Does DisplayPort carry sound as HDMI does? Specifically, I am looking at Lenovo Laptops T410 or T510.
I'm wondering if the spec permits for audio over DP, and if possible whether the Lenovo laptops I mentioned implement it.
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Yes, the DisplayPort spec is an audio/video interconnect spec. It can carry both audio and video over a single connection.
It is rare a laptop implements audio-out over a digital video interconnect. My MacBook Pros don't do it over their DisplayPort outputs. More recent MacBook models reportedly may support audio-over-DisplayPort.
I also have Lenovo Thinkpad T410. Once you have a video playing, go to Control Panel, Sounds, Manage Audio Devices.
When you're in Manage Audio Devices, you'll see a list of devices and your TV speakers should be one of the options. Just choose it and set it as your default audio device and the sound should automatically come on the TV.
Q. Does DisplayPort also support audio?
A. Yes, DisplayPort supports multi-channel audio and many advanced audio features. DisplayPort to HDMI adapters also include the ability to support HDMI audio.
I wound up on this page however because my DisplayPort audio wasn't working. After searching many sites, I learned that the video driver (vs. audio driver) is responsible for the DisplayPort audio; while updating my video drivers (Intel HD Graphics 4600) I specifically noticed in the log it installed an Intel audio driver as well. After this driver update I'm able to see the TV/audio device listed under Control Panel->Sound (LG TV/Intel Display Audio), as well as under Device Manager as Intel Display Audio (in addition to my regular audio device).
As others have mentioned, it's up to the manufacturer to support/implement audio over DisplayPort. Other research has indicated that the DisplayPort to HDMI adapter must also support audio. Odds are if you're using a laptop with a common video device like Intel or AMD, they implemented audio over the DisplayPort and you just need the drivers for it.
Bottom Line: Update Video Drivers.
Clipped from Wikipedia (buyer beware, but this type of technical information tends to be truthier). It looks like it can be used as a passive pass-through to HDMI with an adapter.
Relationship with HDMI
The DisplayPort website states that DisplayPort is expected to complement HDMI. DisplayPort can emit HDMI video and audio using passive adapters connected to Dual-mode ports, and supports HDCP content protection used in the HDMI standard.
I can do audio out on my MacBook Air when using a Thunderbolt-to-HDMI adapter. Thunderbolt is a combination of DisplayPort and PCIe and is the same formfactor as MiniDisplayPort. When using a DisplayPort cable (MiniDisplayPort receptacle on one end, fullsize on the other, I can only do video, System Preferences > Sound does not give me the option to output sound to my TV/Monitor (this is the same monitor that I can output sound to when using a HDMI adapter, a Dell 3008WFP).
From my testing it may technically be possible to do audio over the DisplayPort protocol, ports and cables, but on a MacBook Air 13 inch, Mid 2011 model it is not possible with DisplayPort - it is possible with HDMI (presumably it is using PCIe-to-HDMI and not translating DisplayPort-to-HDMI).