HDMI audio output on ATI Radeon HD 4870

Discussion in 'Mac Pro' started by raymondthimmes, Oct 16, 2010.

  1. raymondthimmes macrumors member

    Sep 15, 2008
    Columbus, Ohio
    Hey fellow mac users,

    So I have a ATI Radeon HD 4870 on my Mac Pro and a 26" HDTV and I want to use it as my second display and utilize it's speakers (to watch movies while I work). Can I send audio through a mini display port to HDMI connector from this card or will i have to buy a secondary cable to plug into the audio out jack? Also are there syncing concerns with the two connections (hdmi and auto cable)

  2. diazj3 macrumors 6502a

    Jan 19, 2008
    The 4870 does not support audio over MDP/HDMI, so you'll have to stream the sound separately via the line out, headphone or optical built-in ports, or use a 3rd party alternative, such as a USB or Firewire interface.

    About a/v syncing or lagging issues, there shouldn't be any... unless the cables are longer than 10-15 meters or so, IME.

    There's also this or this USB/Optical/MDP to HDMI adapters, that take the video signal from the MDP, the audio signal from USB or optical as an audio interface, combines them, and streams them via HDMI. I haven't tried them, but they sound like a good idea.

    Nevertheless, if you plan to use the HDMI as a permanent option, IMO a better solution would be to replace the 4870 with the 5770 or 5870, once someone confirms the audio over MDP works also with earlier MPs.... I hope someone tries this soon and let us know.

  3. goMac macrumors 604

    Apr 15, 2004
    Has been tried, and it does. :)
  4. diazj3 macrumors 6502a

    Jan 19, 2008
    Are you sure? a 5770 or 5870 card in an older MP (2009 or earlier) does stream audio via the MDP->HDMI, totally confirmed? If so, that's great news! I've been looking for confirmation everywhere. Can you post the source(s) for this please?

  5. goMac macrumors 604

    Apr 15, 2004
    Yep, someone just posted in the "Apple Radeon 5770/5870 in pre-2010 Mac Pro's: What We Know So Far" thread reporting a success, actually.
  6. diazj3 macrumors 6502a

    Jan 19, 2008
    Not really: it hasn't been confirmed there yet. I've been following the thread, and so far only a couple have tested it with Apple 24" and 27" displays with the MDP input... but the Apple displays get the audio from their USB connections, and not from the MDP. Someone else saw the audio property on the system profile information, but did not actually checked it streamed audio, either via MDP or HDMI.

    Thanks anyway,

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