[qi:002] Google’s (GOOG) long-rumored, game-focused advertising initiative is going to come to life later this month, according to sources familiar with the Mountain View, Calif-based company’s plans. Google, which bought in-gaming advertising company, AdScape, earlier this year for about $23 million, will unveil its game-focused strategy in two steps, these sources tell me.

First, Google will launch a beta test with Redwood City, Calif.-based casual gaming startup Bunchball Games. As part of this test, Google is going to embed 15-second, “video-type” pre-roll and mid-roll ads in some of Bunchball’s casual games. Bunchball in recent months has started offering casual games as Facebook apps. Google is likely to announce this sometime next week, I’m told. Both Bunchball and Google declined to comment.

The second step in Google’s game-focused advertising strategy will take place in December, when the company will, I’m told, will offer an ad-supported version of the PC game Psychonauts. This will be a downloadable game and will have 30-second pre- and mid-roll video ads, according to my sources.

Our esteemed gaming duo, Jane Pinkcard and Wagner James Au, have been tracking Google and its game-related advertising plans for a while now.

As Wagner notes, Psychonauts is not a casual game but an award-winning, story-heavy, cult hit. This “gamer’s game” from veteran adventure game designer Tim Schaefer and co-written by Erik “Old Man Murray” Wolpaw is now “out of print;” and can only be downloaded via Valve’s Steam network it can be accessed via such download sites as GameTap and Valve’s Steam network. As he put it: “Google launching with Psychonauts as a trial platform is like a new cable network launching with a Coen Brothers movie.”

Google’s pending launch comes at a time when the interest in casual gaming and in-game advertising is on an upswing. Google’s initiatives should give many start-ups building game-related advertising networks a pause.