No AC3 Passthrough with Intel ARC A380

[aldamon]

Hi all,

I just installed an Intel ARC A380 GPU in my HTPC and AC3 passthrough will not work. I don't want to use PCM because Windows 10 has a bad habit of resetting speaker config to 2.0 on reboot or wake. I want the receiver to handle everything with bitstream. Any ideas? My 1050 TI did not have this problem so I'm wondering if SiliconDust needs to work on Intel compatibility.

https://imgur.com/a/ZDnwWNw

Edit: My HDHomeRun is the 4K Connect from Kickstarter.

[SpazPlayzz]

Would be interesting to know as well as I too have a HTPC with an Intel Arc a380.

[rikd]

Try removing and reinstalling the latest Intel drivers.
The ARC cards have had lots of issues with Audio and HDMI (as well as display compatibility) since launch
Drivers updates and/or windows updates can fix or break it and Intel is updating the drivers regularly.
Also make sure you have PCIe rebar enabled - yes, even for a 4GB Arc A380!
Intel's drivers require rebar to be enabled for performance and stability.
If you have iGPU and Arc - try disabling the iGPU to force the audio path to the Arc

Ultimately it is up to Intel's drivers to tell Windows what the card supports.
The OS (via the drivers) is telling Apps what is supported.
And if the driver isn't advertising AC3 passthrough capabilities then nothing in the chain gets turned on.
Strongly recommend a post over on the Intel forums for the ARC Graphics.
https://community.intel.com/t5/Graphics ... anguage=en

[SpazPlayzz]

I will try disabling the igpu, but there was just a new update graphics driver update the other day that didn't change anything as far as allowing ac3.

[SpazPlayzz]

Ok disabled igpu no difference or change. Still no ac3. I have a Vizio 5.1 sound bar. My TV is connected HDMI to my PC and my sound bar is connected to HDMI earc to my TV. Any other settings I should check or enable?

[rikd]

Upgrading drivers leaves existing config in place which clearly is incorrect for you.
Delete/Uninstall and potentially do a full clean of the drivers and then reinstall will create a new config and hopefully establish the ac3 passthrough.

If the iGPU also Intel.. Definitely do a complete clean/install.

I assume your TV/Soundbar config hasn't changed since the Nvidia.. so should work. But could be an incompatibility with the TV and GPU. Its up to the GPU to negotiate with the TV through reading the EDID info and matching what it will allow and then updates the OS on capabilities.
The TV will do same to soundbar so it can advertise to the PC what it can support. So any changes there such as firmware or cables can cause an issue also. Some TVs will allow AC3 to it and down mix to stereo, so might be worth just using TV speakers and see if ac3 passthrough works without the soundbar and that u don't have some issue with the TV getting confused.

[SpazPlayzz]

I haven't had anything other than Intel. I was just using the igpu then added the Intel arc ASRock a380 a few months later. However I didn't have a hdhomerun flex 4k until after I had already installed the graphics card.

[rikd]

Ahh
I confused you with the OP. Apologies.

You can check the edid reported by the TV to the intel gpu. There are a few edid readers just a quick Google away.
If not getting AC3 passthrough options is because intel gpu is not getting the info from the TV or is bad config.. latter sometimes can be fixed with a delete and install of drivers.
It is the responsibility of the GPU drivers to report the display info including audio capabilities to the OS for apps to find.
FWIW ARC/eARC are notoriously tricky and can be touch and go to get a complex audio path to work successfully. Is possible because of the ARC connection to the soundbar the TV won't accept anything but PCM from HDMI sources. Again edid check will confirm what the GPU is seeing.

EDIT
Just to add..
what you want to check in the edid is the edid extension - CEA-861
It should contain some audio format codes to indicate what's possible beyond 'basic' audio.

[SpazPlayzz]

Thank you I will check those later tonight or tomorrow.

[aldamon]

AC3 passthrough is working with every other application/player on the computer so it's not necessarily Intel here. I have the latest Intel driver installed clean. Rebar is enabled. I do not have an iGPU. The good news is I figured out what was causing Windows 10 to keep switching back to stereo instead of 5.1 so PCM mode is working fine. Would still like to know what's going on with AC3 though.

[rikd]

AC3 passthrough is working with every other application/player on the computer so it's not necessarily Intel here.

True.
Could be MS - even could be us.
Which Apps work?
Not every App is built the same. Some Apps implement their own EDID reader and bypass the Windows Registry that is populated by the drivers so they can check themselves, others such as ours are constrained in the Windows APIs (there are a few APIs to get the info - not all are permitted for UWAs) we can use - and thus must rely on what Microsoft tells us from the Windows Registry.

Try this.
Open the Sound control panel app. Fastest way is to press windows key, type sound (don't hit enter) - and then select the App

Once open, select 'Playback' scroll down to your display and click 'Properties'

What you want to look at is what is in 'Encoded Formats' under 'Supported Formats' as well as the Max number of channels

If AC3 (Dolby Digital) is not listed then it's likely a driver issue.
If it is listed - then is likely an MS to App problem we can chase up.

Would still like to know what's going on with AC3 though.

Will see what we can find out

[aldamon]

Could be MS - even could be us.
Which Apps work?

The computer with the issue is a HTPC so LAV/ffdshow both pass AC3 fine and the internal filters on VLC, MPC-BE, MPC-HC, Win10 Movies & Videos, and Win10 Media Player all bitstream AC3 fine as well as every other audio format from my media files. I tested basically everything after the A380 upgrade. Only HDHomeRun is currently refusing to pass AC3 on the computer.

[rikd]

Could be MS - even could be us.
Which Apps work?

The computer with the issue is a HTPC so LAV/ffdshow both pass AC3 fine and the internal filters on VLC, MPC-BE, MPC-HC, Win10 Movies & Videos, and Win10 Media Player all bitstream AC3 fine as well as every other audio format from my media files. I tested basically everything after the A380 upgrade. Only HDHomeRun is currently refusing to pass AC3 on the computer.

What does the Sound Panel say for Encoded Audio Formats for that display?

[SpazPlayzz]

In my case properties shows:

Supported Formats:

HDCP-Supported

But Depths- 16 bit, 24 bit

Sample rates: 32.0khz, 44.1khz, 48.0khz, 96.0khz, 192.0khz

Encoded Formats:

Dolby Digital Plus

Dolby Digital

[rikd]

In my case properties shows:

Supported Formats:

HDCP-Supported

But Depths- 16 bit, 24 bit

Sample rates: 32.0khz, 44.1khz, 48.0khz, 96.0khz, 192.0khz

Encoded Formats:

Dolby Digital Plus

Dolby Digital

And when you request the app to do AC3 passthrough do you get the same message as @aldamon in his OP"? - i.e.
"AC3 digital audio passthrough is not available - playing PCM audio"

Or just not getting AC3 on your soundbar?