Hello i use first time the Magic Lantern 2.3 in my canon 5d mark2,i want to capture video hdr put the video rec capture is flashing why? look here Magic Lantern 2.3 HDR with 550D - YouTube

Because it alternates different ISO settings every other frame.

Have a look at this.

A Simple Way To Shoot HDR Video Footage Using Magic Lantern (http://ae.tutsplus.com/tutorials/production/a-simple-way-to-shoot-hdr-video-footage-using-magic-lantern/)

Using this HDR feature on 5DM2 isn't a good idea, you basically half your FPS. On 7D or 60D probably better if you shoot at 50/60FPS. =)