Please provide a link to the model of tv you have, this will allow us to see possible solutions. (Already I can think of an HDMI to HDMI+Audio Splitter, this will always work.)
If you are running everything through an XboxOne or have a similar 1 device input you can run audio from that into the soundbar instead of going through the TV.
If you're willing to mess around with opening up the TV and splicing cables, you could take advantage of the TV's audio controller by splicing the speaker feeds (This is the best solution from an end-user perspective).