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Tv's do not have settings like that. They do however have limitations on what type incoming of video signal they can display. Depending on the model an hdmi port on a given tv will be able to accept a signal like 1920x1080, or 1280x720, or 720x480. These are the standard video resolutions of devices like bluray players, cable boxes, etc. Anything outside of those signal formats and the tv won't display anything.
So, if the mac has a way to change resolution output of the hdmi, that is where you need to start. There is no setting in the tv. It either will display the video format of the connected device or it wont. Depends on the specifications of the model tv you have.
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