E-AC-3 JOC, AC-4IMS Dolby Atmos Loudness Testing
E-AC-3 JOC, AC-4IMS & AAC files played and compared from Samsung Galaxy (headphone output) with Dolby Atmos enabled and disabled. Same tracks played from Tidal (AC-4IMS & AAC) with Dolby Atmos enabled and disabled. Current RMS value highlights loudness difference with and without Dolby Atmos enabled (even for the Tidal 'High' Stereo AAC playback) although you should hear the 2-3db of loudness gain applied by Dolby Atmos feature on the phone. Interestingly the physical files of the same tracks are overall slightly louder than their streamed version. This I assume is because the Android Tidal app has built-in normalisation to -14 LUFS, YT Music player app doesn't it is the raw playback.
I assume for the physical playback of the E-AC-3 JOC (DD+JOC) the phone is folding the 5.1 to stereo when Dolby Atmos is off and when on, it's processing the JOC to full Dolby Atmos for Headphones playback. Either way, it's louder with Dolby Atmos enabled.
Also of interest is the E-AC-3 JOC is a 5.1 based format and the loudness target of Dolby Atmos is -18LUFS which is measured using the 5.1 fold down, yet it would seem by enabling Dolby Atmos the 5.1 playback to probably being boosted to more like -16/-15LUFS perhaps?