Bitstream via HDMI from nVidia or AMD GPUs

miggyboys

I've only used VLC for watching MKV video files - I've had Jriver and PowerDVD suggested to me as two applications that allow what you're saying, which I'll try. I've heard of WASAPI and ASIO before, having read they allow high audio quality from Windows OS but never looked into how they work or can be used.

However, I'm also very interested in bitstreaming sound from the games I play, which I don't know is possible.

Thanks for your help so far.

next010

A simple way to test the output;
Download MPC-BE
* click view->options
* select audio and under audio renderer select the HDMI output.
* select internal filters
* click on audio decoders tab then click on audio decoder configuration
* under pass-through tick the box for everything bar encode to AC3.

Now play a video in MPC-BE, if the Dolby/DTS lights come on in your sound system then it is bitstreaming the audio, if it says PCM then either what Nvidia said is somehow correct or there is some other configuration problem.

If you select under audio renderer->mpc audio renderer you can mess around with WASAPI and exclusive modes but the above settings should normally pass the audio.

As to games audio I've never looked into it much but there is a lengthy up to date FAQ on it here that may be of some help, they have a step by step setup guide.

Trollslayer

I use Windows 10, a GT1050 and an Onkyo NR828 plus Kodi.
Passthrouth (that's bitstream) works fine.
The audio format indicators on the 828 works as expected.
This is using the Directsound device listed.

EndlessWaves

Bitstreaming is transferring a pre-recorded track without uncompressing it first, but game audio is created on the fly and is uncompressed from the beginning.

Game audio can be compressed and this is sometimes done for S/PDIF due to its limited bandwidth (typically a lossy compression to enable surround sound rather than to improve quality) but that's not usually referred to as bitstreaming.

Likewise as a general option bitstreaming doesn't make a lot of sense. Because it requires exclusive control of the sound output it means only one program can bitstream at a time. It works for watching a film but it would mean you'd only hear the youtube audio when you were looking at that website. As soon as you switched to a different tab or program it would stop and the new active window would be bitstreaming instead.

It makes much more sense to let programs request it when required.

ChuckMountain

Yes that's the reason you generally don't get bitstreaming in games.  Some games can use Dolby Digital Live or DTS Connect but that's not really needed these days.

As others have mentioned if the game sends PCM sound this is uncompressed sound (via the GPU) and can have multi channel as required.  This will be as good if not better than regular DD, DTS.

Dolby Digital and DTS are compressed so they would uncompressed to PCM to actually do something so if that was the case your PC would have to compress it for your amp to then uncompress it again.  That would be going from lossless to lossy compression.

HD versions are lossless compressed but the game won't sound any different if you could encode and then bitstream.

The reason DTS vs DD can sound different is down to the mixing of the tracks as well as the compression.  No one is mixing the game track in the same way so long as you get the uncompressed sound to the amp that's the best way.

Trollslayer

DD and DTS are lossy, DTS Mater is lossless, all are compressed.

ChuckMountain

Yes sorry what I meant is the DTS Master is lossless compression

miggyboys

Thanks to andy1249, Trollslayer, next010, EndlessWaves and ChuckMountain! Next010, the link to PC Gaming Surround Sound Round-up is fantastic for gamers and really useful.

I don't like doing things without understanding how they work, hence all my questions. I'm now successfully bitstreaming blu ray films and audio using JRiver and it's all confirmed on my Yamaha YSP-2200 sound bar which is great. Games are playing their PCM files in 5.1 and I'm now hearing extra detail I didn't hear before.

I only have one issue now. I cannot get the nVidia GPU to output audio via HDMI to my Yamaha YSP-2200 soundbar and send video via DVI directly to my HP monitor. Why do I want to do this? Well because when I use only HDMI for audio and video to the soundbar and then use HDMI out from the soundbar to my HP monitor, the picture is grainier and worse as it's passing through the soundbar.

If I plug up using both HDMI and DVI, my screen goes a solid light blue colour (not BSOD). If I remove the DVI cable from my monitor (leaving it still plugged in my GPU) and plug in to my HP monitor the output from my sound bar (HDMI to DVI cable), it works.

N.b. I previously (up to one week ago!) used DVI out from my GPU to my HP monitor which worked fine and for sound, I used a USB DAC plugged into active stereo speakers.

Any suggestions?

ChuckMountain

Does the sound bar overlay a volume display on the picture when passing it through as it sounds like it is processing  the picture rather than just passing through.  Any options to switch off?

As for blue screen you should be able to do what you want.  Are you seeing an extended desktop?

What version of Windows are you running.

Have you tried the Windows and P key to toggle displays?

miggyboys

Hi ChuckMountain

There's no volume display on screen and I can't see any options to enable passthrough of video / to switch it off. I only have one monitor and don't use extended desktop. I'm on Windows 7 64 bit SP1. Should Nvidia GPUs automatically detect that various outputs are plugged into audio devices and displays? The Nvidia control panel leaves a lot to be desired. It should give a user control and options for the HDMI / DVI / Display ports.