I got the elgato 4k X capture card, which passes threw surround sound (formats: linear PCM/uncompressed, dolby surround, dts, no dolby atmos and dtx X) but doesn't downmix it to stereo so your hearing the front 2 channels/speakers of 5.1 surround sound.
Everything your not hearing is coming from either the center channel/speaker or the 2 rear speakers/channels
plz downmix surround sound elgato, my live gamer 4k can downmix surround sound to stereo.