Displayport to HDMI Adapter - Multi Channel Audio?


#1

Purchased the Displayport to HDMI adapter here:

http://plugable.com/products/dp-hdmi/

I cannot get anything other than stereo sound from this adapter. Using a HDMI connection directly from my video card, multiple sound channel options (and sample rates) are present.

I am curious, does this adapter actually support multichannel audio and sample rates higher than 48khz? Thank you!

!](https://d2r1vs3d9006ap.cloudfront.net/s3_images/1587454/SupportedFormats_inline.jpg?1493080559)](https://d2r1vs3d9006ap.cloudfront.net/s3_images/1587454/SupportedFormats.jpg?1493080559)


#2

It depends on your display, graphics card, and your screen resolution.

Looks like you’re using a HT-R393 AV receiver. What display is connected to that?

The -C suffix might mean you’re using an Nvidia graphics card - which one? (where C might be the 4th possible audio device on the graphics card (possibilities are 0, 4, 8, C) which might possibly be assigned to any one of five displays, only four of which can be used at a time, although I don’t know if AMD or Intel graphics don’t have a similar behavior).

The dp-hdmi adapter “supports pass-through of LPCM/HBR audio up to 8-channels and 192kHz sample rate.”

The AVR HDMI inputs supports “DTS-HD Master Audio, DTS-HD High Resolution Audio, Dolby TrueHD, Dolby Digital Plus, DSD, Multichannel PCM”.

Maybe someone here can tell us if that means there is or is not overlap between those two sets of supported audio formats (I think HBR Audio includes stuff like Dolby TrueHD; I’m not sure if Multichannel PCM is the same as LPCM). It looks like the graphics card’s audio driver can use all the formats (what’s listed after Dolby Digital?), so you need to just figure out why it says only 2 channels, 16 bit, 48 kHz. I don’t have a multi channel device to test this myself. I have 3 displays that all say max channels 2 (General tab says “L R HDMI Digital Jack”). Each display has a different number of supported Bit Depths and Sample Rates. The HDMI displays show more options (even if connected to a DisplayPort port using a passive DisplayPort to HDMI adapter). The DisplayPort display shows one Bit Depth and one Sample Rate like yours. None of mine support any compressed formats (Encoded Formats).

Some audio formats might not be compatible with 4K@60Hz 4:4:4 RGB video (I’m not sure about that). It depends on how much bandwidth is left over for the audio.

Don’t the Encoded Formats allow more than 2 channels anyway?


#3

Hi Alex, thanks for posting! As Joevt mentioned, our DP-HDMI adapter only supports surround audio over LPCM (which should be the same as multi-channel PCM). Would you be able to confirm if this encoding format is being used to transmit audio?

Thank you,

David W.
Plugable Technologies
www.plugable.com/support


#4

Hello David and Joevt! Thank you both for your quick replies.

First, Joevt, excellent detective work on determining the details of my configuration.

I’ve spent more time testing tonight and it appears to be a limitation of the display adapter.

I’m running Windows 10 (1703) and outputting via a Geforce 970 over DP to HDMI. The source of audio varies from games to media applications. The core windows audio configuration (Nvidia HD Audio) itself is unable to be configured for 5.1 when using the DP to HDMI adapter (nor can I specify higher sample rates.)

With the DP to HDMI configuration, I am able to confirm my AVR does not receive a 5.1 signal even if the application generating it uses DTS or multi-channel PCM (both of which it supports just fine over normal HDMI.)

I can speculate that none of my applications nor native Windows 10 sound are encoding via LPCM.

My only guess is the chip in the active adapter is not able to do what I require of it. I will be obtaining a passive adapter to test this theory, as my video card also supports this.

Thanks!


#5

I have read that some HDMI AVR that are set to output audio to a TV may report the audio features of the TV to the video source, which may limit it to 2 channel. I don’t know if that’s an issue with the Onkyo HT-R393.

You many wish to examine the EDID reported to the graphics card, and the ELD reported to the Nvidia HDA codec. There are many EDID viewers for Windows. The ELD is supposed to come from the EDID so it probably isn’t necessary to look at it. If you want to verify that it is the same as the audio information in the EDID then you might need to use a Linux OS like Ubuntu and use this command:
also-info.sh --output ‘also-info.txt’
The ELD is described in the Intel High Definition Audio Specification (available in PDF).

You didn’t say which Geforce 970 you have. Yours doesn’t have an HDMI port? Or it does and that is the HDMI port you tested when you said “both of which it supports just fine over normal HDMI.”? They’re usually HDMI 2.0 in the 900 series cards. The cards should also support DisplayPort dual mode passive HDMI adapters but only HDMI 1.4 because they are DisplayPort 1.2 ports.

