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Author Topic: Linked zones and audio drift  (Read 8320 times)

kiwi

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Linked zones and audio drift
« on: April 18, 2014, 12:58:39 am »

I have two zones that are linked.

1. Emotiva DC-1
2. Emotiva XDA-1

Both via USB connections, directly from a mac mini.  One feeds my kitchen while the other is the living room.

After listening to music for a while, they start to drift apart from each other, with one starting to lead the other by enough that it can sound like an echo.  If I pause and restart, they are in sync, but within half a song or so, they drift.

Is there anything that I have to do to make sure that they stay in sync?

(I'm using all default settings, checked and the delays are the same)
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mwillems

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Re: Linked zones and audio drift
« Reply #1 on: April 18, 2014, 09:35:36 am »

I have two zones that are linked.

1. Emotiva DC-1
2. Emotiva XDA-1

Both via USB connections, directly from a mac mini.  One feeds my kitchen while the other is the living room.

After listening to music for a while, they start to drift apart from each other, with one starting to lead the other by enough that it can sound like an echo.  If I pause and restart, they are in sync, but within half a song or so, they drift.

Is there anything that I have to do to make sure that they stay in sync?

(I'm using all default settings, checked and the delays are the same)

I've had the same experience, and I'm not sure there's anything you can do within JRiver to keep them synced. This thread suggests some third party software that might help:

yabb.jriver.com/interact/index.php?topic=88764.0

[EDIT: maybe not, see below]
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6233638

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Re: Linked zones and audio drift
« Reply #2 on: April 18, 2014, 09:47:12 am »

Airfoil would only help if you are playing to AirPlay receivers, not devices which are directly connected to the server via USB.
 
 
Unfortunately the main issue here is that the clocks are separate on the two devices and they will drift over time.
 
What I'm wondering though, is if it ever drifts apart during the first song, or only if it happens over time as you get say 20+ minutes into a playlist?
 
I wonder if Media Center could offer a way of synchronizing playback at the start of each track (possibly by stopping and then restarting playback to the devices?) though this would break gapless playback.
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mwillems

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Re: Linked zones and audio drift
« Reply #3 on: April 18, 2014, 02:21:12 pm »

Airfoil would only help if you are playing to AirPlay receivers, not devices which are directly connected to the server via USB.
 
 
Unfortunately the main issue here is that the clocks are separate on the two devices and they will drift over time.
 
What I'm wondering though, is if it ever drifts apart during the first song, or only if it happens over time as you get say 20+ minutes into a playlist?
 
I wonder if Media Center could offer a way of synchronizing playback at the start of each track (possibly by stopping and then restarting playback to the devices?) though this would break gapless playback.

When I've used zonelink, Media Center resyncs at the start of each track.  The problem, for me, is that the sync isn't really tight enough even within a single song to avoid echo (especially if the song is longer than five minutes or so).  It starts each track in sync, then drifts apart until the echo appears, and then resyncs at the start of the next track.
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kiwi

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Re: Linked zones and audio drift
« Reply #4 on: April 18, 2014, 03:41:18 pm »

This is unfortunate.  I would not have thought that clocks would be off that much to cause very noticeable echo (almost call and response at times) within a song or two.

It's usually within 5m that I start to notice it.

So does that imply that my only option would be to create a combo device through the midi with a master clock.


I am curious, is this suggesting that the two bitstreams are coming out of MC looking exactly the same and one of the two DACs clocks is so far of from the other that it is getting off by close to a second?  something about that doesn't see right.
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mwillems

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Re: Linked zones and audio drift
« Reply #5 on: April 18, 2014, 04:30:16 pm »

This is unfortunate.  I would not have thought that clocks would be off that much to cause very noticeable echo (almost call and response at times) within a song or two.

It's usually within 5m that I start to notice it.

So does that imply that my only option would be to create a combo device through the midi with a master clock.


I am curious, is this suggesting that the two bitstreams are coming out of MC looking exactly the same and one of the two DACs clocks is so far of from the other that it is getting off by close to a second?  something about that doesn't see right.

