ATI hdmi where does it get the sound from?

First post here. Just a question left unanswered even after much googling and many threads.

My setup is ATI 4870 + a GigaByte motherboard capable of Dolbly-Digital Live that can send the encoded sound to the SPDIF out.

I'd like to use the HDMI-out of the 4870 to connect my pc to my HDTV.

The question is: since I read that - unlike some nvidia cards that feature an spdif-in internal connector - the 4870 has no such thing, then what sound does the ati 4870 send to its HDMI-out? Can it be that the encoded sound from my mobo passes through the ATI card and through the HDMI? Or if I use the HDMI-out for sound (ATI HDMI audio device) then I effectively disable anything that has to do with the sound coming from the motherboard? Finally, if i can route this mobo encoded sound from the 4870, then can I also use the DVI-HDMI dongle and route this sound from both the DVI and HDMI outputs that my 4870 features?

Thank you.
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  1. I guess the driver sets itself up as a sound card and the signal is sent through the PCI-E port.
  2. yes but what signal?

    The original source, or the 5.1 encoded one?

    How can I force the original source to *first* pass through the motherboard's sound device - and through any process by the drivers/software of this device, such as the DDLive encoding - and, "coming out" of the motherboard, to *then* pass through the ATI card and through the HDMI output?

    So, if i'm not expressed correctly, basically what i want is to use the software of my mobo's sound device to do stuff and create a DD stream and pass *that* stream through HDMI.

    Again, thanx for the answers.
  3. Edit: My motherboard is GigaByte P45-DS4 and has the Realtek ALC889A sound chipset onboard.
  4. The Radeons have a sound chip on board for use with the HDMI connector so none needed on the MB.

  5. thx for the answers so far.

    I agree that the mb is not needed, but can I use the encoding capabilities of the realtek drivers/software and then pass the encoded 5.1 signal through the ati card and hdmi?

    What i am basically asking is this:

    1.The mobo realtek states that it takes the original source, encodes it and then outputs the stream through the spdif.
    2.The ATI states that it takes "the sound", combines it with the video and outputs the combined stream through the hdmi.

    The question is: what "sound" does ATI get? how can i control this process and tell the pc that the sound must first pass to step 1 and then pass to step 2? maybe this is what the ATI HDMI driver does? it takes the spdif output of the mobo as an input to the graphics card? or does it function the other way round? the realtek/mobo must be told to send the spdif output somewhere and if someone (ati card) asks for the sound source, then this output is returned?

    or maybe am i completely wrong in any of these claims?

    Thanks for your answers, again.
  6. if your motherboard has an spdif out you can set it as the default playback device. that and send it to a receiver. if you have no receiver then this won't work, but it's a moot point anyways because you're probably running the sort of system that wouldn't get much good from the dolby stuff.
    my point is, unless you have a high end audio set up (like $8000) you won't be able to notice a difference between the dolby audio stream, and the re-encoded version that the ati card did.
  7. As far as I know there is no way to do a pass through on the ATI cards. They have their own Realtek chip that supports the following (coppied from ATI's site)
    Integrated HD audio controller with support for stereo and multi-channel (up to 7.1) audio formats, including AC-3, AAC, DTS, DTS-HD & Dolby True-HD4, enabling a plug-and-play audio solution over HDMI.
  8. The Onboard REALTEK audio with the motherboard and the ATI 4870 audio are two different sound chips. One has nothing to do with the other. One does not need the other to function(Vice Versa).

    The Onboard REALTEK sound chip drives the analog and spdif output of the motherboard. REALTEK can produce 5.1 or 7.1 analog audio. The SPDIF can only support stereo or 5.1 audio.

    The ATI-4870 sound chip drives the audion through the HDMI. This is capable of 7.1 audio stream to your TV or Receiver with HDMI interface.

    Selection of Audio can be selected on the AUDIO section of the CONTROL PANEL. The options will be ATIHDMI Output, SPEAKERS(REALTEK), SPDIF Out(REALTEK). For example if you select the ATI-HDMI thats where your sound will be. The audio will come out on the OPTION defined as default playback.
  9. so, to see if i get this right.. Nvidia cards with an internal spdif-in connector can do a pass-through but ATI cards with this sound chip can only pass the *original* sound (meaning that mixer/equalizer settings, encodings etc based on the MOBO sound device's software have not been applied to the sound) through the HDMI?
  10. Sorry about the double post, one more question.

    If the ATI card passes the original sound through the HDMI, can't it be fooled by something (drivers/software/whatever) to take a processed sound (eg encoded 5.1 stream) instead of the original one
  11. You basically have it right: NVIDIA cards simply use a SPDIF connector to transmit sound, with all the limitations that come with SPDIF (Stereo PCM or Dolby Digital/DTS streams).

    ATI cards do NOT use the chip on your mobo, they actually come equipped with its own Realtek chipset on the card itself. You get all the benifits of HDMI (Raw 7.1 PCM), but are limited to the quality of the chipset on the card.
  12. Thank you for clarifying this. No pass-through. So no mixer/encoding settings apply to this sound stream... I think i would have prefered nvidia solution...
  13. yep, my GTX 260 has the SPDIF header right next to the 6 pin power connector...

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