Screenshot - No Image - v4l2

Hello, i'm new with the raspi and i'm a bit confused. I have a LogiLink AV Grabber with the Hardware ID 534d:0021. There is no detailed name for it with lsusb. There are some threads here wich say, that this device is not supported by the OS because of bad or missing drivers. When i run hyperion-v4l2 --screenshot it returns a black image. when i use hypericon (windows) and try to load the screenshot it says "inappropriate ioctl for device" (ssh error). This is also the same error when hyperion tried to start normally. So every normal guy would think the device is not supported. But when i use the v4l2 test tool there is a top image of my av signal. Do anyone of you has a declaration for this.