Codecs can be finicky. What works for one may not work for another. Other applications can also install codecs that conflict. Usually, users have the most success with the Klite mega codec pack – here: https://codecguide.com/download_k-lite_codec_pack_mega.htm
Most Karaoke software, especially those that have been in development more than a decade, like Karaoki, are built on very similar CDG playback code/technology. It’s not all that conducive to supporting video playback natively (almost all of the deeply rooted karaoke software products on the market require codecs to play video for this reason).
If you plan to play a lot of video, you may want to check out LYRX as an alternative – which is built on our DEX 3 technology with our own native video decoder. No codecs are necessary. It’s here: http://www.lyrxkaraoke.com While it may lack some of the deeper functionality and customization that Karaoki provides, it now has the professional features users have requested since it was first launched over a year ago.