Apple Music Lossless Hi-Res Audio Coming Soon

[JonFo]

I have yet to validate that 'lossless' 2-ch music is sent over MAT or plain LPCM.

I validated that it uses MAT 2.0 to send audio at all times, as MAT 2.0 spec indicates it can do: "Dolby TrueHD – 24-bit 192KHz/up to 18 Mbps, or 8 channels of LPCM up to 24 Mbps. "

Using my Symth Realiser A16 Atmos headphone processor (a true geeks tool), we see that Dolby MAT is used for an Atmos track (image = Atmos & stream = Atmos (thd)) and that the inner stream is a Dolby TrueHD container with Atmos content.

When playing back Apple Lossless 2ch material, the A16 shows us that it is indeed still using Dolby MAT to send the streams, as the image is till 'Atmos' (meaning MAT), and now the inner stream is PCM. The 'decode' indicates there are only 2.0.0 channels of PCM.

Unfortunately, it does not show bit depth nor sampling rate of these inner streams. But listening to the tracks over headphones, it seems indistinguishable from the 24/96 tracks from the BluRay of the same album I have.

 

[JonFo]

Since a also have the Theta Casablanc, with HMDI, I could add the AppleTV

So, as I noted above, as long as the audio is containerized, it is immune from any transport issues, and now that I've confirmed even 2ch lossless LPCM audio is containerized (via a MAT 2.0 carrier), then there is zero chance of timing issues being incurred over HDMI.

So an AppleTV 4K can be considered a high-res, accurate audio source device, as long as the content being relayed is of sufficient quality. As a playback device, it is going to be transparent.
Just like any other containerized stream (TrueHD, DTS-HD MA, AC3) from a BluRay player, it will be up to the performance of the processor as to how it sounds.

And, this will rock some boats: Playing losses music sources (Amazon Music HD, Tidal HiFi, Apple Music Lossless), an ATV will deliver a cleaner 'signal' to the processor than playing a CD using a BluRay player connected via HDMI.

 

[amey01]

And, this will rock some boats: Playing losses music sources (Amazon Music HD, Tidal HiFi, Apple Music Lossless), an ATV will deliver a cleaner 'signal' to the processor than playing a CD using a BluRay player connected via HDMI.

It sure will. Don't you know Jon that "you can't apply science to audio"? You know, jitter and all, and jitter and jitter and jitty jitty jitter.

But fear not - it can all be fixed with a "re-clocker".

 

[user 49430]

So, as I noted above, as long as the audio is containerized, it is immune from any transport issues, and now that I've confirmed even 2ch lossless LPCM audio is containerized (via a MAT 2.0 carrier), then there is zero chance of timing issues being incurred over HDMI.

Thanks for sharing this Jon, that is great news indeed.

Sooo, my somewhat long-in-the-tooth Classe SSP-800 is strictly HDMI 1.4 and no Atmos. This is a 2 channel system, so I don't have any use for spatial anyway, but I am VERY interested in feeding the lossless audio streams from the ATV.

Do you happen to know if HDMI1.4 devices accept the MAT2.0 protocol?

 

[JonFo]

Do you happen to know if HDMI1.4 devices accept the MAT2.0 protocol?

Technically, HDMI 1.4 has the bandwidth for it (MAT + PCM), but it's the firmware in the processor that will decide if it will handshake with a source for any given format.

You could ask Classe about that, or on a forum.

Worst case, buy a used ATV 4K (the older model) and try it out.

 

[amey01]

Technically, HDMI 1.4 has the bandwidth for it

A bit OT, but what's the deal with HDMI bandwidth?
Consider this:

I can watch a 4K movie:

• Via Netflix, which uses around 15 mbps on a 50mbps internet connection.
• It can come through a nice, thin ethernet cable (or even through the air if wi-fi)
• It comes out of my computer using a 5 Gb/s USB-C link.
• That USB-C link can do many things – such as power supply, share USB connections, run multiple displays, etc.
  • BUT.......
• In order to get that to my 4K screen at 60Hz, I need a huge, thick, rigid HDMI 2 or 2.1 cable capable of 18 – 48 GB/s !!

So what's wrong with HDMI? Why won't a lowly HDMI-1 cable work in the above example, given it is capable of 5Gb/s – well in excess of what is actually required?

 

[JonFo]

A bit OT, but what's the deal with HDMI bandwidth?

