■ SPDIF Has No Audio ■ Why SPDIF Output Only 2.1 Channels? - The audio format of your source media may be uncompressed (lossless). Uncompressed surround sound audio is not supported by digital (S/PDIF) connections due to bandwidth limitations. When your lossless 5.1 or 7.1 audio content is sent through the Digital S/PDIF connection, data will be lost which can result in limited 2-channel audio playback. Uncompressed surround sound is universally incompatible with digital (S/PDIF) audio.
Digital (S/PDIF) audio supports a. 2-channel PCM audio b. Compressed surround sound audio (Dolby Digital, DD+, DTS, DTS-ES)
Digital (S/PDIF) audio does NOT support a. More than 2-channels of PCM audio b. Uncompressed surround sound audio (DD-TrueHD, DTS-Master Audio)
Playback of digital surround sound is dependent on a variety of factors, including the audio format of your source media, your playback software, and your audio receiver. Digital (S/PDIF) channel settings are managed by the source and playback devices, and cannot be manually configured like analog audio.