LUFS/LFKS: Chaos in the World of Audio Streaming. Who is to Blame?

[TLS Guy]

I have just started Atmos audio streaming as the BPO have just started streaming concerts in Atmos.

There are two major issues. The level of the Atmos stream I measure to be about 10db below the two channel stream. Unfortunately just upping the volume is not an ideal solution. The reason is that two channel is the default. This would be fine if you could just leave things well alone for the whole concert. However between works it reverts to the two channel stream and if you don't hit the stop at the end of the work, then the next work starts with a 10db speaker busting increase in level. To get back to the Atmos stream for some odd reason you have to toggle it twice!

Now I have found this is not unique to the BPO and the LG app for the BPO I am using via eARC. Tidal in particular I understand suffers from this level problem.

Here is why the problem occurs.

LUFS and LUKS are virtually the same thing and not to be confused with db, although there is a connection. LUFS are a measure of average loudness over time and take into account the equal loudness curves.

Now this is how Dolby Atmos is affected. Dolby have specified that all Atmos productions be rendered to -18 LUFS. The Dolby renderer and the renderer in Pro Tools do this and I'm sure the one in the recently introduced Cubase version does also.

Now if a producer tries to make the production hotter then -18 LUFS, it has to be rejected by the streaming service.

Below are the LUFS of common streaming services.

So if a stereo stream is -9 LUFS, then the Atmos stream will play 9 db. quieter on average. If it is Apple music, only about 2 db. quieter.

The only solution is to have the App in the device doing the streaming, bring the level up to their 2 channel level. I'm finding some do, and quite a lot don't. There is a lot of complaint about this on the NET.

Dolby say they set the LUFS at -18 for the movie producers, as a lot of the Atmos music is for background. If it is a production that is not a movie, then this sucks.

Have any members streaming Atmos noticed a difference in level between the stereo and Atmos streams?

As I said, I have seen lots of complaints. I had to do a lot of research to understand this problem.

 

[Trebdp83]

I wondered when they were going to add Atmos. Thanks for the information. I will have to check it out. Atmos volume using Tidal is ridiculously low on any device. You really have to crank it. Not so much with Apple Music Atmos. Unfortunately, the LG Apple Music app did not support Atmos the last time I tried it.

 

[TLS Guy]

I wondered when they were going to add Atmos. Thanks for the information. I will have to check it out. Atmos volume using Tidal is ridiculously low on any device. You really have to crank it. Not so much with Apple Music Atmos. Unfortunately, the LG Apple Music app did not support Atmos the last time I tried it.

Yes, tidal must use native LUVS -18 without the app being able to correct it to match their stereo stream in the App. I suspect this is no easy task. Then you have to convince the vendors like ROKU, LG, Samsung, etc. to support it. I really think that Dolby labs need to rethink this. It is not just Hollywood who wants to use Dolby Atmos. The fact is, that Dolby Atmos is the best immersive system. It has widespread industry adoption, and works very well. This hard enforcement of the renderers have to be LUVS -18 is not helpful, and a significant barrier.

I thought that Apple Music supported Atmos. Thanks for setting me straight on that. It really is a pity that this policy is a significant barrier. It is severely aggravated for the classical community, as the dynamic range of a lot of program is colossal. So this really aggravates signal to noise issues. There is no doubt in my mind, that if this is to really catch on for music streaming, then this issue needs to be addresses and fixed pronto.

I don't watch many movies, so have not used much native Atmos. I have mainly used the studio speaker system with the Dolby upmixer, which I think does a tremendous job, if your system is designed correctly and properly calibrated.

I have to say that this forum is the place to hang out if you want the answer to audio's difficult and and enigmatic problems. The other forums mention what we are talking about, but it is not explained. I had to go to the professional literature to understand this issue. I think we have many here who search for what is really driving important issues and conundrums.

 

[Replicant 7]

Thanks for taking the time on researching this Doc. I was streaming You music this past weekend. When switching between music videos I did notice volume drops between some. A few where so bad I'd have to crank up the volume to 15db just to get about 60db in volume. Not in Atmos but still. Someone not knowing without this info may think something is up with their audio gear.

 

[Trebdp83]

Apple Music supports Atmos but the LG TV Apple Music app does not support Atmos. One would need an Apple TV 4K connected to their system for Dolby Atmos via Apple Music.

The BPO(DigitalConcertHall) app on Apple TV 4K and LG TV both look great in 4K. Apple’s app supports hi-res as well as Atmos BUT the Apple TV 4K does not and everything gets played back at 48kHz on the Apple TV 4K. One would need an external DAC connected to an iPhone or Mac to get hi-res from any apps that support it.

The LG TV Apple Music app does show Spatial Audio(Atmos) selections but they are all played back in stereo. The Dolby Atmos, Lossless and Apple Digital Masters labels are are gone from albums/tracks using the LG TV Apple Music app. Tidal Dolby Atmos tracks work on the LG TV Tidal app and the Apple TV 4K Tidal app.

I like the BPO app’s ability to change from Atmos to Stereo within the track. The Dolby Atmos volume is very low compared to the stereo version and similar to the low volume when playing Tidal’s Dolby Atmos tracks. I can see many using their favorite upmixer for the much louder stereo track.

 

[TLS Guy]

Apple Music supports Atmos but the LG TV Apple Music app does not support Atmos. One would need an Apple TV 4K connected to their system for Dolby Atmos via Apple Music.

The BPO(DigitalConcertHall) app on Apple TV 4K and LG TV both look great in 4K. Apple’s app supports hi-res as well as Atmos BUT the Apple TV 4K does not and everything gets played back at 48kHz on the Apple TV 4K. One would need an external DAC connected to an iPhone or Mac to get hi-res from any apps that support it.

The LG TV Apple Music app does show Spatial Audio(Atmos) selections but they are all played back in stereo. The Dolby Atmos, Lossless and Apple Digital Masters labels are are gone from albums/tracks using the LG TV Apple Music app. Tidal Dolby Atmos tracks work on the LG TV Tidal app and the Apple TV 4K Tidal app.

I like the BPO app’s ability to change from Atmos to Stereo within the track. The Dolby Atmos volume is very low compared to the stereo version and similar to the low volume when playing Tidal’s Dolby Atmos tracks. I can see many using their favorite upmixer for the much louder stereo track.

Thanks for that. The biggest problem is that the app reverts to stereo between tracks. That is a huge problem, because of the massive volume discrepancy.
I have not tried using my iPhone with my 4K ultra chrome caster, but it will be the chrome caster that handles the signal direct from the router. The iPhone is just the control device. My reading of the BPO site suggests that this should work. If it does though, I would bet it would have the same issues.

One thing I have learned from this experience is that Dolby Atmos streaming is not ready for prime time, and is at virtual Beta stage development, if that. It needs much further work, and because of the -18 LUFS streaming requirement, I think the ball is in Dolby's court. I would suggest a different protocol for movies and music streaming. I'm not convinced it was wise to put a volume limit on the movies either, as some are musicals in any event. But if there were two distinct protocols a movie producer could choose which he wanted to use. The current set up is chaos, and as I say, not ready for prime time. I must say, I expected better.

 

[Trebdp83]

Yeah, the Dolby Atmos implementation needs work. I also started thinking more about the Hi-Res setting in the BPO app and downloaded it to my iPhone. It also needs work.

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