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Discussion Starter · #1 ·
I have audio over a DVI connection.
Yes, I know that's impossible, but it's true!

I've been developing HTPC project for about 9 months now, and I'm nearly done. I recently upgraded my mother board to a Biostar TA690G. While I was doing my Windows XP install, I had the following connections to my PC:
ethernet - to my router
VGA - to my secondary LCD monitor
Power - duh!
Cable TV coax - from the wall to my DVICO Fusion card
Mouse - USB
Keyboard - PS2
DVI - Using a RocketFish DVI-HDMI cable to my ViewSonic N3735W (my primary screen)

So imagine my surprise when Windows booted and I heard the familiar Windows Start noise over my 5.1 speakers!

I quickly double checked my connections, and sure enough, NOTHING ELSE was connected.

I fired up FusionHDTV and sure enough, crystal clear sound!

Next I looked at my Sound Blaster Extigy, which I use in stand-alone mode as a Dolby Digital Decoder.

The only thing hooked up to it was my ViewSonic N3735W via via optical/TOSlink S/PDIF.

I quickly realized the only way the PC was connected to the Extigy was by way of the TV. And to confirm my hypothesis, disconnecting the DVI cable or the TOSlink cut off the sound, as did turning off the TV.

I can only surmise that since the DVI and HDMI ports on my motherboard are both driven off the same bus, that the system must output the same audio-stream to both ports, and since I'm using the DVI-HDMI cable, the TV picks up the audio as it would from any other HDMI source.

I actually rather like this setup as I was already running audio from my PS3 the same way (HDMI-TV-TOSlink-Extigy). It saves the S/PDIF coax I used to run from my PC to the Extigy, so less cable clutter, plus now when I turn off the TV it automatically cuts audio from the PC, so I don't have to close/stop FusionHDTV or mute the volume when I'm done watching.

Incidentally, the latest Audio Drivers from the Biostar Website fix this "problem", as when I downloaded and installed them I lost audio. I've since rolled back the drivers so that I can keep my DVI-Audio setup.
 

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...Cable TV coax - from the wall to my DVICO Fusion card
I believe that's the input for your audio. The DVI is transmitting Video only.
 

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Discussion Starter · #3 ·
I believe that's the input for your audio. The DVI is transmitting Video only.
???

I don't think you quite understand. That's the cable signal FROM the cable company.

Sure it caries audio IN to the PC, along with video. That's what cable TV is.

The thing is that the audio is going OUT from the PC through the DVI port.



My speaker (Logitech X-540's) are ONLY hooked up to------

My Dolby Digital Decoder (Sound Blaster Extigy).
The Extigy is NOT being used as a sound card. It has NO CONNECTIONS (not USB, not audio) to my PC. My Extigy is ONLY hooked up to-------(TOSlink)-------

My TV/Monitor (ViewSonic N3735W). My TV is hooked up to my PS3 (HDMI), my Cable TV (coax Cable TV) AND it's hooked up to -------(DVI/HDMI)--------

My PC's DVI-D port. That's the onboard DVI-D port from the AMD690G Chipset's IGX Radeon x1250.
The ONLY other connections hooked up to my PC are: ethernet, VGA, mouse, keyboard, Cable TV and power.

And yet, I get my PC's audio (game, mp3's, whatever) on my Logitech speakers.

And as I mentioned before, if I:
a)Turn off the TV
b)Unplug the DVI/HDMI cable (PC-TV)
c)Unplug the TOSlink (TV-Dolby Decoder)
The audio stops...

Therfore, audio signal MUST be traveling through the DVI port, up the DVI-HDMI cable to my TV, and back down the TOSlink to my Dobly Decoder (Extigy).

If someone else can point out a flaw in my logic, I'd love to hear it!

AS I said
I KNOW DVI is video only. Hence my statement "Yes, I know that's impossible, but it's true!"[/B]
 

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Here's the thing -- disconnect just the DVI and see if the Ta-duh is still there. I'll bet a virtual quarter that it will be. Now reconnect the DVI and disconnect the TOSlink and try again; same bet.

Am I up a virtual 50 cents? If I am I'd like a virtual candybar.
 

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Discussion Starter · #5 ·
Here's the thing -- disconnect just the DVI and see if the Ta-duh is still there. I'll bet a virtual quarter that it will be. Now reconnect the DVI and disconnect the TOSlink and try again; same bet.

Am I up a virtual 50 cents? If I am I'd like a virtual candybar.
And as I mentioned before, if I:
a)Turn off the TV
b)Unplug the DVI/HDMI cable (PC-TV)
c)Unplug the TOSlink (TV-Dolby Decoder)
The audio stops...
I meant if I do any ONE of those things the audio stops.

I just tried it again. I unplug the DVI and I gert no Windows "ta-da", no MP3 playback, no sound of any kind.
Plug the DVI back in, and the sound comes back.
Turn off the TV, sound goes away, turn the TV back on, sound comes back.
Unplug the TOSlink, no sound. Plus the TOSlink back in, and I'm back to rockin'!

Looks like you owe me a virual half dollar...
 

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Discussion Starter · #7 ·
Nice....

Now I just gotta get a really big printer so I can make a life-sized cutout....
 

