Linux 7.1 audio question

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1

New ish to linux.

 

I have a 7.1 reciever that my ubuntu box plugs into.

I can set my audio to stereo, 5.1 and 7.1 in the sound settings.

Inside plex, the normal options are available as well.

 

No matter what the source audio is, linux outputs whatever the sound settings are set to (stereo, 5.1, 7.1)

So if everything is set to 7.1 and the source audio is 7.1 it is perfect (star trek into darkness is amazing in 7.1.) But if the source audio is 5.1/6.1, hell even stereo; ubuntu still outputs 7.1 channels thus the reciever cannot scale the audio out to 7.1 via decoding or whatever.

 

The best way I can describe it is seems the audio is statically mapped to use all 8 channels no matter what.

 

Is there a way that it can dynamically change based on the audio source output? Seems like chromecast and roku do this?

 

As a stop gap I have just set everything to 5.1 and let the receiver upscale it to 7.1 which still works pretty damn good.

So 7.1 audio is getting transcoded to 5.1 (or maybe 5.1 is encoded in 7.1, idk,) then sent to the reciever and re-upscaled...

 

Does this make since?

 

Let me know if this is possible or if I am trying to have my cake and eat it too.

 

Thanks all.

2

My good guess is that your audio is being messed up by pulseaudio...

As you are new..ish to Linux, I have no easy way of explaining what you need to do...plus I hate Ubuntu...

I currently run my PHT on CentOS Linux using ALSA and audio bitstreaming works perfectly well...

It is a bit tricky to remove (or disable) pulseaudio but if you can google and play around a bit you might succeed,

First question I would ask is what type of GPU do you have in your Ubuntu box?

Just keep it in the corner of your mind that you might be doing a few format / re-installs before you get it running the way you want...

This is the fun in the Linux world... :D

3

I know it is pulseaudio, took me a bit to figure out how to get from 5.1 to 7.1. (I learned that dvi to hdmi adapter from my gfx card doesnt support 7.1. I assume its a dvi limitation. Fix by going from hdmi to hdmi.)

I'm not sure what ALSA or audio bitstreaming is, can you explain or provide some links for me to read? I will of course use my googleFu to try to educate myself on it.

My graphics card is a nvidia 560ti.

Not adverse to reformatting. This media pc has been windows 7, ubunutu 12.04, 13.10, steamOS and now 14.04.

4

Okay I got it working.

Bitstream audio to my reciever so that codecs are pass through my receiver which can decode the original source and/or upsample it from whatever to 7.1

I used this guide:

http://linuxg.net/how-to-properly-replace-pulseaudio-with-alsa-on-crunchbag-linux-and-debian-squeeze/

I tried launching the GUI audio controller after but that didnt work, the preferences screen was just blank.

But I went into plex settings and set my audio as the hdmi connected to my onkyo 616 receiver and it works. The menu spits out 2.0 but all videos get pushed out from the original source encode (Dolby, DTS, TrueHD...)

Using an i3 2nd gen chip, micro board. nvidia 560ti gfx running my audio from the mini hdmi in the gfx card to receiver. Ubuntu 14.04

Pasted script incase the linked site ever goes down.

First, kill pulseaudio:

$ sudo killall pulseaudio


Remove all pulseaudio packages:


$ sudo apt-get purge pulseaudio pulseaudio-utils gstreamer0.10-pulseaudio libpulse-browse0 paman pavumeter pavucontrol


Install ALSA:


$ sudo apt-get install alsa-base alsa-tools alsa-tools-gui alsa-utils alsa-oss alsamixergui libalsaplayer0
5

That is the spirit...

Nice to see you got it working the way you want...

6

Thanks for pushing me in the right direction balky.

Now I am trying to get it to work with steam running on ubuntu 14.04, steam cannot find an audio device...

7

What kind of audio device is this? onboard? CPU integrated? GPU integrated?

8

Same pc. nvidia 560ti gpu. I assume most games will not use dolby/dts just use PCM/LPCM. So I dont really care about 'bitstreaming' game audio.

So far I tried reinstalling pulseaudtio to work along side alsa, but that broke plex audio and still didnt work in steam.

9

I've yet to see a situation where the two work side by side... in most cases I have seen, it is either one or the other...

From what I have read, ALSA can be a pain, especially when it comes to gaming because of design complexity... i.e the complexity in ALSA architecture does not make it easy for game writers to integrate sound... which is the reason why games writers prefer to work with pulseaudio

10

I am going to rebuild and see if I can get a side by side going basically by skipping the purge command from step 2 above. If not I guess I can throw in another hdd and just go into a dual boot scenario, HTPC on drive 0 and steamOS or ubuntu14.04+steam on drive 1.

(I will report back if somehow I get the side by side to work.)

Again balky, I appreciate your input and help.