I am having an issue getting my T4i to record RAW video. It gives me a few loading bars, then stops recording and those few seconds were not written on the card. I am using a 64Gb Sandisk (ultra) class 10 SD card, and a 16bit Transcend class 10 card. I'm aware it will not do full 1080 on this camera, but I haven't even been able to get it to record in 720. Please help.
You have to run
Debug -> Benchmarks -> Card R/W benchmark (5 min)
to find out what your cards are able to do. "Class 10" just says the card will do at least 10 MByte/s and that's enough for Canon's 1080p but will not at all do any good with RAW data floods (stream is not strong enough a word for this amount of data).
Make sure you disable "Auto power off" on your cam before running this test.
If your card miss 40 MByte/s (write) in photo mode by far ... well ... sorry.
Ciao
Walter