Apple has filed another complaint against rival smartphone manufacturer HTC, alleging the Taiwanese-based company violated four of its patents related to software and technologies used in smartphones and other mobile devices.

The complaint was filed in a Delware district court. Both of the new patents - 6,282,646 and 7,380,116 - have the same description, referring to a "System for real-time adaptation to changes in display configuration". Both seem to deal with what happens when you plug in an additional video input or output into a device.

This is the second time that Apple has filed a lawsuit against HTC. In March, Apple sued HTC for violating 10 patents in a lawsuit with a federal court in Delaware. It also filed a suit involving 10 patents with the US International Trade Commission. The complaints were related to Apple's touchscreen control, hardware and software, and sought to ban the sale of phones such as the Nexus One, sold directly by Google, as well as phones using Microsoft's Windows Mobile Devices.

In May, HTC countersued Apple and filed a complaint with the ITC alleging that Apple violated five of its own patents. The complaint pertained to patents relating to power consumption in smartphones. HTC asked the trade court to ban Apple from selling the iPhone, iPad and iPod in the US.

In this latest complaint, Apple also reasserted claims on two patents included in the original case: "Unlocking a device by performing gestures on an unlock image" and "Conserving power by reducing voltage supplied to an instruction-processing portion of a processor."

Apple's first case against HTC is still pending. Apple is also engaged in a similar patent dispute with rival phone maker Nokia, though that case has been suspended pending the outcome of related ITC investigations.

Dan Moren at Macworld contributed to this article