Just reinforcing that even early HDMI specs have plenty of capacity for a MAT carrier handshake. But that MAT handshake is between the source and target firmware implementations, it is not part of the HDMI spec at the lowest levels [edit: It is part of the HDMI spec for 1.3 and newer].

MAT is a clever bit of design on how to leverage the original HDMI audio spec (up to 8 channels of 16/192 PCM) to propagate containerized formats (such as TrueHD). They can aggregate all 8 or just a few (in this example I captured, looks like only 4 'fs') of those 'channels' to have a nice wide data path for a bunch of newer formats to traverse.

So MAT is a carrier spec (more like a codec), and it can transport .thd (TrueHD) streams (which in turn have a ton of substream options), plain LPCM (up to 8 channels), and any number of others, such as DD+.

 

[Robert D]

A bit OT, but what's the deal with HDMI bandwidth?
Consider this:

I can watch a 4K movie:

• Via Netflix, which uses around 15 mbps on a 50mbps internet connection.
• It can come through a nice, thin ethernet cable (or even through the air if wi-fi)
• It comes out of my computer using a 5 Gb/s USB-C link.
• That USB-C link can do many things – such as power supply, share USB connections, run multiple displays, etc.
  • BUT.......
• In order to get that to my 4K screen at 60Hz, I need a huge, thick, rigid HDMI 2 or 2.1 cable capable of 18 – 48 GB/s !!

So what's wrong with HDMI? Why won't a lowly HDMI-1 cable work in the above example, given it is capable of 5Gb/s – well in excess of what is actually required?

I've not looked at 8k certified hdmi cables. Are those even beefier? Funny to think, are there even 8k signals for the home?

 

[Stefan_DR3]

Everyone thinks they want greater than 24/48 but that is what the studio uses to encode Dolby and you can't get better than the original source.

Spatial Audio is just one of the new services being offered by Apple. They also have Hi-Res Lossless and Apple TV fails to deliver that tier.

 

[Stefan_DR3]

I have yet to validate that 'lossless' 2-ch music is sent over MAT or plain LPCM. Either will handle the required bit-depth and sample rates, but they might downsample plain LPCM to 24/48 for purposes of adding UI feedback. But hopefully not if one picks the 'no audio feedback' option in the settings. Off to play with all this.

According to The Computer Audiophile (blog linked earlier) Apple Music can't even stream 16/44 unmolested, so while the container used by Apple TV may be great there is something in their streaming chain that is not bit perfect.

 

[Robert D]

According to The Computer Audiophile (blog linked earlier) Apple Music can't even stream 16/44 unmolested, so while the container used by Apple TV may be great there is something in their streaming chain that is not bit perfect.

How does it compare on paper to Sonos? I'm not knowledgeable. Right now I use Sonos for music and Apple tv for movies.

 

[amey01]

Just reinforcing that even early HDMI specs have plenty of capacity for a MAT carrier handshake. But that MAT handshake is between the source and target firmware implementations, it is not part of the HDMI spec at the lowest levels.

I still don't understand. The source / incoming signal comes over the internet at 15mbps. Why does HDMI need any more than that?

I mean, there is very little in the computer world which can process at 48gbps, so why does HDMI need to be capable of it; and how does the cheap SOC in a TV even handle that data rate?

 

[user 49430]

According to The Computer Audiophile (blog linked earlier) Apple Music can't even stream 16/44 unmolested, so while the container used by Apple TV may be great there is something in their streaming chain that is not bit perfect.

I'm having a lively discussion with The Computer Audiophile about his methodology if you are interested.

https://audiophilestyle.com/ca/bits...ss-r1022/page/5/?tab=comments#comment-1141785

 

[JonFo]

I still don't understand. The source / incoming signal comes over the internet at 15mbps. Why does HDMI need any more than that?

Hi Amey, maybe I should have avoided the word 'bandwidth' and instead used 'capability', as you are correct, there is way more than enough bandwidth on HDMI audio carriers to deal with any form of audio, much less the streaming variety, which is heavily data-reduced.

And I need to correct myself, the HMDI spec does quantify MAT as a supported format since HDMI 1.3.
MAT is actually how Dolby TrueHD is transferred from a Blu-ray player to a processor.

 

[JonFo]

I'm having a lively discussion with The Computer Audiophile about his methodology if you are interested

From an ATV (which is iOS -derived tvOS ) I believe it does auto bit-depth/sampling changes, same as iOS. So a 24/96 track, like from Steven Wilson 'To the Bone' album, sounds just like the same track (in the same sample rates) from the Blu-ray. But none of my playback devices displays the detailed incoming sample rate.

