Actually I just realised, it's not High Sierra's problem. It was since the Chromecast 2 updated its firmware to 1.28.100555 . Any input from Videostream team?!

Hello, used to be able to stream 5.1 audio mkv files using PCM options on my mac. Since upgrading to High Sierra, videostream kept getting stuck at initial buffering phase, unless changing audio to stereo. Anyone else has this problem?