You only need about 40 milliseconds of drift to get some echo with music http://en.wikipedia.org/wiki/Precedence_effect#History

I think the clocks and/or audio buffering of USB DACs is the issue.  One way to get perfect sync is to connect two interfaces through wordclock, ADAT, or SPDIF (the latter two of which carry both the clock and the audio information).  Another solution is to use a single multichannel interface.
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kiwi

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Re: Linked zones and audio drift
« Reply #6 on: April 18, 2014, 07:51:11 pm »

I think that I could link them into one Zone/device via Audio MIDI setup and select the Drift Correction option.  But then I couldn't split them apart.  (I can't really do the other options because I don't have options for word clocks or an SPDIF out.)

This is way more than 40ms apart.  It's drifting so far that I can hear a full drum sound from one set of speakers and then the other.

Looks like I need to go back to using iTunes for my multiroom setup, since airplay doesn't seem to have any of the problems.  I had really hoped that linking zones would deal with any drifting issues.  At least in my setup it is pretty much unusable in that way.
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6233638

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Re: Linked zones and audio drift
« Reply #7 on: April 19, 2014, 09:07:23 am »

You only need about 40 milliseconds of drift to get some echo with music http://en.wikipedia.org/wiki/Precedence_effect#History
If I have calculated this correctly, if you are 5m from the speakers it would only take 25ms to cause an audible echo then.
 
This is why I wonder if it actually matters to have properly synchronized multi-room audio at all.
 
Obviously the sync errors would be noticeable if you have all units playing together in the same room - but if they are in separate rooms, surely the distance between yourself and the speakers is going to cause echo effects anyway, and that will change as you move around?
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mwillems

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Re: Linked zones and audio drift
« Reply #8 on: April 19, 2014, 09:58:17 am »

If I have calculated this correctly, if you are 5m from the speakers it would only take 25ms to cause an audible echo then.

I'm not sure I follow that exactly, can you elaborate a little?  The distance between the speakers is the key issue, along with one's positioning in relation to them.  If you were 5m from both speakers you'd still need a minimum of 40ms of drift to get an echo.  It's also important to stress that 40ms is about the lower bound for detecting echo; some people can't perceive them until you get closer to 80 or 100ms.  But 40ms makes a useful target for discussion.

Quote

This is why I wonder if it actually matters to have properly synchronized multi-room audio at all.
 
Obviously the sync errors would be noticeable if you have all units playing together in the same room - but if they are in separate rooms, surely the distance between yourself and the speakers is going to cause echo effects anyway, and that will change as you move around?

It depends on the setup.  For example, my kitchen sound source is about 5m from my living room sound source.  You're right that, even if they were synced flawlessly, there would be still be some drift between them, that's unavoidable due to physics.  But bear with me for a thought experiment.

Imagine a circle that has both of the sound sources on its perimeter.  If I'm outside of the that circle, there would be drift due to distance, but it would be, at most, about 15 ms because 5m is the maximum differential distance that sound will need to travel to reach me.  But if I'm inside that circle, the unavoidable sound travel delay will be highly variable, but always less than 15ms because I will never be more than 5m from either speaker.  

So in my 5m separation case, the maximum unavoidable drift is 15 ms, which is not enough to get an echo.  If there were a hypothetical, magic, perfect zonesync available, I would never experience echo with that setup no matter where I was.

Now let's take a different example: imagine the speakers are 13m apart, and imagine my imaginary circle with both speakers on the perimeter again.  If you're well outside of the circle, the sound from one of the speakers will be delayed by as much as 40ms which means you'd probably perceive an echo.  But you'd also be more than 13m from one of the speakers and SPL loses 6dB for every doubling of distance.  So if you were 1m from one speaker and 14m from the other, the output from the second speaker would be more than 20dB quieter than the first one (assuming no obstructions; with obstructions, obviously much lower).  That's not imperceptible, but it's low enough that it might not be distracting.

On the other hand, if you're inside the imaginary circle, you'd typically have less than 40ms of unavoidable delay.  That means with my hypothetical magical perfect sync device, you probably wouldn't experience echoes when in between the speakers, etc.

