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.