The battle has been going on for a few years about YouTube knowing copy infringement was happening and not doing anything to stop it. Google's response is that is up to content owners to notify the site about unauthorised vids.
The documents show that Viacom execs were actually interested in buying YouTube less than a year before they sued the video site. Google later bought the video site for $1.65 billion.
Google also claimed that Viacom had actually uploaded hundreds of videos to YouTube, offering as an explanation that the media giant knew that this kind of marketing worked.
In an opposing Viacom document, it claims that the Google video team told execs that YouTube was a good source of free content and highly sought after pirate clips.
The issue is whether Google did comply with Viacom’s copyright claims, because it would protect them under federal law as long as it promptly removed infringing material on request.
But Viacom are looking for more than $1 billion in damages, with claims that YouTube content owners knew that popular content like South Park was unauthorised.
Yet other media companies which were initially angered about YouTube have arranged revenue-sharing deals, while tech has been created which can now automatically detect copyrighted content.