MPEG/TS Editor

I've got some MPEG Transport Streams recorded from Freeview. I'd usually use MPEG Streamclip to edit them but for some reason it's just displaying a white screen, the sound is working ok.

I can convert the streams with FFMpegX from TS->TS, then they work in Streamclip fine, but at 3GB each this takes ages and I only need a 1 minute clip from near the end.

Are there any alternatives to using Streamclip to directly clip some content from a TS file?