Understanding HDMI and its compatibility with onboard audio - AVS Forum
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post #1 of 4 Old 03-19-2013, 09:02 AM - Thread Starter
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Dear AVS-HDMI-Forum,

I was wondering if you could help me out to understand how the voice/sound-flow for HDMI works, as it seems that I´ve misunderstood some basic things. I´ll try to be concise with the issue I´m having.

The scenario:
I've got a HTPC hooked up via HDMI (vga msi 560ti) to a LG flat TV.
Works flawlessly, sound and video are perfect, couldn´t work better.
The motherboard used is a Gigabyte ga-gma880-ud2h.
I also connect to the front panel of my pc with a headset for gaming purposes and when I don´t want to disturb anyone at home with music or movie sound.

The problem:
I´m unable to use the microphone from my headset when connected to Front or Backpanel.
I can´t make a single Skype call, TeamSpeak or the inbuilt Steam Chat, the mic is not being recognized. I tried everything, believe me, searched on hundreds of sites, found people with similar problems, but I did not manage to solve this issue: I fiddled around with the Realtek High Definition Audio Controller, disabled front panel detection, enabled both front and rear panel, enabled mixer, played with the recording volume, enabled mic boost…still nothing – I can´t hear myself.
All I get to see is the status bar moving on the “Recording Tab”, but moving up and down in accordance with the sound played through the Headset.
I checked in the Gigabyte Forum, and I asked about this issue and I pointed out that I thought that HDMI is the culprit, but they told me not.

The understanding:
Ruling out the possibility that I have a HW-issue on the onboard audio, I´m inclined to think that I can´t use the mic when my htpc connected to the TV via HDMI.
To conclude, I would need some advice to understand how the architecture of HDMI works... :

1. With HDMI, does the PC know what to do with the audio it's sending back, as video cards tend to be output only ? I I believe that I would need to send the signal as well through the video card, it would need to have additional audio-in functionality like for example with a S/PDIF cable ?

2. My msi card does not have an additional audio in connector, but it does have 2 x Dual-Link Dvi. Would the mic work, if I connect the PC through the DVI output to the LG-TV with the good old RGB cable & then, connect the motherboard with a S/PDIF cable to the back of the LG ?

3. Is HDMI connection only for output, and no input ?

Don´t know if it makes sense to get an additional Sound Card for this purpose, a budget one.

If HDMI is blocking the possibility of recording, I would switch then just the cables whenever I need them for VOIP or gaming.

Thank you all for reading my and thanking in advance for any inputs.
Kind regards,
Ken

If you are not now, you never were.
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post #2 of 4 Old 03-19-2013, 09:22 AM
 
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Quote:
Originally Posted by K3npachi View Post

...
1. With HDMI, does the PC know what to do with the audio it's sending back, as video cards tend to be output only ? I I believe that I would need to send the signal as well through the video card, it would need to have additional audio-in functionality like for example with a S/PDIF cable ?

2. My msi card does not have an additional audio in connector, but it does have 2 x Dual-Link Dvi. Would the mic work, if I connect the PC through the DVI output to the LG-TV with the good old RGB cable & then, connect the motherboard with a S/PDIF cable to the back of the LG ?

3. Is HDMI connection only for output, and no input ?

Don´t know if it makes sense to get an additional Sound Card for this purpose, a budget one.

If HDMI is blocking the possibility of recording, I would switch then just the cables whenever I need them for VOIP or gaming.

Thank you all for reading my and thanking in advance for any inputs.
Kind regards,
Ken

Ken, nicely written post.

I think you're giving HDMI more credit than it deserves with your problem. HDMI is very simply a method to send audio and video from one component to another. It is secure (or at least it's supposed to be) and works completely in the digital domain.

HDMI is sending information from one component to another, in this case would be HTPC to TV. It would not be used within your computer although those components must be protected with the HDCP encryption scheme.

You microphone is likely plugging into the motherboard. The microphone is then converted to digital by a D/A converter. The digital signal is then sent to the O/S using the audio driver and then modified by the O/S and the applications. The output is then either converted back to analog and sent to the analog audio outputs of the mother board *or* in digital form the output is read by the video card and then encoded into the HDMI stream. The HDMI stream contains both video and audio as part of the same stream (not separate).

So, the odds of it being an HDMI problem when you get other audio is not likely.

To troubleshoot, do the following:

1) Check that your microphone is working. Use another device to verify the microphone function.
2) Confirm that the input has "microphone level" selected. Microphones have a very low audio level compared to line level (such as an iPod player output). So extra circuitry is usually included to boost the level. If this is not selected, the mic level will be so low that you might not think it is working.
3) Check the audio applets in the O/S. Many of them have microphone level indicators. If you have no indication of levels there, you certainly won't get any audio output further down.
4) Try recording with the microphone with a sound editor. If you can't record any audio then you won't get any audio output either.

All of that is before HDMI even touches the signal. The one HDMI-related item is that some video boards require a jumper to be set to enable audio over HDMI. You might want to check your video board's owners manual to see if that is required for that board.

The HTPC section of the AVSForum may also provide some help.
http://www.avsforum.com/f/26/home-theater-computers

To answer your last question, the audio and video on HDMI are one way (source to sink). The different types of control information flow in both directions. Audio can also go from sink to source using the Audio Return Channel (ARC), but that has limited uses and should not be involved with this problem (and is likely disabled from your description).

Re-reading your post again, I believe this is all happening before HDMI. It's either driver problem or a routing problem. HDMI will not prevent you from recording using the microphone. It hasn't even seen the signal yet.
Good luck!
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post #3 of 4 Old 03-21-2013, 02:36 PM - Thread Starter
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Hi alk3997,
first of all thank you for your prompt answer:)
I was a bit busy these days, couldn't reply earlier.

It´s good to know that HDMI supports recording input, with this I´m 100% sure then, that the problem must be found elsewhere.
I tried like 5 or 6 headsets, all work on my wife`s laptop, but not on my htpc...sigh...

I still got a few things to test, like checking the connectors, too tight screws on motherboard, cables hanging around behind the TV, maybe the chip is getting too hot....things that could cause any kind of interference...
One thing though I noticed is when i "listen" to the device....I hear like a terrible scratching, like the ultrasound noise from an unborn baby.
Anyway, I'll still have stuff to do before I can say that it's a HW issue.
Maybe it´s just some software thing, I really hope so - I'll keep patiently trying.

Thank you also for the htpc section link, I'll check it out.

Kind regards,
Ken

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post #4 of 4 Old 03-21-2013, 02:54 PM
 
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Quote:
Originally Posted by K3npachi View Post

...

One thing though I noticed is when i "listen" to the device....I hear like a terrible scratching, like the ultrasound noise from an unborn baby.

....
Kind regards,
Ken

That was a good clue. If you are hearing scatching, that is usually the result of a large amount of overmodulation. In other words, the mic levels are tuned way too high. That you are hearing something could be a good sign...

Or, the problem could also be caused by a IRQ problem. If it is an interrupt problem you can go into device manager and see if you have an "unknown device" or if any of the IRQs are causing a conflict. That isn't easy and unfortunately, the manual ways to fix that are limited now (the system shouldn't allow that to happen).

So, two things to look at.
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