The Dolby Atmos signal is lossy Atmos/DD+. The Apple TV 4K converts the signal to LPCM with Atmos metadata intact(Dolby MAT) and then sends it out. This uses more bandwidth and different devices will recognize and display it as Dolby TrueHD 10 channels or even as 9CH Dolby MAT 192kHz.
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Apple TV 4K sound quality
- Thread starter HairyEars
- Start date
Do you mean that there are no streaming sources that are lossless Dolby ATMOS (i.e., Dolby TrueHD + the ATMOS bits)? Or do you mean that there is no such thing as a "Dolby TrueHD ATMOS"?
Do you have any more information on the specific devices and how they interpret the stream? I am interested knowing a few that detect the stream correctly.
Thanks.
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There are no streaming services supplying lossless Atmos it is all either EAC3+JOC or AC4-IMS.
The Apple Music UI is horribly confusing it means it can supply either lossy Atmos OR lossless stereo.
The only thing the True HD lossless version of Atmos is used for is Blu-ray and UHD Blu-ray.
The peak bitrate for TrueHD Atmos is around 18Mbit/s which is nearly as much as video streaming services use for an entire lossy UHD video and audio stream. The economics just don't work for doing it for audio only.
All devices supporting Dolby Atmos will receive the signal from services correctly. How various devices deliver that signal varies.
Those using disc players know that a “Bitstream” setting gets the job done by simply sending the audio signal to the AVP/AVR for decoding and processing of it.
There are streamers such as the Apple TV 4K 3rd Gen and Amazon Fire Cube 3rd Gen that do not support bitstream. Rather, when audio is set to “Best Available,” these devices will re encode the signal to LPCM for output and can retain Atmos metadata for delivery when doing so.
The bandwidth needed to deliver signals using those devices and settings is increased and many don’t realize that connecting them directly to TVs that only support ARC will result in less than optimal signal output to the receiving end.
While the Amazon Fire Cube does have a Dolby Digital Plus output option that supports Atmos/DD+ and will work over ARC, the Apple TV 4K does not have this option but only a DD 5.1 option that works over ARC. The “Best Available” setting is the only one that will support Dolby Atmos.
What happens if the device downstream of the Apple TV 4K doesn’t support Atmos? Like say a miniDSP HTx. Does it just act like normal 7.1 or does the lack of atmos meta data decoding cause issues?
Michael
It will decode the DD+ bits to 7.1 LPCM and leave the Amos metadata out. It should be a functional 7.1 stream.
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I should have qualified there are no audio streaming services.
The cost of entry for Kaleidescape is at least £5000 probably much more the word 'many' cannot be applied to something costing that much.
It's a bit pedantic but it's not a streaming service the data is downloaded locally before it is played and can only be played on the Kaleidescape devices. This dramatically reduces the back end costs for the CDN
It's primarily a video service it doesn't carry stand alone music.
AppleTV can transport TrueHD Atmos to an AVR (or equivalent) just fine using Infuse.
It can't Infuse can decode TrueHD to PCM 7.1 and it can bitstream EAC3+JOC.
Apple TV doesn't provide the ability to bitstream TrueHD inside MAT or to decode to and transmit MAT2.
Help get (more) Dolby Atmos on Apple TV
With tvOS 17 being announced, I have a feeling you guys will be digging into the CoreAudio and AVFoundation changes to check if audio passthrough changes made it in?
community.firecore.com
Is the epic fire core thread that has been going on for years about this.
Audio Options (tvOS)
Overview Infuse for Apple TV supports up to 7.1 channels of 24-bit 48KHz audio in a wide variety of audio codec formats. Audio Output Settings Audio settings on the Apple TV can be adjusted through...
Specifically says Atmos is only supported for EAC3 and links to the epic thread.
The lack of support for DTHD and DTS are what have kept me from moving on to a new Apple TV 4K and I’m still using a 1st gen model. Getting certain signals out of certain Apple devices is difficult, if not entirely impossible compared to outputting certain signals using other devices.
All good here.
By "less than optimal", are you referring to ARC limited bandwidth for lossless surround audio streams vs eARC which can?
I am a bit confused by the comments regarding DD+ and how different devices interpret the stream differently, so below is a specific example to use as a reference.
The streaming device is an Apple TV 4K (2nd Gen)
Connections and devices are:
ISP (comcast) -> cable modem (bridge mode) to router -> Apple TV -> TV's HDMI eARC -> passthrough -> HDMI eARC to the Sennheiser AMBEO Max soundbar.
The AV cables are all HDMI 2.1 or better for eARC
Network is 1.0 Gbps to the router and Wi-Fi 6 to the Apple TV ~@250+ Mbps (or 900+ Mbps over ethernet).
Apple TV settings
1) Audio Output = "Auto, Atmos Available"
2) Audio Return Channel = eARC
3) Audio format is "Dolby Atmos."
