Issues with Dolby Digital 5.1 output over HDMI

I posted this over on the Nvidia GeForce forums as well, but I know there are some super-smart folks here and I'm hoping someone here might have some thoughts on the below as well.

PROBLEM:
I am no longer getting Dobly Digital 5.1 output to my soundbar in games. With the exact same setup, this worked just as recently as a few weeks ago. DD 5.1 output for movies does still seem to be working correctly via DVD. I haven't tried a video file with DD 5.1 encoding just yet.

MY SETUP:
A gaming PC with a MSI GTX 970 4G output via HDMI to a Vizio E500i-B1 HDTV. The TV is connected via optical to my LG NB3530A soundbar. Essentially, it's GTX 970 >>HDMI-->> TV >>Optical-->> Soundbar. I realize right off the bat this may be a red flag to some folks, but my TV DOES support DD 5.1 output via the optical connector. I'm using this exact setup on my Xbox One with Optical Audio turned off (forcing it to use the audio signal from HDMI) and no optical cable connected directly to the Xbox One with no issues.

ADDITIONAL INFORMATION:
Just yesterday I noticed I was no longer getting DD 5.1 ouptut to my soundbar. Unlike most receivers, there is no DD or DTS light that illuminates when the soundbar is receiving a multi-channel audio signal. You can however push the INFO button on the sounbar remote to see what kind of signal it is currently receiving. It had been a week or so since I had done any gaming with my PC, and I noticed that the audio in Aseetto Corsa was sounding a bit hollow and lifeles. I grabbed the remote to check what the soundbar was receiving, and sure enough, it was only outputting PCM 2.0. Checked a few other games (namely Batman Arkham City and Dirt 3) and neither of these games were outputting in DD 5.1 either.

I am absolutely, 100% sure that I was getting DD 5.1 output to the soundbar as recently as a week or two ago. I know this because when I was shopping around to upgrade my audio setup on the cheap, I wasn't sure exactly how a soundbar with only optical was going to work with this TV (which was relatively new to me at the time). Before deciding to keep the sounbar, I made sure to verify that I was receiving DD 5.1 over optical, which I know can be a bit of a crapshoot at times, at least with many older TVs. Turns out, had I looked at the manual for the TV, I could have confirmed this beforehand, as it is very clear in the manual that multi-channel audio output via optical (compressed only I'm assuming) is supported by this TV. Check out this excerpt from the manual for confirmation:

http://i.imgur.com/UZscCq4.png

I'll re-emphasize, I'm 100% sure the setup I've described here was outputting multi-channel audio to my soundbar just a few weeks ago. To the best of my knowledge, nothing has changed with this setup aside from perhaps some Windows Updates. It looks like I did update my Nvidia graphics drivers back on 12/5, but I'm pretty sure it was working even after that was done, but I honestly can't be 100% sure about that. Uninstalling and then rolling back to an earlier driver is next on my list of things to try. Not sure if the HD Audio driver changed between the current driver and the one previous, but I figure it's worth a try.

TROUBLESHOOTING:
A lot of this is basic, simple stuff, but knowing that this has worked recently, I was grasping at straws. Here's what I can think of that I've done:

• Verified TV is outputting in Bitstream on all inputs.
• Reset soundbar and TV and again verified audio it outputting bitstream on all inputs.
• Verified all connections by unplugging and reconnecting HDMI and optical cables.
• Ran Display Driver Uninstaller in Safe Mode and reinstalled current NVIDIA drivers once rebooted.
• Played a DVD via Windows Media Player. This one perplexes me, because DD5.1 output works here! When a movie is playing, the soundbar indicates it is receiving a DD5.1 signal just as I used to see while gaming.
• And the big one, a clean Windows 7 install. I grabbed an extra hard drive and installed Windows 7, updated all device drivers, and updated Windows. Installed Steam and tried Assetto Corsa again, but still no dice.

There may be a few other things that I've tried as well that I'm forgetting since I've been playing around with this for so long now. But at this point, I don't have much else to try. I want to try to roll back to an older set of drivers this evening and see how that goes. And as unlikely as it is, I'd like to rule out any issues with the soundbar as well, so I'm going to try directing the optical output from the TV to an old AV receiver I have that supports DD 5.1 (but no HDMI input unfortunately).

Any input or suggestions on what might be going on here would be greatly appreciated!

