Audio dropouts/pauses for new Atmos enabled music on Apple Music, played back over AppleTV 4K gen.2

[Paul Cordingley]

Like CDs, Blu-ray Discs are one long continuous spiral, and any chapter breaks are purely notional. In the case of a CD they are read from the TOC (table of contents) for example.

For streaming music, the case will be different. Each track will be a separate unique file, and they start and stop as such, hence the pause between them. Whether they are part of an "album" or a compilation, they are pulled together as a play list.

I do agree however that surely it's possible to tie the songs together when their play order is known ahead of time, but I accept that it's probably not trivial.

 

[Bruins96]

Like CDs, Blu-ray Discs are one long continuous spiral, and any chapter breaks are purely notional. In the case of a CD they are read from the TOC (table of contents) for example.

For streaming music, the case will be different. Each track will be a separate unique file, and they start and stop as such, hence the pause between them. Whether they are part of an "album" or a compilation, they are pulled together as a play list.

I do agree however that surely it's possible to tie the songs together when their play order is known ahead of time, but I accept that it's probably not trivial.

It has to be possible, because when you stream the *non Atmos* versions of the album, there are no pauses between the tracks.

The functionality was called "gapless playback". When iTunes first came out and I ripped a bunch of CDs (including Abbey Road) to it, the pauses between tracks were there. Then the first "workaround" Apple came up with was a user could go to their iTunes library and designate songs that ran into each other. Which was a chore but some of us bothered to do it. Then eventually they enabled "gapless playback" and the issue largely went away.

Until Atmos support on ATV4K.

 

[Paul Cordingley]

Right, but there's a gulf between simple two-channel stereo and multi-channel stereo combined with n-objects which requires setup of those objects, fetching/cacheing and so on. Again, I imagine it is possible but far from trivial.

 

[Crunchynut]

Two observations from me that might help with the puzzle. Firstly, if streaming an album (of discrete tracks) downloaded to iPhone or iPad, the problem of the first second of a track being silent does not always occur on every track - just some tracks. So if it’s do do with the stream transport or DAC deciphering what it’s being sent before locking, that doesn’t figure (unless, may be, sometimes lock is lost and sometimes it isn’t). Secondly, I did a test tonight comparing streaming to an iFi Zen Stream or a 3rd gen Apple TV, and both exhibited the effect. I intend to feed a different DAC to see if that is the common problem.

 

[Bruins96]

Right, but there's a gulf between simple two-channel stereo and multi-channel stereo combined with n-objects which requires setup of those objects, fetching/cacheing and so on. Again, I imagine it is possible but far from trivial.

I am no software engineer so I fully admit I could be talking out of my ...

But I do think cacheing will/should likely play a role. Having downloaded Atmos tracks to my iPhone, they're not that huge per song track (I want to say they were around 20-60MB each (I'm looking at my Abbey Road Atmos download folder on my iPhone, Come Together is 33.7MB and I Want You (She's So Heavy) is 60.5MB). I know people can load their Apple TVs with a bunch of apps and games, but my 64GB version has less than a dozen apps and no games, so in theory it could preload the entire album with ease, let alone simply downloading the next one or two tracks to facilitate cacheing. And all my streaming devices are hardwired to my 400mbps internet so I know it's not an internet speed issue.

Interestingly, speaking of the Atmos files on my iPhone, playing them results in no initial pause/dropout (i.e. skipping around to any track doesn't result in any audible dropout. ***But*** when you play the medley (i.e. start with Mean Mr. Mustard to Polythene Pam to She Came In Through my Bathroom Window) if you listen very carefully there is a split second, and if I had to guess I'd say it is like 1/100th of a second or less, where you can hear just the faintest tick of a dropout. Nowhere near what you hear on the ATV4K to a receiver which is an easily audible dropout that's closer to maybe 1/10th of a second. But if you listen closely it's there.

So maybe Apple and its engineers haven't fully worked out how to do encode and play gapless tracks using the Atmos codec.

Here's another interesting thing I've just discovered. I went to the Atmos Sgt. Peppers version on my iPhone and you can hear that 1/100 (maybe 1/1000th) of a second barely audible pause between Sgt. Peppers (Reprise) and A Day in the Life, two tracks which should seamlessly blend together.

