Surround sound through HDMI

Bill Turnip · 26 Dec 2020 at 11:29

As the title suggests, I'm trying to get a surround sound output via HDMI - I've read quite a few conflicting threads about this and whether it is possible, but don't feel anywhere near the answer.

My setup is a PC in the office, connected to a regular monitor via Displayport on the GPU, and to the TV in another room via HDMI 2.0 from my GPU. The setup on the monitor is not an issue (the motherboard connects directly to studio speakers in the office) and works well. The surround speakers are connected from the TV to a Sonos Playbase via optical, and as far as I can tell all sound processing via the TV is turned off, and should just be passing through the signal received by HDMI. However, the app is telling me that the signal being received is only Stereo PCM 2.0. When testing window sounds, if I select speaker setup to surround, I can get test output on Center front, left and right, but no output from the rear speakers or subwoofer. if I change the output to Quadrophonic, then the rear speakers can work, but still no output from the sub.

The HDMI port I am using is definitely 2.0, and I am confident that the cable (20m, but buffered) is working correctly as the TV is able to display a 4K, 60fps image with HDR enabled. Does anyone know of a way to ensure that the sound being transmitted is 5.1, or is this not possible? I appreciate that not everything will be in 5.1, but I would like it to be possible where applicable, and am running out of ideas of things to try. It is entirely possible I'm missing the bleedin' obvious.

Let me know if any more information would be useful, and thanks to anyone that is able to try and help!

Grimley · 26 Dec 2020 at 19:08

If you are using Windows 10, Control panel, select sound. (Speaker icon) set the HDMI output if its not greyed out to default. There should be a button for speaker setup (Configure) its set to stereo by default. Set 5.1 as default & you should be able to check it by testing the speakers in the dialog box. Bearing in mind that windows will detect all sound outputs including the onboard HDMI of your motherboard or GFX card if it has one, so pick the right one. Also check to see if you have all the hardware drivers up to date before starting.

Bill Turnip · 26 Dec 2020 at 19:39

Cheers for the reply - The drivers are fully up to date. I think I have taken those steps correctly (not at pc right now, but will check later), but when I get to the configure box I can select 5.1, however the sub test produces no sound. I can use hdmi to transfer sound, just not a 5.1 signal.

Grimley · 26 Dec 2020 at 20:28

Should do if its set to default & the 5.0 out of the 5.1 works.

Bill Turnip · 27 Dec 2020 at 10:30

I have checked the above steps and I can select configure to set 5.1 as default. However, when testing the speakers, it shows sound waves coming out of the rear left, right and sub speakers with no actual sound output. This is the step I was talking about in my original post, though it's good to have the steps I've taken already confirmed. The separate app I use for the Sonos shows that it is receiving a Stereo PCM 2.0 signal, even if the speakers are set to 5.1. I'm wondering if the pass through on the TV is the issue, and will move my PC to test this later.

Bill Turnip · 27 Dec 2020 at 12:31

OK - I have moved my PC to the front room to test, and have found that if I connect with optical cable direct to the playbase, I can select Dolby Digital 5.1 and everything works as expected. For the optical output, if I go to Digital Output>Properties>Supported Formats, Dolby Digital is a choice I can select and test, and everything is fine.

Doing exactly the same using the HDMI output, I cannot select Dolby Digital to test, although it is listed under "Encoded Formats". I guess the issue is with the pass-through on my TV in which case...