Apple Music App Settings (on the Apple TV)
1) Audio = Dolby Atmos
2) Audio Quality = Lossless (ALAC up to 24-bit/48 kHz)
Sennheiser SB01 relevant settings,
1) dynamic range compression is off, i.e., full dynamics
2) "Dolby Virtualizer" is turned on which allows Dolby audio content to be played back unchanged
Theoretically, this system should easily handle the lossless Apple Spatial Music (24-bit/48kHz) as lossless and the soundbar sees an Apple Music stream as "Dolby TrueHD Atmos", i.e., not lossy., am I missing something? (I've contacted Sennheiser about the accuracy of their app and will let you know the answer).
I thanks.EDIT: My objective is two-fold, to clear up the confusion around Atmos streaming and to understand if one can generalize streaming lossless Dolby Atmos music to streaming Dolby TrueHD Atmos AV content; specifically, when streamed can today's hardware and software properly handle Dolby TrueHD Atmos 4k movies (economics aside)?
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Apple’s “Spatial Audio” tracks are lossy Atmos/DD+ based. Think of the Apple TV 4K as a gift wrapper. It puts the lossy DD+ signal in a big LPCM box and wraps it in an Atmos metadata bow.
Devices that bitstream Atmos from services will display as Atmos/DD+ on the receiving end while those that output the signal as LPCM will display Atmos or Atmos/PCM on the receiving end.
It seems some devices confuse the LPCM delivery of Atmos with TrueHD. I do have one receiver that trips over it for a bit and displays Atmos/DTHD for a moment before figuring it out and displaying Atmos/PCM.
The Apple TV 4K outputs everything as 24/48 by default. This includes the 16/44.1 lossless tracks from Apple Music. It does not support the hi-res tracks from Apple Music that can be output at up to 24/192 on other devices.
Devices that bitstream Atmos from services will display as Atmos/DD+ on the receiving end while those that output the signal as LPCM will display Atmos or Atmos/PCM on the receiving end.
It seems some devices confuse the LPCM delivery of Atmos with TrueHD. I do have one receiver that trips over it for a bit and displays Atmos/DTHD for a moment before figuring it out and displaying Atmos/PCM.
The Apple TV 4K outputs everything as 24/48 by default. This includes the 16/44.1 lossless tracks from Apple Music. It does not support the hi-res tracks from Apple Music that can be output at up to 24/192 on other devices.
Well yes, that’s what I meant, thanks far clarifying.
I’m pretty sure I played some TrueHD with Atmos through Infuse and it worked. I’ll double check next time.
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This is the (last) confusing part. Assuming Apple Music does deliver lossless audio (with or w/out Atmos) as they advertise, how can it be based on lossy audio sources? Do they transcode the lossy audio to lossless audio?
EDIT: I misread @Tre2023 : So, Apple TV 4K is the weak link in the delivery of hi-res (>48kHz) lossless audio.
That makes sense and explains why my Soundbar is likely misrepresenting what the data actually is. ATV's LPCM is enters and exits the TV unchanged. (bitstream in and pass through out)
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Lossless is stereo only. Multichannel versions of the same tracks will be lossy.
I’d say, worry about it after you proved that you can hear the difference. Apple TV resampling is audibly transparent.
As for lossy vs lossless, Apple thinks it’s silly anyway:
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Not my agenda, please reread my objective. Psychoacoustics and/or the ability to detect the difference is not the issue.
The issue is technical.
And they are likely right for many if not most of their subscribers.
Yes, one that Apple thinks is currently not worth the effort of fixing. Maybe with another hardware iteration… fact remains that this is primarily a streaming video device, and for that the current feature set is perfectly fine.
It is very sad that there isn't a single streaming device that offers all of the following:
4k HDR
Dolby Vision
Bitstream Atmos
Video frame rate switching
Responsive, attractive UI
All UK TV catchup (iPlayer, Channel 4)
Please tell me if I'm wrong...
Nvidia Shield TV Pro: No 4k for iPlayer
Apple TV 4k: No bitstream Atmos
LG OLED: Not responsive, no AVR menus
They all seem to have some deal breaking problem. We really need a new generation of streaming devices that actually work properly.
Even if one is prepared to throw money at this problem and build a powerful Windows PC just for TV streaming - are all apps 4k and Atmos compatible?
4k HDR
Dolby Vision
Bitstream Atmos
Video frame rate switching
Responsive, attractive UI
All UK TV catchup (iPlayer, Channel 4)
Please tell me if I'm wrong...
They all seem to have some deal breaking problem. We really need a new generation of streaming devices that actually work properly.
Even if one is prepared to throw money at this problem and build a powerful Windows PC just for TV streaming - are all apps 4k and Atmos compatible?
