A:Answer Both the HDMI ARC and the Optical Digital Audio port on the LG - 5.1.2-Channel Hi-Res Audio Sound Bar with Wireless Subwoofer and Dolby Atmos Technology, Model # SK9Y can pass multi-channel audio, like Dolby Digital. HDMI ARC is based on the IEC 60958-1 specification, which is basically S/PDIF that is also used as the foundation for optical audio. The flexibility of the HDMI standard (plus copy protection), however, allows additional audio formats to be transmitted over HDMI ARC than via optical but bandwidth is still very limited at 1Mb/s at the base level, although it can be pushed to pass more data. The limited bandwidth allows HDMI ARC to deliver stereo audio and compressed 5.1 surround. It can be pushed to transmit Dolby Atmos streams containing metadata but it requires an extension called Common mode that is not part of the base specification and must be actively supported in both TV (i.e. LG OLED) and receiver. However, bandwidth of standard HDMI ARC is too limited for compressed 7.1 surround and even more so for lossless audio (Dolby TrueHD or DTS-HD MA). Lip sync correction is also optional under ARC. If you are in need of any assistance, have additional questions, or would just like to see our helpful tips, check us out on Twitter @LGUSSupport Facebook https://www.facebook.com/LGUSA/ ^CP
