Dolby Atmos and REW

[SeanP]

ok I got the hdmi working but is there away of testing the 0.0.4 over head channels in REW short of switching the overheads output on the preamp to the surround inputs on the amp?

 

[Matthew J Poes]

I don't believe so. REW is sending a signal to each discrete via PCM, but there is no way to send a signal to the effect channels through PCM. You would have to encode the test tones into ATMOS and then send the signals via HDMI to an ATMOS decoder. You will have to switch inputs I'm afraid. This shouldn't be an overly important thing to measure so I wouldn't worry too much about it. Maybe go through the effort once and then don't worry so much.

 

[SeanP]

Thanks

 

[TheSound]

I don't believe so. REW is sending a signal to each discrete via PCM, but there is no way to send a signal to the effect channels through PCM. You would have to encode the test tones into ATMOS and then send the signals via HDMI to an ATMOS decoder. You will have to switch inputs I'm afraid. This shouldn't be an overly important thing to measure so I wouldn't worry too much about it. Maybe go through the effort once and then don't worry so much.

Hi Matthew,

i am struggling a bit on the the same item... If i switch inputs, the measurement in REW will show a frequency curve, that is influenced by the audyssey or dirac AVR measurement set filters (in case its the case, that this will be used in normal operation).

E.G., if i cannot reach with a 5.1 soundcard the surround back right and plug this on the surround right, i will measure the SBR with the audyssey filter for the SR. And i do not know, how big the influence is. With a 7.1 soundcard it should be solved, but for all ceiling speakers it cant be solved. Are there any studies that show, that the effect from the audyssey (e.g.) filters is neglectable?

rgds, Holger

 

[Matthew J Poes]

Hi Matthew,

i am struggling a bit on the the same item... If i switch inputs, the measurement in REW will show a frequency curve, that is influenced by the audyssey or dirac AVR measurement set filters (in case its the case, that this will be used in normal operation).

E.G., if i cannot reach with a 5.1 soundcard the surround back right and plug this on the surround right, i will measure the SBR with the audyssey filter for the SR. And i do not know, how big the influence is. With a 7.1 soundcard it should be solved, but for all ceiling speakers it cant be solved. Are there any studies that show, that the effect from the audyssey (e.g.) filters is neglectable?

rgds, Holger

Are you referring to Audyssey’s upmixer or eq. If the upmixer, then I agree this is not a good way to attempt to measure. It is highly unlikely you will get a discrete measurement of those speakers. If you are referring to the eq, that is on all channels. It’s always impacting your measurements if you do not turn it off.

I am able to measure 8 channels using REW, so I can measure all surround channels.

As for ATMOS, I do not believe it is currently possible to measure the atmos speakers through the atmos channels of the processor without a special test disc, which does not exist. I have looked into authoring it and it’s very expensive. The only atmos mixing software in existence costs quite a bit.

For closed loop systems this is a problem, but for discrete component systems, you can simply temporarily rewire the atmos speakers to another channel and measure in that way. It’s perfectly accurate.

 

[TheSound]

Hi Matt,

thanks for your response... I am talking about the audyssey room measurement.

I use it on my Marantz SR7010 because i take a lot benefit of the dynamic eq and on some sources also of the dynamic volume (e.g. aTV or youtube) and using it optimises by a filter after room measurement the frequency curve of the different speakers (not beeing transparent at all). But if you use audyssey it is as it is. So without enableing audyssey rewiring on the rew measurings is of course fine.

But after enabling audyssey you would get something different. And measuring with enabled audyssey you get "foreign" filters on the frequency curve and a different situation as measured after wiring back.

The question is just: how big is the failure, especially on ceiling speakers

 

[Matthew J Poes]

Hi Matt,

thanks for your response... I am talking about the audyssey room measurement.

I use it on my Marantz SR7010 because i take a lot benefit of the dynamic eq and on some sources also of the dynamic volume (e.g. aTV or youtube) and using it optimises by a filter after room measurement the frequency curve of the different speakers (not beeing transparent at all). But if you use audyssey it is as it is. So without enableing audyssey rewiring on the rew measurings is of course fine.

But after enabling audyssey you would get something different. And measuring with enabled audyssey you get "foreign" filters on the frequency curve and a different situation as measured after wiring back.

