Dolby 5.1 mystery

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sjr56stn

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Dolby 5.1 mystery

#1

Post by sjr56stn » Tue Nov 26, 2019 12:45 pm

I have a Windows 7 64bit media PC, which includes a Saphire HD6450 video card, which has AMD High Definition HDMI Audio. This is connected to my TV by HDMI cable, and an optical cable goes from the TV to my Logitech sound system. This always used to provide Dolby 5.1 true surround sound when fed with an appropriate recorded or live TV or DVD source, but something has changed! It took a while to notice this problem, but I suspect a Windows update sometime back might have caused it.
The Windows sound applet now just reports 2-channel stereo for the AMD HDMI audio, but amazingly WMC drives all six speakers when you go to set up speakers and click the test button. But it reverts to stereo as soon as you leave the setup speakers dialogue.
I have updated the HD6450 driver, but it makes no difference to the problem. (And I have then rolled back this driver because it seems to make WMC unstable.)
I have seen quite a lot of stuff online about Win 7 bugs in the sound, but none of the fixes I have tried seen seem to work for me.
It seems to me that Windows 7 only sees a 2-channel sound system, but WMC knows the trick to switch on all the 6 channels but only when you are in the setup dialogue!
Any ideas?
Steve

PS - My Asus P7P55-M motherboard includes Via Technologies sound, but I have disabled this to avoid confusion. (I have tried disabling it in Windows, even disabling it in the BIOS setup, but this makes no difference to my problem.)

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StinkyImp

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#2

Post by StinkyImp » Tue Nov 26, 2019 3:34 pm

sjr56stn wrote:
Tue Nov 26, 2019 12:45 pm
I have a Windows 7 64bit media PC...
Worth 2 cents (or less).

Some years ago I was trying to hook up Sony ARC to a Yamaha sound system. After a few hours of struggling with it, I gave up.

Since then (and on a number of systems) I have used the following cable configuration.

For WMC use:
  • For video -> HDMI cable from PC to TV (no audio).
  • For audio -> Sound outputs on PC to inputs on sound system.
For TV only (from cable or antenna):
  • For audio -> Optical cable from TV to optical input on sound system.
This has always worked for me to provide 5.1 through my receiver even when the signal is in stereo. In those cases it may not be true Dolby, but it's better than stereo from the TV speakers.

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#3

Post by sjr56stn » Tue Nov 26, 2019 4:12 pm

Yes, I can get surround sound from the PC if I use the VIA Technologies HD audio and the analogue cables straight from the PC to the sound system, but then I have to switch the sound system to optical input when I want to just watch TV in 5.1.
That is annoying and, as I said, it used to work fine!

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#4

Post by sjr56stn » Tue Nov 26, 2019 4:25 pm

.. and I really would like to understand how WMC is able to drive the 6 speakers when in the speaker setup menu, when Windows insists that the HDMI audio has only two channels!

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#5

Post by dmagerl » Tue Nov 26, 2019 4:34 pm

Is the auto volume feature enabled in WMC? That converts 5.1 to 2 channel.

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#6

Post by sjr56stn » Tue Nov 26, 2019 5:21 pm

No, auto volume is not set and, as I said, WMC can drive all 6 channels in the speaker setup dialog. It is Windows that insists that there are only two channels.

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Shark007

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#7

Post by Shark007 » Tue Nov 26, 2019 6:25 pm

The TV only has 2 speakers therefore the HDMI connected to the TV sees 2 channels.
The TV (no TV, not just your TV) is NOT capable of passing a multichannel signal from the PC over HDMI to the optical out of the TV.

When using the TV without the PC as the source, you can get multichannel audio sent to the soundbar if the channel has 5.1 audio
Retain your sanity, use Shark007 Codecs

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#8

Post by sjr56stn » Tue Nov 26, 2019 6:43 pm

Thanks Shark007, but it used to work, and WMC can send 6 channel through the HDMI and TV when in the Speaker setup dialog, AND the TV is perfectly capable of receiving and passing through 6 channel digital audio.
If you are saying that something has changed in the Windows audio driver to force 2 channels when it recognises a TV on the end of the HDMI, then that is certainly possible. If so, WMC whilst in the speaker setup dialog, is ignoring this 2-channel restriction.

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#9

Post by Shark007 » Wed Nov 27, 2019 2:15 pm

Shark007 wrote:
Tue Nov 26, 2019 6:25 pm
The TV (no TV, not just your TV) is NOT capable of passing a multichannel signal from the PC over HDMI to the optical out of the TV.
I am not saying something has changed.
I am saying that you are mistakenly believing this worked for you in the past.

For this to work, you would need a direct connection from the PC to the Soundbar.
Retain your sanity, use Shark007 Codecs

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#10

Post by sjr56stn » Wed Nov 27, 2019 2:38 pm

Oh! I am an unreliable witness!
We have a number of music concert TV recordings that we used to watch in 5.1. Now we cannot do so.
We have a number of DVDs and blu-rays that we used to watch in 5.1. Now we cannot do so.
I can assure you that something changed a few months ago.

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#11

Post by Shark007 » Wed Nov 27, 2019 3:39 pm

I am somewhat aged and my information can be aged also.
So, I went and did some searching to refresh my knowledge...
This page is quite helpful for your topic - https://www.rtings.com/tv/tests/inputs/ ... assthrough
"Dolby Digital 5.1 passthrough via digital optical" is a heading of interest on that page.

Bottomline as far as I can tell is that it is a feature that your TV must support.
Retain your sanity, use Shark007 Codecs

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#12

Post by sjr56stn » Wed Nov 27, 2019 4:53 pm

Shark007 - Thanks for the interesting link. I am also somewhat aged (I was learning FORTRAN in 1966), but I shall study it and try to understand it!

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#13

Post by sjr56stn » Wed Nov 27, 2019 5:17 pm

Out LG TV is some 7 years old, and does not appear on the list, but the manual and specification imply that it will pass a digital audio signal through to the optical audio output. All the TVs that are listed seem to pass the Dolby 5.1 through.
And (sorry to be boring) as I keep saying, it used to work! And it STILL WORKS when clicking the test button in the WMC speaker set-up dialog. The 6 speakers sound in sequence, and the little display on the sound system shows Dolby digital. So that proves that the TV is passing the Dolby 5.1 through to the sound system. It just switches back to stereo as soon as you leave that WMC speaker setup dialog.
This has just got to be a Windows 7 issue.

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#14

Post by StinkyImp » Thu Nov 28, 2019 3:55 pm

sjr56stn wrote:
Wed Nov 27, 2019 4:53 pm
I am also somewhat aged (I was learning FORTRAN in 1966)...
Thanks for making me feel young again! I was learning FORTRAN and COBOL in the early 80s and have been feeling the ravages of time recently. ;)

You said that it worked previously. If you haven't made any hardware or cabling changes, have you searched the Event Log for the past few months to see if you have any errors or warnings that might give you any clues as to what may have happened?

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#15

Post by sjr56stn » Thu Nov 28, 2019 4:35 pm

StinkyImp - No I haven't scrolled through the event log. Cannot do that just at the moment. But the crucial point is that the WMC speaker dialog and test button can make it work now! It just reverts to Stereo as soon as you leave the dialog. Perhaps I should use the speaker test button and then immediately look at the event log. I will try that later.

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