I have a few matters possibly explaining this:

A) Games AFAIK have never bitstreamed Dolby codecs. Game softwares only output PCM audio to the audio soft/hardware (AFAIK). You're getting PCM at the soundbar because that is what the TV is getting, because that is what the GPU is outputtting, because at the software source you're generating PCM.

TOSLINK optical being a 3-decade old monstrosity that should have been deprecated a decade ago cannot handle 5.1 channels of PCM.

2) Your game selections may not even output 5.1 channels even in PCM. Lots of big titles (Mass Effect series) only do stereo.

The problem with the above relatively simple explanations is when you say

pcguru83 said:

PROBLEM:
I am no longer getting Dobly Digital 5.1 output to my soundbar in games. With the exact same setup, this worked just as recently as a few weeks ago.

Click to expand...

As, in gaming with an optical connection, given the above problems this should never have worked...unless before you were running some PCM-DD live bitstreaming conversion software on your machine or GPU-drivers that you suddenly turned off or got turned off (read broken) with an update. DVDs should always do surround sound fine on any hardware, if DVDs don't work with surround it means your hardware is broken (or you didn't select the right audio track). I doubt you have a hardware problem with your soundbar-more likely a configuration problem on your computer that got broken by an update.

Skripka said:

I have a few matters possibly explaining this:

A) Games AFAIK have never bitstreamed Dolby codecs. Game softwares only output PCM audio to the audio soft/hardware (AFAIK). You're getting PCM at the soundbar because that is what the TV is getting, because that is what the GPU is outputtting, because at the software source you're generating PCM.

TOSLINK optical being a 3-decade old monstrosity that should have been deprecated a decade ago cannot handle 5.1 channels of PCM.

2) Your game selections may not even output 5.1 channels even in PCM. Lots of big titles (Mass Effect series) only do stereo.

The problem with the above relatively simple explanations is when you say



As, in gaming with an optical connection, given the above problems this should never have worked...unless before you were running some PCM-DD live bitstreaming conversion software on your machine or GPU-drivers that you suddenly turned off or got turned off (read broken) with an update. DVDs should always do surround sound fine on any hardware, if DVDs don't work with surround it means your hardware is broken (or you didn't select the right audio track). I doubt you have a hardware problem with your soundbar-more likely a configuration problem on your computer that got broken by an update.

Click to expand...

That's some pretty interesting stuff there, thanks. But I think this now makes even less sense to me then it did initially. First off, with regards to your second point, I know for sure that the primary game I'm concerned with (Assetto Corsa) does output in 5.1 channels, so that shouldn't be the issue. Not sure about the other two I mentioned though (Batman: Arkham City and Dirt 3), but both are pretty recent so I'd have to think they do.

But I have to be honest you've got me doubting myself a bit though now based on the last part of your comment. With what you've shared on how games output multichannel audio, it sure does seem that it never should have worked in the first place. I've never done anything with bitstreaming conversion software, so that's definitely not it. Is multichannel PCM to Dolby/DTS conversion something that some GPU drivers do when processing audio over HDMI? I do still want to try to downgrade my Nvidia drivers to the previous release and see how that goes, so if this is something GPU drivers that support HDMI audio do, that might be a possibility.

That being said, I found this interesting little snippet from Turtle Beach (here) which does seem to validate your thoughts above about multichannel audio output in games:

Turtle Beach Website said:

If you're trying to play surround sound from your PC to your headset and you're only getting Pro Logic II (not Dolby Digital) make sure that you are not trying to get Dolby Digital transmission from PC games. Most PC games use "multichannel LPCM" encoding for their soundtracks (Linear Pulse Code Modulation), not Dolby Digital encode/decode. Older (pre-2009) PC games do not include Dolby Digital Live processing to convert their LPCM audio to Dolby Digital inside the game, so only PCM (stereo) audio data will be sent through the PC sound card's S/PDIF Out (optical digital output).

Click to expand...

That's a bit perplexing. They seem to indicate that most games do use multichannel LPCM. But then they turn right around and say that most older games (pre-2009) don't use Dolby Digital Live processing to convert to a compressed encoding on the fly. The way it's worded kind of implies to me that using Dolby Digital Live is now pretty common most modern games (or at least this isn't an issue in most modern games).

pcguru83 said:

That's some pretty interesting stuff there, thanks. But I think this now makes even less sense to me then it did initially. First off, with regards to your second point, I know for sure that the primary game I'm concerned with (Assetto Corsa) does output in 5.1 channels, so that shouldn't be the issue. Not sure about the other two I mentioned though (Batman: Arkham City and Dirt 3), but both are pretty recent so I'd have to think they do.

