EyeTV is a device that takes a television cable feed and puts it into the computer where it is viewed in a separate window. Then it works the same as your television i.e. you change channels depending what you want to watch. You can also record the television feed to your hard drive.
It's quite handy. I keep a news channel going in a small window at the bottom of the computer screen while I'm doing other stuff, and enlarge it if a story peaks my interest.
I just used the EyeTV feed as a source of moving images to test with Grab. Since you're still getting blank images, you're beyond my ability to provide any helpful input although logic suggests, if you're getting the same result no matter which tool you use, the problem isn't the tools.
That suggests to me that, even though you may use your camera to get the low-rez images, you still have a problem that needs a solution. Good luck with it.
ryck