Several 5.1 Surround Issues

Question

So I have a few issues here, and I only care about getting 1 answer.  I'd like to point out that none of the issues I am getting exist in Windows.  I guess pick whichever of the following you feel most comfortable with:
1.  Games that are not playing in 5.1 analog surround
2.  No surround playback in HDMI
3.  No surround playback in SPDIF
1.  Games that are not playing in 5.1 analog surround
Since ALSA is probably the most painful thing I've ever tried to configure, I installed pulseaudio to set up my analog surround setup.  This has pretty much worked fine - I can use "speaker-test -c 6" and AC3 files in VLC, and I can hear all the channels play the audio they're supposed to.  The game "Amnesia: A Machine for Pigs" also appears to get surround working, though I had to delete the libopenal.so.1 that it ships with (otherwise it's quadrophonic stereo).
However, I've noticed that's pretty much the only game I own that is playing in true 5.1 surround.  From what I heard, Valve games on linux are known to not work in 5.1, and according to one of the developers of Witcher 2, it is a proven fact that they do not have surround working, but it is being looked into.
However, Borderlands 2 is the next priority on my list, and that appears to only have quadrophonic stereo.  It played with full 5.1 surround in Windows.  Surround sound is the ONLY thing preventing me from ditching this game on Windows.
There are other games that seem to have the same issue as BL2 but they are a lower priority to me.
2.  No surround playback in HDMI
I am using the open source radeon drivers, but according to pulseaudio, I get ACT, DTS, EAC3, and MPEG support via HDMI audio.  I can play stereo audio files just fine.  However, if I try playing a .ac3 file in VLC, nothing happens.  According to pavucontrol, there is no sound playing whatsoever.  I can try selecting the device from the audio menu, and it just ignores this.  I tried stopping PA and select ALSA HDMI0 from the audio source in VLC and still doesn't play anything (except stereo files).
I can't remember how I did it, but there was a way where I got my receiver to acknowledge the 5.1 surround channels, but, it still didn't play any audio.
But before I even attempt to fix this, does anybody know for a fact if you get TRUE (meaning, not quadrophonic stereo) surround with games via HDMI?  I don't care about setting this up if only VLC is the only program I have that can take advantage of this.
3.  No surround playback in SPDIF
Just to clarify, if PA is uninstalled, I can get surround playback, but only in VLC.  With PA installed I can play stereo audio just fine but .ac3 files in VLC will not play, and much like my HDMI experience, pavucontrol says there is no sound playing.
I already know that in Linux there's basically no chance of getting SPDIF to work with most games, since there is no option for live DD/DTS encoding.  But, there's a chance that some games do support this, yet I'll never know if PA keeps "muting" AC3 tracks.  Also, my surround receiver supports Pro Logic, Dolby Digital, and other features that really help enhance stereo audio.  You can't get these features in analog.  That being said, I would like to be able to have SPDIF and 5.1 analog output simultaneously, and I can switch between the two based on my current needs.
Last edited by schmidtbag (2014-11-15 05:09:39)

Answer 1

schmidtbag wrote:quadrophonic stereo
See post and technical explanation:
One drawback of surround sound which can lead to problems is that the channel assignment is not standardised (except in the sense that the great thing about standards is that there are so many to choose from). Four channels can represent either 3.1 surround sound (left/right + centre + subwoofer) or 4.0 surround sound (front left/right + surround left/right). Similarly, there are two different conventions for 5.1 surround sound, one upward compatible to 3.1 and one to 4.0. In the first case, the channel order is front left, front right, centre, LFE (low frequency effects = subwoofer), surround left, surround right; in the latter case front left, front right, surround left, surround right, centre, LFE. The latter configuration is the standard under Linux, while the former is common on computer illiterate systems (guess which OS that is...). But reportedly some games assume M$ channel order even under Linux, with the effect that voices of characters behind the player come out of the centre speaker. I do not know about 7.1 channel assignment, but I expect there are the same two configurations, with rear left and right being the last two channels in either case.