Passthrough audio is finally on the way to Apple TV, iPhone, and more

AppleInsider

We've confirmed at WWDC that tvOS 26 is getting passthrough audio, which could allow a higher quality listening experience by disabling audio preprocessing on the Apple TV hardware, before hand-off to a sound system.

Apple TV 4K

The Apple TV family is a very capable processing device for a set-top box, but one bone of contention has been audio processing. Apple has so far avoided adding passthrough audio features to the Apple TV, but that is seemingly changing.

A reference on the Apple Developer documentation for AVFAudio has an enumeration case for AVAudioContentSource for "passthrough."

Passthrough audio refers to a way that a device or operating system handles audio from a source. Normally, audio from an app, such as Netflix, is processed by the Apple TV, or iPhone before being played to the user.

In the case of a TV or home cinema equipment, they have the capability to actually process audio for themselves. However, since hardware like the Apple TV processes the audio upstream, the original, raw audio stream never gets processed by this hardware.

In effect, even if you have the best possible home cinema system that can handle any audio format or codec in existence, you're going to be stuck hearing whatever the Apple TV has done to the audio.

We've confirmed with Apple that that by enabling the new passthrough audio when it's available and supported by a streaming app, a high-quality audio stream could be left alone by the Apple TV. This allows for hardware after the Apple TV to process the audio, which could give a higher quality result to the listener.

Apple TV audio, and beyond

The main focus of the new Passthrough Audio is the Apple TV, since it is a device that directly interfaces with high-end audio equipment. As a device frequently used for streaming services, this makes it a feature that is mostly focused on improving the Apple TV experience.

However, it's a feature that isn't just limited to tvOS 26. The documentation says the enumeration case for passthrough also applies to iOS 26, iPadOS 26, macOS 26, visionOS 26, and watchOS 26.

Though it is a less useful feature for the Apple Watch, the inclusion on macOS is interesting. Macs are easily capable of being connected up to a TV or home cinema hardware, and can be used to play back media in the same way as Apple TV.

The inclusion of an enumeration case is a good sign that the audio feature has become a reality, but it's still far from being useful. Developers now have to take advantage of the enumeration case so that it can work with their apps.

It may also require Apple to actually add a setting to enable passthrough or to force Apple TV to handle audio processing. A check of the first developer beta of tvOS 26 doesn't include the option in the Settings app's audio section.



Read on AppleInsider

applezulu

Interesting. Would this mean that, assuming you have the right audio gear downstream, an existing AppleTV 4K could play Apple Music at full 24-bit/192 kHz resolution, simply by sending the audio straight through? That would be nice.

williamlondon

This is interesting, would HomePods do anything different to the signal they receive now when they output? Wonder if this means they might take advantage of it with their own existing products, or introduce new products that will?? Fun times.

chrisfitz

So a couple of questions

If I have 4K UHD rips with Dolby TruHD audio, that I currently watch on Plex on my Nvidia Shield, does that mean that the Apple TV will just pass that through, so I get Dolby Vision and lossless Dolby audio?

Also does that mean that Apple is going to pump up their audio on the store for purchases and rentals to lossless?

mike wuerthele

chrisfitz said:

So a couple of questions

If I have 4K UHD rips with Dolby TruHD audio, that I currently watch on Plex on my Nvidia Shield, does that mean that the Apple TV will just pass that through, so I get Dolby Vision and lossless Dolby audio?

Also does that mean that Apple is going to pump up their audio on the store for purchases and rentals to lossless?

1) Streaming apps will need to be updated first, but yes.

2) No idea.

mike wuerthele

williamlondon said:

This is interesting, would HomePods do anything different to the signal they receive now when they output? Wonder if this means they might take advantage of it with their own existing products, or introduce new products that will?? Fun times.

I don't think this is going to change. AirPlay is pretty static, and there's no sign of an AirPlay 3 this year.

lotones

If I can stream hi-res audio from Apple Music or from my Mac I'll be very happy. At the moment I have to stream hi-res audio from my Mac through my disc player's inferior interface. Sounds great, but it's clunky. But it was made in 2016, so it's about time Apple TV caught up.

And it would be nice to consolidate all my hi-res music into the Music app and stream it from there.

edited June 10

chrisfitz

Mike Wuerthele said:

chrisfitz said:

So a couple of questions

If I have 4K UHD rips with Dolby TruHD audio, that I currently watch on Plex on my Nvidia Shield, does that mean that the Apple TV will just pass that through, so I get Dolby Vision and lossless Dolby audio?

Also does that mean that Apple is going to pump up their audio on the store for purchases and rentals to lossless?

1) Streaming apps will need to be updated first, but yes.

2) No idea.

Looks like I am finally going to buy that AppleTV I have put off for the Shield the last couple of years.

Thanks

jonro

I think this means that macOS or iOS will pass Dolby Atmos directly to Sonos speakers. Anyway, I hope so. 

mike wuerthele

jonro said:

I think this means that macOS or iOS will pass Dolby Atmos directly to Sonos speakers. Anyway, I hope so. 

Probably not. It's the nature of AirPlay 2 that won't do it.

locutus

We may be getting ahead of ourselves here.  This is likely just including other platforms in the macOS passthrough API included in macOS last fall.  The API offers limited passthrough support for DD and DD+.  In macOS, it's a per-app preference.  Its not a guarantee.  When set, macOS will passthrough audio as long as you don't have any other audio features in use that requires macOS to decode the audio.  Once you do, macOS falls back to decoding rather than passing through.  macOS doesn't support TrueHD or DTS with this change.  I don't imagine tvOS will either.

edited June 10

rogue01

williamlondon said:

This is interesting, would HomePods do anything different to the signal they receive now when they output? Wonder if this means they might take advantage of it with their own existing products, or introduce new products that will?? Fun times.

