Yes it is!

Different devices may have different signal strengths. Another dvd player may give you a different audio level. I have many devices and players set up to the same TV, and each one plays back at a significantly different audio level, which means we always need to adjust the TVs volume depending on what device we're playing the dvd/video on.

Each device has it's own volume setting, but it's a pain to try to get them all the same level so we never bother. It's just one of those things I think.