CEO Tim Cook revealed during Apple's second-quarter earnings call that the company has sold 20 million units of Apple TV. That amounts to around $2 billion in revenue from the $99 streaming device. Last May, he revealed that the company had sold 13 million units.

Steve Jobs famously referred to the Apple TV as a hobby, and for the most part it hasn’t been a huge focus for the company -- despite its relative success in the market it competes in. Tim Cook has been slowly turning that ship around, calling Apple TV an “area of intense interest”, adding many new content sources and giving the device a more prominent spot on its website.

Cook revealed that in 2013 Apple generated more than $1 billion in sales from content directly purchased through Apple TV. "It didn't feel right referring to something that makes $1 billion as a hobby", he said.

He didn’t comment directly when asked about Amazon’s deal with HBO to bring older programming to its Fire TV and Prime customers, but said that the content available on the Apple TV is "extremely favorable" compared with Amazon's product. When asked about future plans, Apple's CEO didn’t reveal any upcoming Apple TV features or partnerships.

Apple TV started off as a hobby but has since become an important part of the company's product line-up. Cook is quite confident that the product is now a strong competitor to similar offerings from the likes of Amazon and Roku. "I'm feeling pretty quite good about that business and where it can go," he said.