Netflix took two big steps in the area of high definition this week, officially moving to HD streaming and tying up loose ends with HD DVD.

Going live on Wednesday via an upgrade to the Xbox 360, Netflix entered the arena of HD streaming with nearly 300 titles including “Heroes,” “La Vie en Rose” and “Flawless.” The service allows for streaming of nearly 12,000 standard-definition titles.

The New Xbox Experience, which debuted nationally on Wednesday, is a graphical user interface for the Xbox 360 that allows for Netflix streaming along with avatars for online games as well as the option to install games to the system to decrease load times and hardware noises.

Netflix members must be Xbox Live Gold members in order to enjoy streaming benefits without an additional charge, the company said.

“This is an important and exciting moment for Netflix and Xbox,” Netflix Chief Marketing Officer Leslie Kilgore said.

“We believe the New Xbox Experience, with thousands of choices available to be streamed instantly from Netflix as one of its key enhancements, offers consumers a great at-home entertainment option and provides terrific value as a holiday gift idea,” she said.

The HD streaming element of Netflix on the Xbox 360 will feature only standard-definition audio. The company said it is looking to add titles and multichannel audio “eventually.”

The company also sent e-mails to users with HD DVD titles in their rental queues last week, stating that effective Dec. 15, the rental service will no longer provide HD DVDs, technology blog Engadget reported.

Netflix has been slowly phasing out HD DVD support since it went solely Blu-ray in February.

Users who have HD DVD titles in their queues will have standard-definition versions of the titles swapped in on Dec. 15.