INTERACT FORUM

Please login or register.

Login with username, password and session length
Advanced search  
Pages: [1]   Go Down

Author Topic: Linked Zones  (Read 2915 times)

THX-UltraII

  • Recent member
  • *
  • Posts: 15
Linked Zones
« on: April 06, 2014, 07:02:53 am »

I m trying to play a movie with linked zones. I get a notification that linked zones are only supported by audio playback. Is there a workaround to play my Blu-Ray movie content (mostly BDMV/CERTIFICATE structure folders) with a linked zone? I need 2 audio devices to play my movies.
Logged

glynor

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 19608
Re: Linked Zones
« Reply #1 on: April 06, 2014, 09:05:05 am »

Not really if they're separate audio devices.

I was able to hack around it for my kitchen setup, but you might not be so lucky.

On my HTPC, I have the following audio outputs:

1. HDMI
2. Onboard Realtek SPDIF Out
3. Junk onboard Realtek analog outs (not used)
4. Some other stuff not relevant or used (speakerphone mics and whatnot)

My receiver has two zones, and I can remote control it via Girder.  My speaker setup in the living room is a 5.1 setup (not full 7.1 or anything).

So, in Media Center, I have three zones.

1. Normal - this uses the HDMI to my receiver and has 5.1 set in DSP > Output Format > Channels.  It is used in the living room.  This uses "Normal Receiver Configuration" which has HDMI to Zone 1 (the Living Room), and SPDIF to Zone 2 (the kitchen).  My receiver is set to use this zone "most of the time" (my remote sets this when powering up, or switching the receiver to HTPC mode).

2. Kitchen - this uses the SPDIF out and has 2 channels (with downmixing) set in DSP > Output Format > Channels.  It is used in the Kitchen, and also uses "Normal Receiver Configuration".

If all I was doing was playing music, that's all I'd need.  You could link the two zones and it works pretty darn well.  But, not at all for video playback, so...

3. Unified - this uses the HDMI out.  This uses a different configuration of the Receiver (so requires a Girder command to activate), where the receiver "thinks" it is in 7.1 mode (it doesn't know the speakers are in a different room).  However, Media Center is set to 5.1 channels (inside 7.1 container) mode in DSP > Output Format > Channels and it has the Parametric EQ set with the following filters:



I should note: I'm sure those PEQ filters are not technically "correct", and I'd be into it if someone showed me how to do it mathematically properly for a full 5.1 downmix to stereo, routed to the RL and RR respectively.  But this works well enough for listening to a show while you wander out to the kitchen for a new beer or to cook dinner.
Logged
"Some cultures are defined by their relationship to cheese."

Visit me on the Interweb Thingie: http://glynor.com/

fitbrit

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 4887
Re: Linked Zones
« Reply #2 on: April 07, 2014, 12:24:20 am »

Shouldn't you be adding the SL and SR to the RL and RR respectively too?
Logged

glynor

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 19608
Re: Linked Zones
« Reply #3 on: April 07, 2014, 07:39:30 am »

Shouldn't you be adding the SL and SR to the RL and RR respectively too?

Yeah, probably.  But:

1. I didn't care very much.
2. Math is hard.
3. Those channels aren't really used for very much in the vast majority of content.
4. I'll never watch something "important" with those speakers enabled.

So, if you can figure out what I should be using, to prevent clipping, but handle the proper "JRSS" to those two rear channels, I'd love to hear about it.  Otherwise, this works well enough for me.
Logged
"Some cultures are defined by their relationship to cheese."

Visit me on the Interweb Thingie: http://glynor.com/

6233638

  • Regular Member
  • Citizen of the Universe
  • *****
  • Posts: 5353
Re: Linked Zones
« Reply #4 on: April 07, 2014, 08:45:37 am »

So, if you can figure out what I should be using, to prevent clipping, but handle the proper "JRSS" to those two rear channels, I'd love to hear about it.  Otherwise, this works well enough for me.

http://yabb.jriver.com/interact/index.php?topic=87945.msg606061#msg606061
Logged

mwillems

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 5233
  • "Linux Merit Badge" Recipient
Re: Linked Zones
« Reply #5 on: April 07, 2014, 09:05:17 am »

Yeah, probably.  But:

1. I didn't care very much.
2. Math is hard.
3. Those channels aren't really used for very much in the vast majority of content.
4. I'll never watch something "important" with those speakers enabled.

So, if you can figure out what I should be using, to prevent clipping, but handle the proper "JRSS" to those two rear channels, I'd love to hear about it.  Otherwise, this works well enough for me.

