2016 Obama's America Question

I just watched the documentary film 2016 Obama's America and there was one thing about the documentary which perplexed me and I could not find the answer to on my own on the internet. A large portion of the documentary seemed to have a narrative from Obama's voice himself. Where did these clips of his voice come from? I am not questioning the documentary from a conspiracy point of view or anything I was just wondering where they obtained the commentary of Obama speaking from. Did they cut clips from a bunch news clips or something? I thought it was a great documentary and everything but I was just wondering where they got the commentary from because it really sounded like Obama's voice.