wall after the Ethernet jack was pulled out are attached.
I would like to ask: Do I need to use a fish tape? If so, how long should the fish tape be? Could the fish tape come out of the hole on the wall without me having to manually pull it out? Note that the photo showing the roof cavity has a braided HDMI cable plugged in.