So my thought was "aha, maybe this is Atmos *and* a high-res lossless CODEC issue!"

But then I went to the Hi-Res Lossless of The White Album. The part where Back in the U.S.S.R. blends into Dear Prudence? Seamless. Gapless. Listen to the jet engine blend straight into the arpeggiated guitar. I played it back a half dozen times. No microsecond gap. It is possible.

(PS all these tracks/codecs I'm referring to are downloaded to my iPhone 12 Pro Max from my Apple Music subscription)

 

[Oliver_reid]

I am seeing similar issues playing ATV into Arcam AVR.

Happens also with the ATV connected directly to my LG OLED tv


"The Long and and Winding Road" track has zero lead in time and if I the select track directly the first word I hear is "..inding".

If you allow the album to play through track to track the may be a very quick drop out but at least you hear all the words

See this movie

 

[TsMkLg068426]

Good to see that I am not the only one having this issue when playing Dolby Atmos audio on Apple Music with my Bose Lifestyle 650 system even though it does not support Dolby Atmos it is backwards compatible meaning it would play 5.1 Dolby HD instead.

The worst part about the audio issue is not just audio stopping or pausing it starts making loud pop noises on my Soundbar and continues to affect all my other devices connected to my Bose receiver. The only fix I found is turning off everything connected on the power outlet and restarting which is really a pain in the ass.

Apple has serious explaining to do here because this issue is serious and a real problem for those with sound systems.

 

[Bruins96]

Thanks for posting the video Oliver. That's one of the two phenomena I have been constantly harping on Apple to fix (the other is gapless playback support, evident as gaps in what should be continuous music as one track blends into another on "The Medley" side of Abbey Road...if Pink Floyd's most popular albums are ever put in Atmos it will be a problem for a lot of those songs as well...can you imagine a pause between all those tracks that run into each other in The Wall or Wish You Were Here).

Just my semi-regular update to say, another beta released...and issues are still not fixed (latest 64GB ATV4K via HDMI 2.1 48Gbps cable to Denon 4500h AVR). I keep updating my Apple Feedback ticket with every build...but I'm starting to think they're ignoring it by now...

 

[ATV#2022]

I've been facing similar issues when playing Contents via my Apple TV 4K, especially with Netflix, the audio dropout on my SONOS HT happens randomly. At first I thought I've accidentally changed the audio settings on my Apple TV or on my smartTV itself. After checking, found all connections were ok. I then checked and recaliberated my SONOS speakers but the issue still persisted, checked for firmware update on both AppleTV and SONOS, none found. Then I played Netflix directly from my smartTV and was playing perfectly well. Now I know that Apple TV is the culprit, I hope they will resolve this issue quickly.

 

[Bruins96]

And still not fixed on tvOS 16 beta 1. Although I stumbled on an interesting workaround for the initial dropout glitch...if I stream the ATV4K directly to the TV, and then use eARC to the Atmos receiver, I don't seem to be losing that split second when a song first starts. Now I've only just recently done this so I've only been able to test a few tracks, but the infamous missing first bass notes of The Beatles "Come Together" in Atmos are all there. My guess is that the TV, once sensing Atmos, is pre-sending an Atmos signal to the receiver so it's "ready" for the incoming first song.

However as soon as you get to the medley of Abbey Road, the lack of gapless support is still evident by gaps of silence between songs that should run together. And noticeably those gaps are longer when using the ATV to TV to eARC Atmos receiver playback chain. So while it apparently helps with the initial signal detection dropout, it worsens (or exacerbates) the lack of gapless playback support.

I listen to a lot of classical on Apple Music in high res stereo over headphones, but I also see the Spatial Audio/Atmos logo on many of these amazing sounding performances. So there is a concerted effort to get a lot more music on Spatial Audio/Atmos, but clearly Apple prefers you listen to that on their playback chain (meaning using their AirPods and Beats headphones) versus using a 7.1 non-Apple Atmos audio playback system because if they valued the latter, there's no way these glitches would be allowed to come out on a release version and be unaddressed for so long.