Discussion in 'Article Discussion' started by Gareth Halfacree, 15 Dec 2016.
Fixes a bandwidth bug, too.
Atmos for home is almost completely unrelated to Atmos for cinemas.
In Cinemas, Atmos works like game audio does: audio sources are positioned in a virtual environment, 'speakers' are placed in that environment in the same palces they are in the cinema (in the same way you would place a pair in the game environment corresponding to ear locations for stereo, or in a ring for 5.1 etc). This emans the spatial mix is always correct for a specific cinema's speaker layout.
For home, Atmos is just a fixed downmix that can be resampled to a limited degree for surround setups, the same way you can already downmix 7.1 to 5.1 (for example). Indeed, Atmos for home is not even a 24.2.10 mix! It's a 7.1 (or even 5.1, or even stereo!) mix, with metadata that provides a weighting to different channels. That metadata is used to mix betwen channels if your speakers happend to be in a different positon than that assumed in the mix (and if you receiver supports that function). Otherwise, a 7.1 Atmos enabled mix with your spekaers setup the same as in the mix, will sound the same as a stock 7.1 mix.
Atmos home is a clever idea to deal with different speaker setups, but it's super misleading to slap the Atmos label on something completely different.
This is pointed out in detail in the article - although your summary misses the bit where the substream is created from the Atmos tracks (which is what makes it Atmos Home Edition rather than something completely different) and supports 24.1.10 channel setups (if anybody has such a thing.)
The Substream is created from the 'Atmos tracks', but that is no more a feature than the substream being created from the original sound mix (which will also utilise spatial positioning and filtering). It would be like calling the on-disc mix "DA-88 Home".
The '24.1.20' channel limit is pretty much arbitrary, the limit on effective fidelity is the actual encoded mix to which the metadata stream is attached, which will in general be 7.1. Because Atmos Home is a metedata stream for TrueHD or DD+, it will have the same encoded channel limits as those formats: 14 channels for TrueHD, or 13 for DD+ (but if you want to remain compliant for BD that is limited to 7.1, so you'd need to 'waste' 8 channels on a compliant mix leaving you with 6 for extra channels). There is no way to encode 24+10+1FLE discreet channels onto a BD disc and have it be BD format compliant (i.e. if you did so, you couldn't call it a Blue Ray Disc, could not sue that name or logo in marketing or packaging, and it would not play in a domestic BD player).
Atmos Home is a a 5.1 or 7.1 track with a metadata track that slightly improves the existing logic AV receivers use in interpolating a 'normal' 5.1 or 7.1 track for a setup with more speaker channels.
I'm seeing 7.1.2...
Can you tell I'm procrastinating?
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