In a regulatory filing, Viacom said it was ordered to pay $383 million to settle the dispute, but that it intended to take the case to court due to "improperly excluded" evidence, the Los Angeles Times reported Wednesday.
Viacom purchased Harmonix in 2006 and, under terms of the purchase, paid a $150 million bonus based on 2007 sales or Rock Band.
However, that was the last bonus payment made. After 2007, Viacom not only failed to pay any additional bonus based on the game and its sequels, but asked for a refund on prior payments.
Rock Band and its sequels eventually sold 10 million units, but Viacom lost money on the deal and sold Harmonix to a private equity firm in 2010 for $50. In doing so, Viacom accepted a $50 million tax benefit, the Times reported.
Viacom said it had filed a suit in the Delaware Court of Chancery to challenge the arbitrator's decision.