[mythtv-users] Can mythtv (or mplayer/xine through mythtv) upmix 5.1 sound in 6.1 or 7.1?

Marc MERLIN marc_mtv at merlins.org
Sat Oct 5 05:35:29 UTC 2013


Sorry for the slight delay in the answer, the unwanted list forced reply to
messed with my sorting filters.

On Wed, Oct 02, 2013 at 11:24:52AM +1000, Jean-Yves Avenard wrote:
> > If my input is DTS 7.1 (I have a very small sample on a test DVD), then my rear
> > speaker works and gives me "behind me" sounds. But most sources I have are 5.1
> > and I just never got sound behind me on the 6th speaker.
> > Turns out, my $1500 (at the time) Denon 3808 receiver cannot upmix 5.1
> > into 6.1 or 7.1.
> >
> > Can mythtv or mplayer piped into mythtv do this in software?
> > Or maybe even some fancy alsa setup?
> 
> with alsa software yes, provided you're willing to drop all digital passthrough.

Which means I'm wasting CPU power to do sound, but I'm ok with that.
Would you happen to have a link?

I tried some alsa configs and didn't have much luck with them. I'll try this
one next:
http://www.3d-zone.org/blog/2011/07/alsa-asound-conf-7-1-upmix-debian-lenny/

> myth only provide up to 5.1 upmixing.

Thansk for confirming.

> There's no such thing as DTS 7.1; the maximum is with DTS ES and 6.1
> .. If your amp is configured as 7.1 and you feed it DTS ES 6.1; then
> the spec state that the two real channels should play the same mono
> channel.

Actualy it's configured as 6.1 in my house since that's the exact number of
speakers I have, but point taken.

> Usually, most receiver will have some DSP mode that would do it

Newer ones than mine from 2008.

> so if it's 5.1, then that's the way it is...
> 
> Also, the rear channel shouldn't be heard as such, it should only be
> "felt" , it provide an ambiance, and atmosphere...
> 
> IMHO, I would change your speaker location slightly if you desperate
> to "hear" the surround info

My room does not allow for this, hence my 6th speaker behind me while 4 and
5 are on the side slightly in front.
It won't be perfect, but if the 6th speaker turned on from time to time on
5.1 sources, that would be cool :)

On Tue, Oct 01, 2013 at 08:32:24PM -0400, Eric Sharkey wrote:
> How are you feeding the audio signal into your receiver?  As analog
> 2-channel stereo or a digital multichannel signal?
 
Digital. Otherwise 5.1 wouldn't work right either :)

> > DTS Neo:X can take stereo, 5.1, 6.1, or 7.1 source material and output up to
> > 11.1 channels including front height and width channels.
> 
> So says the DTS marketing department...
> 
> If you're looking for satisfying surround sound, I'd steer away from
> matrix encoded solutions.

So you're saying that upmixing 5.1 to 6.1 or 7.1 in hardware sucks?

On Wed, Oct 02, 2013 at 11:17:11AM +1000, Jean-Yves Avenard wrote:
> for this to happen, the channels must have been matrixed in the
> original material... otherwise no "upmixing" will occur. It's no
> upmixing either, just separating the channels that have already been
> encoded there

So, here's what I was thinking, tell me if I'm crazy: I have 5.1 input.
If there is sound that is both in speakers 4 and 5, it could be moved to
speaker 6, giving me the 'sound is in the back'
Is that a pipedream?

http://www.avsforum.com/t/1384892/is-dts-neo-x-that-good gives some info,
but it's complicated.

On Tue, Oct 01, 2013 at 09:40:44PM -0400, Eric Sharkey wrote:
> The question is whether a new mid-low end 5.1/7.2/whatever native
> receiver will sound better than this older Denon unit with software
> mixing.  Quite possibly.

So, the algorithm is complicated, needs an expensive DSP and alsa won't do
the job, even on a fast intel CPU?

But back to the point, my 3808 does everything to my needs, so I won't
throw it away just over that.
If I can't upmix 5.1 into 6.1 in software, so be it, but somehow I was
hoping that either mythtv or alsa could do it.

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/  


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