Support for audio output over the Mini DisplayPort connector debuted with the latest generation of MacBook Pros. Apple now sells a revised VESA-compliant adapter for HDMI output that extracts both audio and video signals from the Mini DisplayPort connector.
A support document for the new model indicates the 2010 MacBook's Mini DisplayPort connector can be used to "connect to an external display, projection device, or TV that uses a DVI, HDMI (audio and video) or VGA connector with a separate adapter. You can purchase adapters for supported video formats from Apple."
Third parties are also able to sell Mini DisplayPort to HDMI adapters (or complete cables) that deliver both audio and video signals, although some existing Mini DisplayPort to HDMI cables do not yet support audio, so buyers need to be aware of the signals supported by a given cable or adapter.
Previous Mac models with Mini DisplayPort required a separate cable to deliver audio output to a TV in addition to using HDMI to deliver video, either using the optical or analog minijack output or alternatively a USB port delivering digital audio output using a more expensive USB+Mini DisplayPort hybrid adapter.