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Using a RocketFish DVI-HDMI cable to my ViewSonic N3735W
This is not a pure DVI-D connection. If it were, you'd have no sound. The DVI-I/or A connection must contain the sound capability from a PC and is connected to HDMI at the other end. The HDMI is carrying the sound as it should. If you had a pure DVI connection, you would have no sound.

This is the same for the cable that Bell supplies with it's 92XX PVR. It has HDMI at both ends and a DVI adaptor in the middle for people with DVI TVs. The particular DVI carries the audio on to the HDMI connector at the other end of the cable.

You both now owe me $1 for the explanation. ;)
 

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Discussion Starter · #10 ·
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It's actualy a DVI-D port wit NO analogue capabilities at all.
I realize it's not a "pure DVI" connection, and I understand that the cable is essentially an HDMI cable with a DVI-HDMI adapter built in at one one. So I can see how the cable is carrying the audio.

I'm more supprised that the motherboard's DVI-D port is able to output the sound at all.

The 690G's IGX subsystem (Radeon X1250) supports up to 4 outputs - 1 HDMI, 1 DVI-D, 1 VGA, 1 Video/S-Video/Component.
However there are only 2 graphic streams running those connections; 1 digital stream powereing the DVI-D and HDMI, and an analogue stream running the VGA and video ports.

Now obviously the digital sream integrates an audio signal from the onboard Realtek sound system to allow for audio over the HDMI port.
My assumption is that due to a glitch in the system, the Realtek is also pushing audio through the DVI-D port - basically treating it like anoher HDMI port.

As I said, the latest driver from the Biostar website fixes the "problem"...
 

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Discussion Starter · #11 ·
I thought the ability to transport sound over DVI was a property of the ATI 690G chipset as well as all the new HD Radeons.
I don't know...

My previoius Asus 690G based mobo didn't output audio over the DVI-D, and the latest drivers from Realtek/Biostar cut off the audio over DVI-D on my current TA690G mobo.

I know the Radeon HD cards that have HDMI ports have onboard audio, so they might be able to do it... But I hadn't heard of audio over DVI...
 

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I'm guessing that if one purchases a DVI-HDMI cable, the DVI end seems to make use of a couple of the wires to send audio. I assume that those wires are unused for a "DVI only" connection.
 

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Discussion Starter · #13 ·
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That's along similar lines as I was thinking, except I don't think it was a planned feature (since it's disabled in the updated drivers).

Basically I figure that the 690G's digital video stream is setup as an HDMI stream, and then mobo companies basically use the internal eqivilant of an HDMI-DVI converter to create a DVI-D port. I guess a few of the unused lines in the DVI-D port end up with the audio.
With a standard DVI-D to LCD connection, the extra lines would be ignored. but with a DVI-HDMI cable, the extra lines are fed back to the HDMI cable, and away you go!
 

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Discussion Starter · #16 ·
Tikker is mostly right.
This motherboard is brand new, and previously I was using a Asus M2A-VM, which lacks an onbaord HDMI port, so I was forced to use an DVI-HDMI cable for video and s/pdif coax to my Dolby decoder.
I was planning on eventually switching to an HDMI cable, but for setup purposes it was easier to use the existing DVI-HDMI cable.
 

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Hi guys.

I've ordered a motherboard from ASRock (4CORE1333-FULLHD) just recently that has the Radeon x1250 built-in. I chose it for my HTPC project because among the list of features are:

  • Chipset embedded HDMI Audio which supports HDMI signal through DVI-D port by using DVI to HDMI adapter (not bundled)
  • Supports HDCP function with DVI-D port, to enjoy better quality with High Definition HDCP Encryption contents
  • Supports 1080p Blu-ray (BD) / HD-DVD playback with DVI-D port

Basically - as you have been speculating about - this is a feature of the x1250 / RS600 chip and is intentional. If you were not able to output audio through the DVI port of these boards, they wouldn't be as good for HTPC use because most amplifiers require that sound is transmitted together with the picture digitally via the HDMI cable.

If sound is not transmitted via HDMI, the HDCP Encryption is not supported and the ability to play Blu-Ray and HD-DVDs is lost.
 

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hi, i stumbled across this post whilst I was trying to understand why my DVI enabled TV (no HDMI) has managed to play sound from my ps3 without any auxiliary cables or any other modifications.

I have a HDMI > DVI adapter attached from PS3 to crappy store brand TV.

I realised it plays audio via the hdmi-dvi link when i attached the phono's from the Multi-AV lead to my amp, and sound was still coming from my TV.

I dont understand how the HDMI cable is sending sound to my TV via the DVI input - it makes no sense. I have an xbox 360 elite on the way, i wonder if this also works the same.

I have a video available for any non-believers, i just wondered if anyone has an answer.

cheers
buncey
 

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Nothing out of the ordinary, ATI's new HD 3800 series of video cards can pass audio via the DVI to HDMI port including in the packages. I'll be using one of these cards for my HTPC as soon as it arrives early next week.
 

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Yeah, the 2600xt does this as well. It's a DVI port on the card and they provide a DVI to HDMI adapter. The DVI port must have slightly different pins or something because the DVI to HDMI adapter I was using on my previous video card worked fine but wouldn't pass video when used with the ATI card. You had to use ATI's DVI to HDMI adapter.

It through me for a loop for a good hour or so.

Jimmy.
 
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