The team at Magic Lantern are always adding new and unexpected features to your favorite Canon video DSLR cameras and this time is no exception. HDR, or High Dynamic Range, video is achieved through the use of multiple ISO settings.
You will get two streams at half frame rate. For example, if you record 25p, you will get two 12.5fps streams. Interpolate them to 25fps and use your favorite HDR software to blend the frames.