The question is just: how big is the failure, especially on ceiling speakers

No easy way of knowing. You really don’t want to measure through dynamic eq modes. They change the eq based on the level of the content. The test is very artificial. That should be judged based on sound alone. Do you like it?

As for measuring the eq filters of the atmos channels with Audyssey enabled, unless I’ve missed something big, you can’t measure that right now. There is not a way to send a test tone to those signals through something like REW.

@John Mulcahy can confirm, but it is my understanding that no software can send a signal with the meta-data to go to an atmos channel without purchasing a license through Dolby. In addition, my understanding of how ATMOS works would make it hard to do. For a contract I have with a manufacturer I actually looked into this. I looked at having a custom test disc authored with specific test tones and sweeps. The company I talked to specializes in ATMOS and DYS:X authoring and has the software needed. They told me it is not possible to send discrete test tones to specific atmos speakers. You send it to a geometric position in hemispherical space. The processor then decides which set of speakers get the sound with what level and eq. That makes measuring through ATMOS nearly impossible.

A better solution might be to see if the receiver has built in pink noise that can be sent to discrete atmos channels and using the RTA mode. This may or may not work depending on the kind of pink noise built in and how it’s piped through the processing chain. They might bypass the Audyssey eq filters for example. They may also use a weighted pink noise that gives an artificial response shape. I wouldn’t know without measuring myself.

 

[serko70]

I was quite satisfied with Audyssey calibration for years but the more I understand and utilize REW the less satisfied I have become with MultEQ-32. So now I double check even the distances and levels for each speaker with REW after calibration. And to my disappointment there is a lot that's wrong. So I re-calibrate all the levels and distances and use the Audyssey app to limit equalization ranges beyond which REW measures to be not ideal. The results have been impressive so far. It is easy to do this with ASIO4ALL (or flexasio if you will use only one PC) and an HDMI connection to a receiver for the ear level channels (7.1) but I could not find any way to measure the ceiling speakers. There is an app in WIndows store which can send sound to 2 ceiling speakers together but it is useless. Now I will literally unplug all surround speaker connections and replace them with atmos connections behind the receiver and adjust their levels and distances as I would do with the 7.1 set up. Then put everything back together. Let me know if anyone of you could come up with a more refined solution.

 

[TheSound]

Hi, i just recently did an enclosed measurement study after installing a curtain. An its definetly like that. The leveling of audyssey and the determination of the distances for the delays are quite unprezise, especially on my rear speakers. Front was quite ok. But i admit, this may depend on the room situation and speaker types used.

levels, delays of my surround and back surround bi pol speakers benefitted dramatically from Rew finetuning. And the determined Crossover frequencys for the fronts and the chosen sub delay was really bad.

i would with my know how from now recommend to finetune the systems with REW on 8 channels and balance the height speaker levels by rew and the umik micro e.g. based on the receiver test tones.

I really hope, that something progresses on the measuring system side like audyssey or dirac to close that gap

 

[Aleks]

Well, we can download from Dolby demo page frogs sounds and dogs barks, but we can not download calibrated pink noise or frequency sweeps for Atmos speakers.
Dolby says "If you’re calibrating a new Dolby Atmos® setup, you actually don't need a Dolby Atmos demo disc. Instead, we recommend using the calibration tools built into the AVR."

The AVR calibration tool did not detect a broken tweeter on the new Atmos speaker. REW did. The calibration tools built into the AVR did not recommend defining the speakers as large because I had a -40 dB hole at 70 Hz for small speakers. REW did.

Calibration tools built into the AVR are not as accurate as REW. If not in absolute measurements, it would be better to set up Atmos speakers with relative measurements if we had a program or calibration samples. Thanks to the REW program I have a flatter frequency response, equal SPL levels, overall better sound experience.

Tell to Dolby what we think on the Dolby support page. In fact, Dolby does not want to give end-users of its products the tools to optimize their system for the home environment.

 

[thothsong]

Dolby has Atmos pink noise test tones for download:
https://download.dolby.com/us/en/test-tones/dolby-test-tones_9_1_6.mp4
https://download.dolby.com/us/en/test-tones/dolby-test-tones_7_1_4.mp4

Studio Six Digital has a Surround Generator app for Apple TV devices that contains Atmos 9.1.6 frequency sweeps, as well as pink noise.