No.  HomePods are WiFi only and audio passthrough is over HDMI connected to a Home Theater surround receiver, so the receiver's Dolby circuitry can handle the Dolby TrueHD or Dolby Atmos processing, rather than the AppleTV handling the audio processing.  The HomePod is just a speaker.

rogue01

jonro said:

I think this means that macOS or iOS will pass Dolby Atmos directly to Sonos speakers. Anyway, I hope so. 

No.  This is HDMI passthrough for an AV receiver to handle the processing, not a Sonos speaker over WiFi.

rogue01

Finally an update to AppleTV that is worth getting excited for.  An AV receiver will do a much better job with the sound processing than the AppleTV.  I did not realize the AppleTV wasn't already doing the passthrough over HDMI for a receiver to handle the processing.

locutus

Rogue01 said:

Finally an update to AppleTV that is worth getting excited for.  An AV receiver will do a much better job with the sound processing than the AppleTV.  I did not realize the AppleTV wasn't already doing the passthrough over HDMI for a receiver to handle the processing.

Almost no mainstream streaming player fully passes through audio.  The Roku Ultra allows it for DD and DD+ only.  The Shield will for some formats, but it's not really mainstream.

edited June 10

mike wuerthele

Locutus said:

We may be getting ahead of ourselves here.  This is likely just including other platforms in the macOS passthrough API included in macOS last fall.  The API offers limited passthrough support for DD and DD+.  In macOS, it's a per-app preference.  It's not a guarantee.  When set, macOS will passthrough audio as long as you don't have any other audio features in use that requires macOS to decode the audio.  Once you do, macOS falls back to decoding rather than passing through.  macOS doesn't support TrueHD or DTS with this change.  I don't imagine tvOS will either.

Apple says it isn't the same, but we'll see. The previous call still exists.

locutus

Mike Wuerthele said:

Locutus said:

We may be getting ahead of ourselves here.  This is likely just including other platforms in the macOS passthrough API included in macOS last fall.  The API offers limited passthrough support for DD and DD+.  In macOS, it's a per-app preference.  It's not a guarantee.  When set, macOS will passthrough audio as long as you don't have any other audio features in use that requires macOS to decode the audio.  Once you do, macOS falls back to decoding rather than passing through.  macOS doesn't support TrueHD or DTS with this change.  I don't imagine tvOS will either.

Apple says it isn't the same, but we'll see. The previous call still exists.

Hmmm, If its not the same, it will be interesting to see how some accessibility features, Siri, multi-room audio,...etc, still function as they do today without the audio being decoded first.

edited June 10

mike wuerthele

Locutus said:

Mike Wuerthele said:

Locutus said:

We may be getting ahead of ourselves here.  This is likely just including other platforms in the macOS passthrough API included in macOS last fall.  The API offers limited passthrough support for DD and DD+.  In macOS, it's a per-app preference.  It's not a guarantee.  When set, macOS will passthrough audio as long as you don't have any other audio features in use that requires macOS to decode the audio.  Once you do, macOS falls back to decoding rather than passing through.  macOS doesn't support TrueHD or DTS with this change.  I don't imagine tvOS will either.

Apple says it isn't the same, but we'll see. The previous call still exists.

Hmmm, If its not the same, it will be interesting to see how some accessibility features, Siri, multi-room audio,...etc, still function as they do today without the audio being decoded first.

I don't think it's either/or. We'll see how it goes when it rolls out in full. It doesn't do anything now, and will require Apps to get updates.

speedgarage

One reason for Apple to decode audio rather than pass thru would be to mix in UI sounds. I Don’t recall if Apple TV currently generates UI sounds while playing back DD/DD+ content tho.  Other than that, I’m not sure why Apple TV would not just pass thru audio by default (assuming downstream device can decode format)

locutus

speedgarage said:

One reason for Apple to decode audio rather than pass thru would be to mix in UI sounds. I Don’t recall if Apple TV currently generates UI sounds while playing back DD/DD+ content tho.  Other than that, I’m not sure why Apple TV would not just pass thru audio by default (assuming downstream device can decode format)

There are many instances where audio is mixed in while content is playing.  The Apple TV has audio overlays with some accessibility features. These occur while audio is playing.  In addition, Siri lowers the audio when the Siri button is pressed.  This is done so the content audio isn't heard and interpreted by Siri.  In addition to all that, AirPlay 2 multi-room audio requires Apple to decode the audio.  Multi-room audio is likely the reason why Apple plugged the "hole" in the first place that allowed some third party apps to bypass tvOS's audio pipeline and passed through  audio.  The "hole" was plugged in tvOS 11.3.  Multi-room audio was released two months later in 11.4.

jeffharris

chrisfitz said:

Mike Wuerthele said:

chrisfitz said:

So a couple of questions

If I have 4K UHD rips with Dolby TruHD audio, that I currently watch on Plex on my Nvidia Shield, does that mean that the Apple TV will just pass that through, so I get Dolby Vision and lossless Dolby audio?

Also does that mean that Apple is going to pump up their audio on the store for purchases and rentals to lossless?

1) Streaming apps will need to be updated first, but yes.

2) No idea.

Looks like I am finally going to buy that AppleTV I have put off for the Shield the last couple of years.

Wait for an updated Apple TV 4K that supports passthrough audio before buying.
Clearly, if I'm reading the article correctly, the existing version does NOT do that.

I have 2 Apple TV 4K. The one connected to my main A/V system I'd definitely update for passthrough audio.

edited June 11