Two perfectly correlated signals of equal volume sum +6dB, two perfectly uncorrelated signals of equal volume sum +3dB.  Real-world signals are rarely perfectly one way or the other, but tend towards lack of correlation.  As Matt pointed out in the past, any real-world mixing will be a compromise between volume and clipping (i.e. you can downmix in a way that guarantees no clipping, but your volume will be very low). See, e.g.  http://yabb.jriver.com/interact/index.php?topic=79282.msg538644#msg538644.  

My recollection is that JRSS assumes channels are incoherent (which is mostly true, there is some overlap), which risks clipping in some "perfect storm" scenarios.  In the case of moving the center to the L and R, it's a better idea to assume 6dB of gain from that duplication as the signal is (necessarily) perfectly correlated.  I'm not sure that the whole JRSS matrix is public info, but we know that the mono downmix is -1.76 dB for LFE and -11.76 dB for other channels.  But we can reconstruct a usable matrix using the math of audio summing .

For your current setup (if you really don't care about the surround or LFE info on those speakers), you should probably adjust the L and R info down by 1dB during the copy to RL and RR, and then add the center at -7dB.  I think that will be more energy neutral; with your current settings, the center is -3dB from your L and R, even after the 6dB of gain from duplication.  Those settings will be relatively safe, but won't guarantee no clipping.  If you want to guarantee no clipping, use -3.6 dB on the L and R when copying and -9.6dB on the center.

If you want to add in the surrounds, there's a few different theories about how to do that (do you add both channels at different volumes/polarities to both mains, or just the left to the left and right to the right?).  I don't know how JRSS works it out, but you won't go far wrong by adding the SL to the RL and the SR to the RR.  In that scenario, you'd want to copy the L and R data to the RL and RR at -3.6dB, and add the center to both at -9.6dB, and the SL and SR at -3.6dB as well, etc.  If you want to guarantee no clipping, you'll need -8dB on L,R, SL, and SR and -14dB on the center.

If you want to integrate the LFE, you need 4dB of separation between it and the other channels (when it sums +6dB, that will make up the 10dB differential between LFE and other channels), so then you're talking about (theoretically) adding the L,R,SL, and SR channels at -6.8dB, adding the LFE at -2.8dB and the center at -12.8dB.  Based on the mono downmix target above, I think that's probably similar to the amount of headroom that JRSS creates so should be as safe as JRSS in regard to clipping. If you want to guarantee no clipping, you'll need -8.2 on the LFE, -12.2dB on L,R, SL, and SR and -18.8dB on the center [edited for math error]

If anyone has more direct knowledge of JRSS and is willing to chime in, I'd be interested in more info about what JRSS actually does.  this is just what the math suggests.

Check out these calculators if you want to investigate/replicate on your own:
http://www.sengpielaudio.com/calculator-spl.htm  
http://www.sengpielaudio.com/calculator-coherentsources.htm

http://yabb.jriver.com/interact/index.php?topic=87945.msg606061#msg606061

EDIT: Whoops ninja'd, I knew someone had posted something recently.  Looks like that downmix weights the surrounds differently than the other channels, and comes to some different conclusions. 6233638, I'd be interested to hear any thoughts you have about why we came to such different conclusions (or where I went wrong  ;D )
Logged

6233638

  • Regular Member
  • Citizen of the Universe
  • *****
  • Posts: 5353
Re: Linked Zones
« Reply #6 on: April 07, 2014, 09:22:45 am »

Whoops ninja'd, I knew someone had posted something recently.  Looks like that downmix weights the surrounds differently than the other channels, and comes to some different conclusions. 6233638, I'd be interested to hear any thoughts you have about why we came to such different conclusions (or where I went wrong  ;D )
When downmixing to stereo, it's valid to use 0.5, 0.7071, or 1.0 for the surround channels - this should theoretically be indicated by the audio source, but LAV Splitter/Audio does not currently read this information, and I don't think it's used very often anyway.

0.7071 is considered to be the "standard" downmix when that information is not present, which is what I used there.
Logged

mwillems

  • MC Beta Team
  • Citizen of the Universe
  • *****
  • Posts: 5233
  • "Linux Merit Badge" Recipient
Re: Linked Zones
« Reply #7 on: April 07, 2014, 09:26:57 am »

When downmixing to stereo, it's valid to use 0.5, 0.7071, or 1.0 for the surround channels - this should theoretically be indicated by the audio source, but LAV Splitter/Audio does not currently read this information, and I don't think it's used very often anyway.

0.7071 is considered to be the "standard" downmix when that information is not present, which is what I used there.

Got it, other than the surround weighting and the -6 v -3 for the center addition, your numbers look pretty similar to the "no clipping ever" 5.1 downmix numbers I calculated, so those issues are probably what's accounting for the delta.
Logged
Pages: [1]   Go Up