 

[Aleks]

Thank you, Thothsong. Your URLs led me to the website web.archive.-org/-web/-20180121102416/-https-:/-/www.dolby.com/-us/en/-guide/test-tones.html (remove character - )
I didn’t find these samples on Dolby’s official website. Do you know the official URL?

 

[thothsong]

Both URLs work fine for me as-is in Chrome, I just checked them again. The URL text is as it visually appears in my post.

 

[craig john]

@John Mulcahy

Sorry to revive an old thread, but this seems a pertinent topic. Getting REW to be able to send test tones to the overhead or height speakers would be a huge benefit for those of us using them. However, several of the previous replies stating the issues/problems with making this happen seem confusing or just plain wrong:

I am able to measure 8 channels using REW, so I can measure all surround channels.

As for ATMOS, I do not believe it is currently possible to measure the atmos speakers through the atmos channels of the processor without a special test disc, which does not exist. I have looked into authoring it and it’s very expensive. The only atmos mixing software in existence costs quite a bit.

and

As for measuring the eq filters of the atmos channels with Audyssey enabled, unless I’ve missed something big, you can’t measure that right now. There is not a way to send a test tone to those signals through something like REW.

@John Mulcahy can confirm, but it is my understanding that no software can send a signal with the meta-data to go to an atmos channel without purchasing a license through Dolby. In addition, my understanding of how ATMOS works would make it hard to do. For a contract I have with a manufacturer I actually looked into this. I looked at having a custom test disc authored with specific test tones and sweeps. The company I talked to specializes in ATMOS and DYS:X authoring and has the software needed. They told me it is not possible to send discrete test tones to specific atmos speakers. You send it to a geometric position in hemispherical space. The processor then decides which set of speakers get the sound with what level and eq. That makes measuring through ATMOS nearly impossible.

A better solution might be to see if the receiver has built in pink noise that can be sent to discrete atmos channels and using the RTA mode. This may or may not work depending on the kind of pink noise built in and how it’s piped through the processing chain. They might bypass the Audyssey eq filters for example. They may also use a weighted pink noise that gives an artificial response shape. I wouldn’t know without measuring myself.

Both of these explanations assume that the overhead or height channels are "Atmos" channels and require the Atmos decoder to receive a signal. What if the user is actually using them as DTS:X speakers or Auro 3D speakers? Why would one want the Atmos decoder involved in the signal processing chain for those signals? Is there no way to bypass or circumvent the Atmos decoder and address the overhead or height speakers directly as receiver channels, not Atmos channels? Only the Atmos "meta-data" needs to be dealt with separately. The Top Front Right receiver output shouldn't need the meta-data to adress that receiver channel.

Further, do systems like Audyssey, Dirac, ARC, etc. engage the Atmos decoder to send signals to the overhead/height speakers during their calibrations and EQ's? That would seem counter-intuitive since their settings apply universally for all codecs, not just Atmos. If Audyssey/Dirac/ARC can address the overhead/heights directly as "channels", why can't REW do it? They shouldn't need to buy an Atmos license just to be able to address a channel in a receiver.

Any clarification provided would be appreciated. Also, any updates on getting test tones that can address the overhead/height channels would be greatly appreciated. Thank you.

Craig

 

[John Mulcahy]

The additional channels are derived from decoding the content by the relevant decoder. Internal EQ solutions can access receiver output channels directly, but there is no access for an external device unless it can generate suitably encoded content.

 

[craig john]

Thanks for the reply and explanation.

Craig

 

[Matthew J Poes]

@John Mulcahy

Sorry to revive an old thread, but this seems a pertinent topic. Getting REW to be able to send test tones to the overhead or height speakers would be a huge benefit for those of us using them. However, several of the previous replies stating the issues/problems with making this happen seem confusing or just plain wrong:

and

Both of these explanations assume that the overhead or height channels are "Atmos" channels and require the Atmos decoder to receive a signal. What if the user is actually using them as DTS:X speakers or Auro 3D speakers? Why would one want the Atmos decoder involved in the signal processing chain for those signals? Is there no way to bypass or circumvent the Atmos decoder and address the overhead or height speakers directly as receiver channels, not Atmos channels? Only the Atmos "meta-data" needs to be dealt with separately. The Top Front Right receiver output shouldn't need the meta-data to adress that receiver channel.

