According to the specs released by Microsoft, the Xbox One only supports ultra high resolution 4K video. However, that capability may extend to gaming at some point in the future.
In an interview with Forbes, corporate vice president of marketing and strategy Yusuf Mehdi clarified the point about 4K gaming on the Xbox One. “There’s no hardware restriction there at all,” says Mehdi. So, the question isn't necessarily whether the console can support 4K gaming, but whether developers will make games at that resolution.
On the other hand, the Xbox One doesn't support standard-definition in either gaming or video. According to the information released by Microsoft, the only device only has an HDMI output, which means that it won't connect to older televisions featuring only composite or component inputs. Technically, you could buy converters that make the connection possible, but if you're considering that, your money would probably be better spent on an HDTV.
[Source: Forbes]