I've mentioned this in another thread, but I think I should also mentin it here too. The soundtrack on both the Blu-ray and the UHD release of Midway are Atmos. Both soundtracks are the one and the same soundtrack and not different. The Blu-ray soundtrack is the same TrueHD/Atmos soundtrack as that on the UHD disc.
Also note that Atmos isn't a seperate soundtrack and is just the same audio data as you'd have gotten via the TRueHD audio being handled by the AV receiver in accordance with what the Atmos metadata is instructing the AV receiver to do relative to your speaker layout.
Dolby Atmos content consists of both sound objects and positional metadata that describes where sounds should be placed and how they should move, along with other data such as the type of object represented, its size, and its volume or intensity. The Dolby Atmos object audio renderer is informed of the speakers available in your system and determines----in real time----which speakers to use to accurately recreate the sound the filmmakers intended. The actual sound onjects are included within the TrueHD or DD+ soundmix and aren't part of a different sound mix.
Dolby Atmos in Dolby TrueHD
Dolby has expanded the Dolby TrueHD format to allow the format to support Dolby Atmos content on Blu-ray and ultra high definition Blu-ray Disc. Prior to Dolby Atmos, Dolby TrueHD provided lossless support for channel-based audio, such as 5.1 and 7.1. Now we have added a fourth substream for Dolby Atmos sound in Dolby TrueHD codec to enable a support for a losslessly encoded object-based sound mix.
Dolby Atmos in Dolby TrueHD is transmitted from a Blu-ray player or Ultra HD Blu-ray player to your AVR via an HDMI connection. If your AVR supports Dolby Atmos, the Dolby TrueHD object-based audio and related metadata will be decoded, processed, scaled, and rendered to your specific speaker configuration. Dolby Atmos audio can be encoded with Dolby TrueHD at multiple sampling rates (including 48 and 96 kHz) and bit depths (16- and 24-bit).
Dolby Atmos enabled receivers will also support legacy Dolby TrueHD bitstreams at multiple sampling rates (including 48, 96, and 192 kHz) and bit depths (16-, 20-, and 24-bit) to provide full backward compatibility with legacy Blu-ray Disc media and Dolby TrueHD music files.
Dolby Atmos in Dolby Digital Plus
Dolby Digital Plus has been updated and features a new decoder capable of processing content encoded for Dolby Atmos. This module uses new bitstream metadata to extract Dolby Atmos object-based audio and outputs this information for further signal processing. The sampling rate for Dolby Atmos content is 48 kHz, the same sample rate as for Dolby Digital Pluscontent.
Both new audio decoders are designed to be fully backward compatible with legacy channel-based Dolby Digital Plus and Dolby TrueHD soundtracks.
THe audio asoect of the audio package is the same irrespective of whether your receiver is Atmos enabled or not. THe only difference is whether the included Atmos metadata is being used to map the audio objects to your speaker layout.
Varioations in levels may in fact be intended in order to better fascilitate and portray the movement of said objects around your room via the speakers you have. As such, I'd not expect a TRueHD soundtrack to sound exactly the same as the same TrueHD audio if and when subject to the AV receiver's interpretation of the Atmos metadata. Even Dolby Surround Upmixing has similar results if applied to non Atmos soundtracks.
Dolby Atmos allows each sound in a movie scene to be represented as a separate audio object. And each of these objects has its own positional metadata, describing precisely where it should originate and how it should move, along with other data.
Filmmakers frequently remix a film to sound its best in home theaters, a process known as creating a near-field mix. Spatial audio coding is a tool available to sound professionals in the near-field mixing process. During playback, filmmakers can monitor exactly how the film will sound when it is encoded to Dolby Digital Plus for streaming or encoded in Dolby TrueHD for Blu-ray and Ultra HD Blu-ray content.
Creating Dolby Atmos soundtracks for home theaters
Initial Dolby Atmos content for home theaters was delivered via Blu-ray Disc and streaming video via over-the-top (OTT) services. For Blu-ray and Ultra HD Blu ray, studios will employ lossless Dolby TrueHD for the primary soundtrack and Dolby Digital Plus for secondary languages. OTT streaming services and cable services are supported by Dolby Digital Plus. In the future, Dolby Atmos content will be delivered via video on demand (VOD) and broadcast (terrestrial and digital) that use multichannel Dolby Digital Plus in their core architecture. Dolby Atmos can also be supported in video game soundtracks and delivered to the AVR for decoding and processing via Dolby MAT.
Production houses that create Dolby Atmos content for home theaters will use a tool called Dolby Media Producer, along with its suite of professional encoding, decoding, and media-related tools.
Before using Dolby Media Producer, though, production houses have the option to perform several preliminary steps, including a near-field remix and remastering of the cinematic master file. In this stage of the process, audio mixers may make small adjustments to the mix to ensure that it sounds as they intended in Dolby Atmos enabled home theaters.