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Max number of Atmos objects on on UHD bluray versus OTT

 Hello,


I'd like to find some online ressource as to why the apparent maximum number of Atmos object is limited to 16 on UHD bluray.


Is a limitation of the Dolby TrueHD codec?

or a limitation from the Dolby software?


I was looking for the same information on OTT deliveries and I found out that the "limitation" was due to DD+ codec specifications. This was documented on the DD+ Version 1.4 release note:

- Update Dolby Atmos signals from 12 objects to 16 objects.

-> Link


Thank you!


It's a poor use of the same term for two different processes. 


Dolby Atmos content creation can make use of 128 channels of which a maximum of 118 can be used in a particular master file. These are then simplified into what are now referred to as Elements in the codecs. This is what Spatial Coding Emulation is presenting in the preferences.


It's part of the process to get information from 128 channels onto a BluRay or streaming effectively. The emulation is in place for creatives to understand and test/monitor how their mixes are going to transfer into consumer playback devices.


Hope that helps 

Hi,


I think you lost me. are you saying that there is no 16-object limitation on dolby TrueHD?

I'm trying to understand why consumer blurays don't offer more than 16 objects.


In the codec, there is a lot of magic to package all the relevant information into those elements. All 118 objects in content creation can be used, the internals of the codecs take care of the rest. 


128 channels for creation -> 16 elements for spatial coding


It's all about how the data needs to be encoded and then decoded by the consumer device. 


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ok, so there is no limitation, the 16 elements is already the max value?

correct.


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