Further, do systems like Audyssey, Dirac, ARC, etc. engage the Atmos decoder to send signals to the overhead/height speakers during their calibrations and EQ's? That would seem counter-intuitive since their settings apply universally for all codecs, not just Atmos. If Audyssey/Dirac/ARC can address the overhead/heights directly as "channels", why can't REW do it? They shouldn't need to buy an Atmos license just to be able to address a channel in a receiver.

Any clarification provided would be appreciated. Also, any updates on getting test tones that can address the overhead/height channels would be greatly appreciated. Thank you.

Craig

John answered this below. What he is saying is that you can't send it to the ceiling speakers directly. The only way to send a sound signal (from an external sound source) to the ceiling speakers is via a decoder. It doesn't matter what decoder you are using, that remains the only way to send sound there. So even if you are doing DTS or something else, then the test signal needs to be encoded such that it can be sent through to the corresponding speaker. That means REW must have an encoder built in. It would be a little silly to build in all of them, since ATMOS is the most widely used, I would assume that would be the one that is chosen, if any. Other companies that have developed test tones for overhead or object based systems have all used ATMOS. If you look at the user statistics, it is by far the most widely used object based format in peoples homes. It costs quite a bit of money to make use of the encoder, even in a free open source product, so they have made a decision that is the best business decision for them.

The only workaround for this are that high end processors like those from Trinnov and Storm let you fully customize the MUX such that you can send a test signal to the left input channel and then send that input signal to any output channel. Someone told me that Anthem now lets you do that too, but for the most part, I haven't come across many other receivers or processors capable of customizing the input to output mapping.

 

[Michael Boeker]

Dolby has 5.1.2, 5.1.4, 7.1.2, 7.1.4, and 9.1.6 Atmos encoded test files with full bandwidth pink noise. I bitstream these from my laptop and use the RTA in REW to take measurements. It only takes a few minutes to get frequency response measurements of all speakers in a system.

 

[Matthew J Poes]

Dolby has 5.1.2, 5.1.4, 7.1.2, 7.1.4, and 9.1.6 Atmos encoded test files with full bandwidth pink noise. I bitstream these from my laptop and use the RTA in REW to take measurements. It only takes a few minutes to get frequency response measurements of all speakers in a system.

That is the approach I've used for some of my testing, but at least for myself and some others doing similar testing, this limits you dramatically to what can be tested.

For example, if I am bench testing a receiver and I need to test all amplifier channels (many of todays receivers use a different and lower grade amplifier in the ATMOS channels) then I can't. I can't send the right kind of signal for power or distortion testing.

If I want to measure the atmos speakers to test time alignment with other speakers, again, I can't. An impulse can't be sent.

So while basic frequency response can be sent using a Dolby ATMOS test disc, for me, it's not a replacement for a lot of the other kinds of testing I need to do.

I also use in-room distortion data to set limiters in some of the bigger and more complex systems. In those systems I can bypass the processor or re-map the channels, but...Again, this is a scenario where it would be nice to just do it via atmos encoded test signals of choice.

In fact, this came up for me, originally, because I was asked to fully characterize something like 30 ATMOS soundbars on the market and submit a report. I was supposed to do CEA-2034 maximum output testing of all channels, including the discrete ATMOS channels that some of them had. But that requires the use of special pure tones and a special bandwidth limited pink noise. I couldn't do it and had to use the Dolby pink noise. Because it isn't bandwidth limited in the same way, it under-stated the maximum output. I did some comparison tests with L-R channels to see the difference and it was about 3-6 dB less output between the full bandwidth and CEA-2034 bandwidth limited pink noise. I was nervous to simply add it on as a correction file in case the bandwidth limiting impacts the ATMOS speakers differently than the L-R speakers (given that the drivers and amplifiers are different for those channels).

I was working, for a bit, with a guy that was planning to release an update to a test disc he had releated previously. It was to be updated with UHD 4k test patterns and HDR test images. He asked me what I would want for sound tests, and I had suggested authoring discrete sine sweeps to all channels up to a 9.1.6 system. I sent him the sine sweep file to use and explained how it would need to be included in the disc to be useful, but I am not sure what ever happened. I think the project was abandoned due to costs.

