Apple is planning a September 1 event at which the company is expected to unveil an updated iPod line-up.

In its usual cryptic style, Apple sent out email invitations revealing little more than the place and time of the event, which will be held in the Yerba Buena Center for the Arts in downtown San Francisco.

"It is time for the iPod Touch update," said analyst Rob Enderle of Enderle Group in Silicon Valley. "They tend to refresh the iPod now. The only thing that is heavy speculation is if they will mention Apple TV."

Apple traditionally rolls out improvements to its iPod line in September to position the trend-setting portable media players for the year-end holiday shopping season.

The event invitation features a large picture of an acoustic guitar, seen as another clue that the theme will be iPod and Apple's online shop iTunes.

The iPod Touch was expected to be upgraded to get "pretty much everything" the latest generation of the iPhone has except the radio signal, according to Enderle.

Features that the iPod Touch is expected to inherit from the iPhone 4 include video chat and a crisper resolution screen.

Analysts will be watching to see whether Apple responds to a move by Internet giant Google to expand its kingdom to the living room with an ambitious new service that lets people mesh television viewing with surfing.

"Google TV," developed in partnership with technology titans Sony, Intel and Logitech, fuses the freedom of the Internet with television programming.

Google executives vowed their TV platform will succeed where offerings such as Apple TV have foundered.

Google TV, which is powered by Google's Android software and Chrome Web browser, can be accessed using upcoming Web-enabled televisions from Sony or set-top boxes from Logitech that route Web content to existing TV sets.

Sony and Logitech said the sets and boxes will be available in the United States in time for the year-end holiday shopping season and be rolled out internationally next year.

Apple in 2007 released the first version of its digital media receiver that routes video, film, or television shows from computers to high-definition televisions but the company still refers to the devices as "a hobby."