As the author of Lumin stated in that thread, if an MQA track can survive the transport across airplay, then it truly is lossless.

But a lot of that discussion is clouded by cross-posting related to transcoding between devices.

I'd be interested in tests that focused on what pops out the other end of an HDMI link to an ATV. That would be much more definitive in terms of understanding the source material, and how the Music app is propagating the contents.

 

[amey01]

Hi Amey, maybe I should have avoided the word 'bandwidth' and instead used 'capability', as you are correct, there is way more than enough bandwidth on HDMI audio carriers to deal with any form of audio, much less the streaming variety, which is heavily data-reduced.

And I need to correct myself, the HMDI spec does quantify MAT as a supported format since HDMI 1.3.
MAT is actually how Dolby TrueHD is transferred from a Blu-ray player to a processor.

I am still confused! Not just MAT......video too. Why can't I get a 4k/60hz signal on a HDMI 1.4 port (for instance)?

As you said - it has more than enough bandwidth. But ostensibly, it doesn't (because it doesn't work!!) What gives?

 

[ttocs]

I am still confused! Not just MAT......video too. Why can't I get a 4k/60hz signal on a HDMI 1.4 port (for instance)?

HDMI 1.4a or HDMI 1.4b?
At what color depth?
Cripple the color depth and you might get more frames per second, might, not guaranteed as the spec is limited to 24 fps I believe. If you want it all, then you'll need HDMI 2.0. Color needs a huge amount bandwidth, exponentially speaking.

This, from the horse's mouth:
HDMI.org
"HDMI 1.4b Specification
The major features introduced in the HDMI® 1.4b specification include:

• 4K support enables video resolutions beyond 1080p, supporting high-resolution displays that deliver movie theater-like experiences to the home with incredible depth, detail and color. This includes support for 4096×2160 at 24 Hz, 3840×2160 at 24, 25, and 30 Hz, and 1920×1080 at 120 Hz. All resolutions and refresh rates can be support with the High Speed HDMI Cable."

 

[amey01]

Cripple the color depth and you might get more frames per second, might, not guaranteed as the spec is limited to 24 fps I believe. If you want it all, then you'll need HDMI 2.0. Color needs a huge amount bandwidth, exponentially speaking.

Yes, I know all that.

But WHY do I need 48 gbps of bandwidth to display what is coming in in only 15mbps of a wifi connection ?

 

[RCHeliGuy]

Yes, I know all that.

But WHY do I need 48 gbps of bandwidth to display what is coming in in only 15mbps of a wifi connection ?

Netflix Ultra HD or 4K requires Internet speeds that are a minimum of 25Mbps and 1080p is 10Mbps to send the compressed signal to your decompression box whether it is inside the TV or an external box.

However, if you had a video camera sending RAW uncompressed 4K x 24bit color video for HDR to your TV that would be 6 Gbps at 30fps or 11.9 Gbps at 60fps.

One thing that should be very apparent is that video is streamed with MASSIVE compression that is absolutely lossy and there is not nearly enough bandwidth available to send it anywhere close to uncompressed.

The big question is whether streaming devices offload the decompression to the TV or do it internally. If the streaming boxes are handling all the decompression than the TV is getting a pretty large data load.

Below shows which HDMI versions your TV needs to support different features.
I believe by the time they have reached HDR or 24bit color, they are also in 4K territory.

 

[RCHeliGuy]

For gaming there are actually good reasons for wanting additional bandwidth past the highest currently available.

There are high end VR headsets that are running with more than 4K resolution per eye at up to 90 fps. A few manufacturers have already resorted to using compression/decompression to get what they need across HDMI and DisplayPorts. One manufacturer had to use two DP 1.4 connections to get the bandwidth they needed.

The DP 2.0 spec is s 77.37Gbps data rate, not raw) and was published in 2019. It isn't currently supported by the latest 30 series NVidia GPU's. There are Displayport 2.0 8K gaming monitors being released this year. They will be capable of higher frame rates for gaming but we will be waiting for the 40 series NVidia GPU's likely to be released in the Fall of 2022 to reach their full potential.

I'm not worried about the 8K TV's as I consider that resolution completely wasted, however I am looking forward to new headsets with well over 8K total resolution at higher frame rates for VR headsets. With the lenses that close to your eyes, there is a lot more room for resolving detail. The recent Varjo has a center section of both lenses that is supposed to be a retina display surrounded by a more typical 4K screen. It's pushing an enormous amount of information.