All connects are made with HDMI
Connect the soundbar to the TV (use the ARC-HDMI input
Connect the cable box to the TV (use other HDMI input)
Connect the BD player to the sound bar HDMI input.
Turn on ARC in the the TV and maybe in the sound bar.
Select the HDMI input of the sound bar, and HDMI-ARC on the TV for BD
Select the ARC input of the soundbar and HDMI 2 on the TV for cable box