Introduction : Canon EOS 650D
Although it has an 18 million pixel sensor, Canon's EOS 650D/Rebel T4i doesn't use the same CMOS device as other cameras in Canon's range. It uses a new Hybrid CMOS sensor that is designed to facilitate a combined phase detection and contrast detection autofocus system that operates during video recording and when Live View is activated.
Why DSLR Video is limit less than 30 minute per clip
The restriction that limits video recording in digitial cameras to 30 minutes could be abolished if the World Trade Organization's Information Technology Agreement (ITA) is expanded. Several countries, including the USA, have begun informal talks to extend the scope of the ITA to include products that are currently subject to tariffs and duty. At present, digital cameras' video cuts off after 30 minutes to avoid them being classified as video cameras (which attract 5.4% duty into markets including Europe). If the video cameras are added to the ITA, this distinction would no longer matter. (via Nikkei)