No Picture with Kmttg

I've installed the latest version of Kmttg on Windows 8.1. *.TIVO files downloaded from Tivo playback just fine, but I'm trying to decode them so I can work with them in video editing software. The *.mpg files coming out of Kmttg have audio but no picture.

I know this is probably a codec issue, but I'm reluctant to install random codec packages from the internet and expose myself to adware and other malware.

If this is a codec issue can someone point me to the right package from a reputable source?

Thanks.