Obviously with greater distances, avoiding echo becomes increasingly hopeless, but the echoing sound also becomes increasingly inaudible.  

At a lot of the distances one would experience in a domestic setting, really strong syncing would effectively avoid echo.  As a practical illustration, at the start of a track with zonelink engaged, I don't hear echo in my setup.   And the problems of sync-drift become more pronounced when you have three or four sources playing in a relatively small area.

Sync-drift is most noticeable when sound sources are closer to one another, and those are the exact circumstances where strong sync would be most likely to eliminate echo.  In a small open-plan house, the sync drift/echo can be noticeable if you're moving around (ask me how I know).  In a large house, with good separation between sound sources (e.g. three setups on three different floors with distances in the tens of meters) sync is almost irrelevant because you're very unlikely to be able to hear multiple outputs at once to begin with.
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6233638

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Re: Linked zones and audio drift
« Reply #9 on: April 19, 2014, 10:54:29 am »

I'm not sure I follow that exactly, can you elaborate a little?  The distance between the speakers is the key issue, along with one's positioning in relation to them.  If you were 5m from both speakers you'd still need a minimum of 40ms of drift to get an echo.  It's also important to stress that 40ms is about the lower bound for detecting echo; some people can't perceive them until you get closer to 80 or 100ms.  But 40ms makes a useful target for discussion.
It takes about 15ms for sound to travel 5m.
So if 40ms is required for there to be an audible echo, you would only need 25ms of drift.
13.6m away and you have a 40ms delay due to the distance alone.

...
At a lot of the distances one would experience in a domestic setting, really strong syncing would effectively avoid echo.  As a practical illustration, at the start of a track with zonelink engaged, I don't hear echo in my setup.
...
Sync-drift is most noticeable when sound sources are closer to one another, and those are the exact circumstances where strong sync would be most likely to eliminate echo.  In a small open-plan house, the sync drift/echo can be noticeable if you're moving around (ask me how I know).  In a large house, with good separation between sound sources (e.g. three setups on three different floors with distances in the tens of meters) sync is almost irrelevant because you're very unlikely to be able to hear multiple outputs at once to begin with.
I suppose you are correct.
 
It's things like this which really makes me question whether all this expensive audio equipment is worth it.
Use an expensive DAC in each room, and you are likely to have audio drift out of sync.
Use cheap AirPort Express devices or a system like Sonos, and audio will stay synced.
Ah, but you can't control AirPlay devices properly with Media Center, only the free iTunes program does that. (or the $25 Airfoil app if you only want multi-room playback)
 
Want the best audio performance? Bypass the crossover and use a multichannel AVR to drive your speakers, not an expensive two channel DAC and power amplifiers etc.
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mwillems

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Re: Linked zones and audio drift
« Reply #10 on: April 19, 2014, 12:19:54 pm »

It takes about 15ms for sound to travel 5m.
So if 40ms is required for there to be an audible echo, you would only need 25ms of drift.
13.6m away and you have a 40ms delay due to the distance alone.
I suppose you are correct.
 
It's things like this which really makes me question whether all this expensive audio equipment is worth it.
Use an expensive DAC in each room, and you are likely to have audio drift out of sync.
Use cheap AirPort Express devices or a system like Sonos, and audio will stay synced.
Ah, but you can't control AirPlay devices properly with Media Center, only the free iTunes program does that. (or the $25 Airfoil app if you only want multi-room playback)
 
Want the best audio performance? Bypass the crossover and use a multichannel AVR to drive your speakers, not an expensive two channel DAC and power amplifiers etc.

I think it really depends on what your goals are.  For me it was worth it to invest in one nice setup for critical listening/film watching, but I also wound up building my speakers and power amps, which saved me some money.  I grabbed a moderately expensive multichannel DAC because the poweramp and active crossover approach was fun for me. I got to learn a lot about speaker design, building the amps, etc.  But that kind of project wouldn't be fun for everyone, and I definitely wouldn't have been willing to pay what my system (or an equivalent system) would have cost me if I had had to buy it complete.

