Those hooking up the latest MacBook Pros to an HDTV using an HDMI adapter can now do so a little more easily: Apple has updated its implementation of Mini DisplayPort to pass audio signals through to any device that supports them. Until now, the miniDP port only transmitted video, even though the DisplayPort spec supports optional alternate signal channels such as audio or USB.

Apple confirmed to Ars that the just-updated MacBook Pros will pass both video and audio signals to an HDTV or receiver when using an miniDP to HDMI adapter. Apple sells one such adapter from Griffin online, though alternative from suppliers such as Monoprice are also available. Apple doesn't have any plans at this time to make its own adapter, contrary to earlier speculation.

As for the current 24" LED Cinema Display, it still relies on USB for audio signals even when paired with the new MacBook Pros. Aside from the fact that this Cinema Display was designed before Apple updated its implementation of miniDP, the USB connection also takes care of the on-board iSight video as well as the built-in USB hub.

The change in the miniDP ports will make connecting a MacBook Pro to an HDTV a little easier. We have no doubt that Mac mini owners in particular will look forward to the new miniDP ports being added to a future hardware update, as that machine practically begs to be put to use as an HTPC.

UPDATE: Our friends at Italian Mac blog setteB.IT pointed up to this recent Apple knowledge base article noting that some HDMI adapters won't work with the new MacBook Pros if they aren't compliant with the 1.1a version or later of the DisplayPort spec. There are some adapters out there that aren't fully compatible, so be sure to check if you plan to buy one.

The unusual thing we noticed is that this warning also applies to owners of the most recent iMac revision. Those machines must then also have Apple's updated miniDP ports. To our knowledge, this is the first evidence that the new MacBook Pros weren't the first to enable audio passthrough via miniDP.