GTX 1070 and 1080 cards should have DisplayPort 1.3 or 1.4 which should support HDMI 2.0 dual mode passive adapters but I haven’t tried it. Actually, the specs for the 1070 and 1080 say “DisplayPort 1.2 Certified, DisplayPort 1.3/1.4 Ready” so I’m not sure about their current capabilities, plus existing passive adapters might not be good enough for HDMI 2.0?

Maybe HDMI 1.4 is good enough for your purpose? You didn’t say if you needed any of the HDMI 2.0 features.


#6

Hi Alex, thanks for the reply.

One variable we can try is to see if a firmware update to our adapter helps affect change. I would be happy to send you instructions and the update utility in order to preform the firmware update, if you would like, and I would reach out to you directly via email to do so.

Please let us know if you’d like to try a firmware update and we will prepare the documentation and proceed accordingly.

Thank you,

David W.
Plugable Technologies
www.plugable.com/support


#7

Thanks again for the quick replies gentlemen!

First, Joevt, to answer your questions, the AVR EDID is not a problem; due to how my setup is configured, the TV is not directly connected into the AVR. No pass through of the TV’s EDID would be occurring.

As for my GPU, it is an ASUS STRIX 970 4GB model and has 2x DVI, 1x HDMI 2.0a and 1x DP. As mentioned, the HDMI port works wonderfully to my AVR whereas the DP does not.

To clarify my configuration, I am running the HDMI directly to my TV for 4K HDR10 (My AVR only supports HDMI 2.0 and not HDR10) and a second DP -> HDMI connection into the AVR.

DP dual mode is supported on my card, you are correct that it is Display Port 1.2. The output video resolution is meaningless to me, as it will be a phantom display. I am more concerned with audio fidelity (hence the use of HDMI for bit-stream pass through versus S/PDIF / Optical.)

David, regarding your response. I would be glad to try a firmware update of the adapter to see if that has any effect. If you want to send me the relevant utility I will give it a try! I will also report back tomorrow, as the passive adapter is set to arrive in the mail (also a Plugable device, you guys make good products and your support is superb.)

Thank you both for your time.

Cheers!

  • Alex

#8

So the EDID / ELD must come from the AVR. It’s probably correct, but may be interesting to know what it says about the AVR’s capabilities, and how that compares to the documentation.

A phantom display means you could lose the mouse cursor off the main display? Or do you use display mirroring? If you disable the phantom display, then it also disables the ability to output audio, right?

Although DVI is supposed to max out at 165 MHz (single link), your graphics card may allow HDMI 2.0 to be output from those ports. My Titan X (Maxwell generation, same as the 970) has a DVI-I port that supports 4K@60Hz HDMI with audio (just like the Titan X’s HDMI 2.0 port), Dual Link DVI (165 MHz * 2 = 330 MHz), and VGA. So that might be another option to try for the TV or the AVR. And it might be better, if it does allow HDMI 2.0a like the HDMI port. The DVI-D to HDMI cable is passive, works with either as source, and should work with the DVI-I or DVI-D port. I don’t know if all such cables are rated for those speeds though. If not, then the display or audio may cut out momentarily. In that case, it might be best for the DVI to output the audio, since the phantom display could be set at a low resolution if you’re not using mirroring.

Right, S/PDIF/Optical is an old technology with much less bandwidth/features than the newer HDMI.


#9

A quick update. The passive adapter has resolved the issue. It is passing through the audio without issue. The AVR is picking up the signal and working wonderfully.

Thank you to both Joevt and David for your help on this! It looks like the active adapter’s audio chip simply cannot work with my configuration.

David did send me a new firmware to try on the active adapter. I have not had luck with updating it, but may try in the future. With the passive adapter meeting all my needs I will probably tuck the other one into a bin.

Thanks again and have a great night!

  • Alex

#10

Hey, all, I have this exact same issue. GTX 980 to Onkyo receiver using the same adapter you reference in the original post. Windows 10 only shows 2 channels max for the audio device. Is there a solution for this? I will need 2160 @ 60 hz in the future so the passive adapter is not really a viable solution for me. Thanks in advance.


#11

Hi Daniel, thank you for posting! Since this is an older thread, we’d be happy to assist directly. Whenever you have a moment please contact support@plugable.com and we’ll proceed from there.

Thank you,

David W.
Plugable Technologies


#12

OMG dude. Just go to config in audio, select your receiver and configure it. By default only 2ch are set. You can add all the avaliables by selecting 5.1,7.1, etc. Continue the configuration and apply. Ez pz


#13