The point being, high fidelity and having fun getting there was much more important to me than multi-room sync/whole house audio.  I don't think it's probably worth it for me to have very nice systems in other rooms of the house because I do the majority of my social listening in one spot, and I can do my "anti-social" listening on headphones   :) 

The multi-room sync is more of a novelty for me (something I turn on when I do chores that involve moving around the house).  The sync is a little flaky and distracting, but it's not my primary system usage.  As I mentioned in another thread recently, after I realized that nicer tech wouldn't necessarily make for better sync, my kitchen playback setup reverted to the TV speakers on an old Samsung LCD driven by a nearby laptop (which syncs about as well as anything else). 

So I think it's important to try to keep your use case/desired end state in mind, and buy to those priorities.  Which is much easier said than done: you only learn some of the limitations of certain tech as you go along, the tech is constantly changing/becoming more versatile, and one's needs/goals change over time.  So it's all a moving target.  If you pursue the hobby with vigor, you'll inevitably wind up with extra gear (and sometimes very expensive extra gear).  At those times, Ebay is your friend; I'm always amazed at how much used audio equipment will sell for (especially stuff that was expensive at retail).
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kiwi

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Re: Linked zones and audio drift
« Reply #11 on: April 21, 2014, 12:59:31 am »

It's things like this which really makes me question whether all this expensive audio equipment is worth it.
Use an expensive DAC in each room, and you are likely to have audio drift out of sync.
Use cheap AirPort Express devices or a system like Sonos, and audio will stay synced.
Ah, but you can't control AirPlay devices properly with Media Center, only the free iTunes program does that. (or the $25 Airfoil app if you only want multi-room playback)
 
Want the best audio performance? Bypass the crossover and use a multichannel AVR to drive your speakers, not an expensive two channel DAC and power amplifiers etc.

My house isn't that large, with a rather open plan, the den opens into both the kitchen and living room with large openings and no doors.  It becomes most obvious in this room as the sound levels are pretty much balanced as are the distances.

I'm feeling very much the same way.  I've got nice DACs for both rooms and if I drive the DACs from iTunes in any of the following ways:
  • USB Direct (DC1) + AirPlay (aTV + XDA1)
  • Local Airfoil Speakers (DC1) + AirPlay (aTV + XDA1)
  • AudioMIDI combined device - USB (DC1) + USB (XDA1)
  • USB (DC1) + Optical (XDA1)

I have no perceptible sync issues, zero, zilch. 

As soon as I try to use them as a linked zone, I get sync issues.  And it seems really hard to believe that two reasonable high quality DACs have clocks that drift that far out of sync.  And I'm not talking about 40ms where it's at the edge of something maybe not being right or aligned. This is way off. 

I just wish there was a solution to this, as I really like the JRemote + MC experience... (though having a linked volume control would be awesome.  Adjust each individually, but have the ability to adjust them together.)

I have an OliveOne on order, we will see how that works when it arrives.
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kiwi

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Re: Linked zones and audio drift
« Reply #12 on: April 24, 2014, 11:16:41 pm »

I'm curious does anyone else have this problem with zone drift?
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jmczen

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Re: Linked zones and audio drift
« Reply #13 on: July 21, 2014, 09:45:26 am »

Well am trying to better understand the linked zones feature... Here's the limited testing done as have access to a pair of sonos speakers

1) The 2 Sonos Play 1 speakers are found by MC 19 as dlna device...
2) Link the 2 zones together & then proceed to play...
3) Audio is not in sync... Adjust the timing slider but it's really too much of trial and error and get close but not perfect sync

However since these are Sonos, the better way is to simply group the speakers via Sonos controller... then use jriver to play to the master sonos speaker. Perfect audio sync via sonos & interfaced with jriver.
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kiwi

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Re: Linked zones and audio drift
« Reply #14 on: October 10, 2014, 10:24:14 pm »

@jmczen that's exactly what I experienced.  And when it isn't even networked, it shouldn't have any of those problems.  Has anyone tried this with MC20?
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