OK, you have a 5.1 receiver with a BD drive built in, correct? OK, then the audio from the BD player is never reaching the TV, it is being processed internally and sent to the speakers. I doubt there's anything in your player settings to send the audio to the TV, so we can discard that option. Anything played through the BD player/receiver (and I assume that Serviio is available here) is decoded as necessary and only the video is sent to the TV via HDMI. I was confused, thinking there was only a TV and BD player in the setup.
Now, unless both your TV and receiver box support something called Audio Return Channel (ARC), then you need the optical cable from the TV back to the receiver for the audio from anything originating from the TV. This includes over the air TV, as well as any Smart Apps (such as Netflix or connecting to Serviio). If both of your devices support ARC (My Samsung HU8550 does, and so does my Yamaha AV Receiver), then the optical cable is unnecessary. Be aware that only one of the HDMI jacks on the TV will support ARC, so that's the jack that must be used to connect back to the AV receiver. ARC does not support HD Audio (Dolby TrueHD or DTS Master Audio), so any TV app that would play HD movies from your Serviio box may not give you sound.
Unless your TV and receiver are the same brand and model, they likely support different video and audio formats. The profile in Serviio would differ for each device, and you need to make sure the correct profile is assigned to the device.
Not sure which TV you have, as Samsung series are letters, not numbers. There should be a letter (or 2) before the 7000 number. Also, what is the brand of BD player/receiver?
Dan
LG NANO85 4K TV, Samsung JU7100 4K TV, Sony BDP-S3500, Sharp 4K Roku TV, Insignia Roku TV, Roku Ultra, Premiere and Stick, Nvidia Shield, Yamaha RX-V583 AVR.
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