HTPC HDMI crackling audio and no 7.1 HELP! - AVS Forum
HDMI Q&A - The One Connector World > HTPC HDMI crackling audio and no 7.1 HELP!
velocitydreamer's Avatar velocitydreamer 07:32 AM 03-13-2012
First off, thank you to anyone who can lend a hand... all helps appreciated, whether the advice works or not.
I am currently using Windows 7 Ultimate 64bit and I have an ASUS p5q and am running a power color hd4870 1gb. I installed the HDMI 2.67 Realtek audio driver and the latest ati catalyst 12.2. I am currently using the dvi-to-hdmi adapter and running it directly into my 7.1 receiver, and then out to my tv. There are two problems I run into. First, after a short bit, I start getting a random/sporatic popping/crackling sound that happens about once every 2 seconds throughout every speaker in the system. I've heard of such an issue, but never really found any resolution that worked. Second, I CANNOT get an HDMI driver that will show 7.1... I've found 5.1 through the ati audio driver, but everytime I go into the windows speaker configure (and the realtek driver, though the realtek driver doesn't actually work and only shows stereo in configure speakers) I only have the "stereo, quadrophonic, and 5.1" options... this system is perfectly setup for 7.1, speakers and all... there's no reason for it not to work. So, when I set it to 5.1, I click next and the side speakers are greyed (might be rears... SHOULD be rears)... so yeah, objectives: get rid of crackling sound and enable 7.1. If I can remedy these two problems, I will be in heaven All help is greatly appreciate guys & ladies. I really want to find a resolution...

alk3997's Avatar alk3997 08:40 AM 03-13-2012
Quote:
Originally Posted by velocitydreamer View Post

First off, thank you to anyone who can lend a hand... all helps appreciated, whether the advice works or not.
I am currently using Windows 7 Ultimate 64bit and I have an ASUS p5q and am running a power color hd4870 1gb. I installed the HDMI 2.67 Realtek audio driver and the latest ati catalyst 12.2. I am currently using the dvi-to-hdmi adapter and running it directly into my 7.1 receiver, and then out to my tv. There are two problems I run into. First, after a short bit, I start getting a random/sporatic popping/crackling sound that happens about once every 2 seconds throughout every speaker in the system. I've heard of such an issue, but never really found any resolution that worked. Second, I CANNOT get an HDMI driver that will show 7.1... I've found 5.1 through the ati audio driver, but everytime I go into the windows speaker configure (and the realtek driver, though the realtek driver doesn't actually work and only shows stereo in configure speakers) I only have the "stereo, quadrophonic, and 5.1" options... this system is perfectly setup for 7.1, speakers and all... there's no reason for it not to work. So, when I set it to 5.1, I click next and the side speakers are greyed (might be rears... SHOULD be rears)... so yeah, objectives: get rid of crackling sound and enable 7.1. If I can remedy these two problems, I will be in heaven All help is greatly appreciate guys & ladies. I really want to find a resolution...

First of all, you're probably in the wrong forum. The HTPC forum would probably be of more help since none of what you described is an HDMI issue.

I suspect your first problem is a driver issue or interrupt issue, although interrupt issues like that should have gone away with modern boards. I'm not sure if I can help you with that issue.

The second issue requires some background knowledge. On the back of most motherboards (these days) are 7.1-channel analog outputs. These ports have a dedicated audio output for each audio channel - actually usually done in pairs (front channels, center/LFE, surround channels and rear channels). So sending out a 7.1-channel signal, in this case, is just a matter of the audio board routing the right signal to the right port. Very simple.

Now when you send 7.1-channel output to the HDMI output, that audio has to be encoded with the video into essentially a single output stream that goes across the HDMI cable. There are no dedicated audio lines - it's all a digital stream.

In order to do that the audio needs to be encoded into a format that can be sent over the HDMI cable and then decoded on the receiver side. With surround sound for many years, this encoding could only be done as a Dolby Digital or DTS output. Dolby Digital and DTS were 5.1-channel outputs, with the exception of the (unfortunately) rarely used DTS-ES (6.1) and Dolby Digital EX (a 5.1-channel with a rear channel matrixed into the surrounds). LPCM was usually reserved for 2-channel at this time.

Along comes Blu-Ray and adds dedicated 7.1-channel output in the form of Dolby TrueHD and DTS Master Audio (DTS-MA). In addition, LPCM can be used to send 7.1-channel audio over HDMI. So, those are the options for true 7.1-channel audio.

Now to get this across the HDMI cable, the sink (your receiver) has to tell the source (the HTPC) that it can support 7.1-channel. So you need two things - an HTPC that can output 7.1 and a receiver that reports it can accept 7.1-channel audio. The 7.1-channel audio can be in the form of LPCM, 7.1-channel Dolby TrueHD (not Dolby Digital) or 7.1-channel DTS-MA (not just regular DTS). If you can't output those, then no true 7.1-channel unless you use the HTPC's analog audio outputs. To use the analog 7.1-channel audio, you simple need a receiver that has 7.1-channel analog inputs.

From your append, it appears that the HTPC's drivers do not support sending 7.1-channel audio over HDMI and would instead use a 5.1-channel signal (what format?) and allow the receiver to derive the back surround channels from the surround channels. The other thing you need is a Blu-Ray player (or game software) that can support 7.1-channel ouput over HDMI. Basically if your source doesn't output 7.1-channel, you can setup the rest of your system perfectly and you still won't get 7.1-channel audio output.

Here's an article about 7.1-channel audio over HDMI:
http://www.anandtech.com/show/2622

Hope that helps. There is a very active HTPC forum on the AVS Forum who can probably help you with the driver issues.
velocitydreamer's Avatar velocitydreamer 09:38 AM 03-13-2012
awesome, thanks Andy! Yeah, the HD4870 card supports a 7.1 setup, and you can set it up, regardless of your output (though you won't have anything through the channels unless you have a source with the channels) and therein lies my problem... setting it up for 7.1 I've had this machine before with it 7channel LPCM I think it was, but had to restore it. I have no clue why I can't get it to work, but yes, i believe the channel issue is related to the drivers... however, the crackling, the only thing I haven't tried that I've seen is changing the pci-e latency.
alk3997's Avatar alk3997 11:19 AM 03-13-2012
For better or worse, you are not the only one with the crackling sound. If I understood right, the causes were reported to be some type of fan interference or maybe overheating.

http://forums.guru3d.com/showthread.php?t=328263

I also did a Google search on the problem. Not surprisingly this thread already shows up in the search.
velocitydreamer's Avatar velocitydreamer 04:30 PM 03-14-2012
I think I've solved the crackling problem for me at least, I uninstalled my audigy driver, realtek, and ati audio drivers entirely, installed the realtek 2.67 driver, rebooted, disabled onboard audio entirely in the bios, and booted... viola, it works.......... ONLY up to 5.1! -.- so NOW, I have to try and figure out how to configure 7.1
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