[Elizabeth McGraw-Austin] “Why isn’t FCP6 figuring this out for me?”
Because it can only do so much. It needs the clips to match a list of codecs, frame rates and frames sizes. If you have chosen a codec, rate or frames size that it has to render, then your clips are not in a format that FCp can automatically match your sequence settings to.
Thee are lots of variations in video land that FCP can work with. There are however, many more variations that it can’t edit natively. You need to choose a combination within the long list that FCP can edit without render.