Dolby Atmos® FAQ

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Mr. Afternoon

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Question for this beloved forum.
Can a .m4a file contain Dolby Atmos? This is what the file is showing...
View attachment 83259
m4a is simply a container.
The codec here is Dolby Digital +, which can carry Atmos metadata.

It shows up as a 5.1 file because lossy Atmos uses 5.1 beds instead of 7.1 beds, from what I understood.
 
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ar surround

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m4a is simply a container.
The codec here is Dolby Digital +, which can carry Atmos metadata.

It shows up as a 5.1 file because lossy Atmos uses 5.1 beds instead of 7.1 beds, from what I understood.
Perhaps someone with enough tech know-how can answer this question that I posted on the Revolver thread:

What I fail to understand is why 4K video will stream just fine, yet something like lossless Dolby Atmos is considered out of reach. I though that high resolution 4K video signals use much more bandwidth than any kind of audio signal? Ripping a blu-ray with video consumes much more disc space than a straight blu-ray audio; and 4K is even larger. So it makes no sense to me.

Why can't Dolby Atmos be streamed in something like 44.1/24? :unsure: Even CD quality 44.1/16 would be acceptable for Atmos.
 

JediJoker

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What I fail to understand is why 4K video will stream just fine, yet something like lossless Dolby Atmos is considered out of reach.
Streaming video is pretty heavily compressed. All consumer digital video formats use lossy compression—even UHD Blu-ray—but to accommodate streaming, the compression is turned up to 11. The bandwidth used for a 4K stream is a mere fraction of the available bandwidth on UHD Blu-ray. Consider that all versions of HDMI, including v1.0, have been multi-gigabit (up to 48Gbps with v2.1). Meanwhile, even single-gigabit Internet connections remain out-of-reach for the majority of consumers. With that in mind, Netflix's maximum streaming bandwidth is 15.25mbps combined for both video and audio. It's no wonder they serve lossy audio, as they must reserve as much bandwidth as possible for video.

Pure audio streaming, however, is a different matter. Assuming a 2:1 lossless compression ratio, each channel of 16-bit/44.1kHz audio would require 352.8kbps of bandwidth. A 7.1-channel bed would therefore require 2.82mbps of bandwidth. I'm not sure how much bandwidth Atmos metadata requires, but let's make a conservative estimate of 1mbps for a total bandwidth of 3.82mbps. It does stand to reason that this should be possible to serve and stream, especially considering that streaming providers are already serving 24-bit/96kHz lossless stereo, which requires 2.3mbps at a 2:1 compression ratio.
 

humprof

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The first of a series of "Inside the Mix" webinars on immersive audio from the Recording Academy's Producers & Engineers Wing was posted on the P&E Wing's website last month. This one is a "Prelude: Immersive Audio 101," with Brian Gibbs, Darcy Proper, Leslie Ann Jones, Jimmy Douglass, and Michael Piacentini. "All of our panelists have worked prolifically in immersive formats from 5.1 surround sound to Dolby Atmos, Sony 360 Reality Audio and Auro-3D." "The series — which will be available on YouTube in the near future — will cover topics including deliverables and quality control, room configurations and tuning, metadata, and creative solutions."
 
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