 

[Michael Boeker]

On my StormAudio processor I don't need to re-map any channels. I can just choose External Signal in its Generator and and play test signals, including from REW, through any channel.

For example, if I am bench testing a receiver and I need to test all amplifier channels (many of todays receivers use a different and lower grade amplifier in the ATMOS channels) then I can't. I can't send the right kind of signal for power or distortion testing.

What receiver doesn't allow a test signal to be sent to all channels? I haven't come across any.

 

[Matthew J Poes]

On my StormAudio processor I don't need to re-map any channels. I can just choose External Signal in its Generator and and play test signals, including from REW, through any channel.


What receiver doesn't allow a test signal to be sent to all channels? I haven't come across any.

I am guessing we are not understanding each other. However, you seem to suggest you have a solution none of the rest of us are aware of. How do you take a sine sweep from REW and route it to a specific ceiling speaker channel? I am unaware of any receiver that allows that. If you know how to do that, please explain. Certainly that wasn't possible with the soundbards, but I couldn't figure out how to do that with a receiver either.

As for the Storm, thats what I meant by remap, same basic idea. I knew it was very easy with Trinnov (The product I work with) and Storm, just not with most others (though again, if you know of some way to do this with all receivers, I am all ears. This has been an ongoing serious challenge for us. I mean, folks at Harman called me to ask me how to do it, so they are unaware as well. They were looking to author their own test disc for some work they were doing.

 

[Michael Boeker]

If you want to do more than frequency response, then in most receivers you can use the amp assign feature to assign the various height/presence channels as Zone2, Zone3, or Bi-Amp. This lets one send test signals directly through those outputs via HDMI input. This works for Denon, Marantz, Arcam, Yamaha, and many others. Once testing is done, one can revert back to the correct output setup for the room. As an example, one can send any REW test signal through all the output channels of a Yamaha RX-A3080

or Denon AVR-X3700H

You can leave the speakers connected to those channels or output to an oscilloscope, etc.

For setting distance, the Dolby Atmos pink noise test signals work just fine for measurements with SMAART's dual channel transfer function measurement and delay finder.

 

[thothsong]

If there's someone with a Mac who has or is willing to buy Logic Pro, it sounds like it should be possible to take an REW-generated sweep file and produce Atmos tracks tied to specific 3D spatial positions, which would allow for 9.x.6 measurements. I have a neighbor who's planning to buy a Mac and Logic Pro for Atmos music production, but no firm timeline.

 

[Michael Boeker]

I forgot to mention that one can also use the Sound Generator App for Apple TV 4K to output many signals via Dolby Atmos.

https://apps.apple.com/us/app/surround-generator/id1254544184

Surround Generator is an audio signal generator for Apple TV that can send test signals to specific speaker channels. The app has Dolby Digital 5.1, 7.1, and Atmos (optional) test signals available in several types.​

​

Use these signals to test, calibrate, and adjust your sound system for the best audio experience possible. To use these, you need a system for analyzing the test signals both in frequency and level. They are designed specifically for the iOS app AudioTools, which has a number of test and measurement modules available.​

​

Formats include 5.1 surround, 7.1 surround, and optionally Atmos 9.1.6 test signals. Apple TV 4k is required for Atmos signal support.​

​

Note: This app does not include any testing capabilities, other than being able to make sure that your speakers are assigned to the correct channels, left, right, center, surround, and height.​

​

The test signals in Surround Generator include:​

​

● Full-Band Pink Noise for Frequency Response Tests​

● Mid-Band Pink Noise for Level Tests​

● Impulse for Time Delay and Room Acoustics Tests​

● Speaker Polarity Test Signal​

● 7-second Impulse Response Sweep Signal​

● 0.5s LARSA Chirp Signal​

Note that you have to have surround sound and Atmos set up in your Apple TV and audio processor or receiver to be able to use this app.​

 

[thothsong]

I forgot to mention that one can also use the Sound Generator App for Apple TV 4K to output many singles via Dolby Atmos.

Yes, but the sweeps aren't compatible with REW.