As far as we know, an MKV is just a container format, holding video, audio, image or subtitle files in it. The video and audio files in different MKV files can be encoded with different codecs. For example, an MKV file with DTS audio can't be rendered on Samsung Smart TV. That's why your Samsung TV refuse to play some thest MKV files with an unhelpful audio codec error message displaying right on your screen. To solve Samsung TV MKV playback issues, the best bet is to
convert MKV to Samsung Smart TV more compatible video format.