But I have to be honest you've got me doubting myself a bit though now based on the last part of your comment. With what you've shared on how games output multichannel audio, it sure does seem that it never should have worked in the first place. I've never done anything with bitstreaming conversion software, so that's definitely not it. Is multichannel PCM to Dolby/DTS conversion something that some GPU drivers do when processing audio over HDMI? I do still want to try to downgrade my Nvidia drivers to the previous release and see how that goes, so if this is something GPU drivers that support HDMI audio do, that might be a possibility.

That being said, I found this interesting little snippet from Turtle Beach (here) which does seem to validate your thoughts above about multichannel audio output in games:

That's a bit perplexing. They seem to indicate that most games do use multichannel LPCM. But then they turn right around and say that most older games (pre-2009) don't use Dolby Digital Live processing to convert to a compressed encoding on the fly. The way it's worded kind of implies to me that using Dolby Digital Live is now pretty common most modern games (or at least this isn't an issue in most modern games).

Click to expand...

The Turtle Beach blurb sounds like some late night editorial proofreading confusion.

They're careful to say "most" in the same manner I said "AFAIK"...because I honestly do not know of any game that bitstreams DDL surround sound to start with-AFAIK they all only bother doing LPCM and leave it to the OS/soundcard to do more, but that doesn't mean there's that one bizarre title out there that actually does so. And with HDMI proliferation DD codec support is becoming less and less of a priority than it ever was-because HDMI can handle 5.1 channels of LPCM just fine so why bother with supporting and licensing the use of ultra-lossy codecs (which is what DD and the like are).


Only two real possibilities that I can think of in your case:

A) You had PCM-DD conversion going on somewhere in your device chain whether you knew it or not. It isn't unheard of, heck my soundcard in my sig rig does it with the right boxes checked. Maybe your soundcard (GPU) drivers were doing it-it doesn't take much of any modern compute power, although the conversion does add a good bit of latency. That it no longer works means a device driver was updated or somehow settings were lost.

and/or

2) Your soundbar or device settings or device drivers somewhere were configured to upmix 2.0 stereo LPCM input to faux-"surround sound". Which can either sound "not bad" or terrible depending on what you're listening to and how attuned your ears are and how well calibrated your speaker delay timings are to your physical location relative to the speakers. Hell, many recent movies have mixing errors in their 5.1 tracks that you can spot with a good sound setup. This not working again would mean a loss of settings or driver configuration.


Maybe someone else has some other ideas, but that is all I'm coming up with this Monday morning with a bunch of coffee.

Skripka said:

2) Your soundbar or device settings or device drivers somewhere were configured to upmix 2.0 stereo LPCM input to faux-"surround sound". Which can either sound "not bad" or terrible depending on what you're listening to and how attuned your ears are and how well calibrated your speaker delay timings are to your physical location relative to the speakers. Hell, many recent movies have mixing errors in their 5.1 tracks that you can spot with a good sound setup. This not working again would mean a loss of settings or driver configuration.


Maybe someone else has some other ideas, but that is all I'm coming up with this Monday morning with a bunch of coffee.

Click to expand...

I'd be inclined to think this is happening. I've been using HDMI audio with nvidia cards for years to output 5.1/7.1 pcm to my receiver. I can confirm that nvidia cards are unable to encode Dolby Digital or DTS signals, and can only generate LPCM multichannel signals. Of course, they can bitstream these signals just fine, they just can't create them. Although the software has been around for years to encode in real time, there would be licensing involved that Nvidia would have to pay for to allow such a feature to be included in their drivers.

If you were actually getting true 5.1 in your pc games, it would have been because your computer passed a 5.1 lpcm signal to your tv, which then encoded it into a DD or DTS stream and passed it to your receiver. To test, make sure you have a 5.1 speaker configuration selected in your hdmi audio properties.

Unfortunately, though, I think the theory that your soundbar was upmixing from stereo may be more likely

But on the bright side, this gives you an excuse to upgrade that soundbar to a model with hdmi passthrough, or a larger receiver