Apple Broke Dolby Digital 5.1 Output on Apple TV 4K

The problem was solved with the latest update released for the Apple TV 4K.

I signed up on Apple's website to also receive beta updates and then the option to download a beta version on the streamer itself was opened. I downloaded an update and the problem was solved. At first, I manually enabled the Dolby Digital 5.1 option in the settings, then I set it back to auto, after I saw that it was indeed playing Dolby Digital. When I put it back to auto, it now knows how to play Dolby Digital with the appropriate content and Dolby Atmos with the appropriate content. very happy!

[Edited by Moderator]

You have a valid point. PCM does not mean 2.0. I like your troubleshooting which makes sense. However, a lot of AVR's especially newer ones will upconvert a 2.0 signal automatically and indicate it is running through as many speakers/channels as the AVR can handle.

Example, AVRs could take a 5.1 and turn it into 7.4.2 (Atmos). Does your AVR have a "STRAIGHT," or "DIRECT" mode? What these modes will do is it passes the sounds through directly as the source puts out. I tested the same way you did, at first, I was like, "who cares if it displays PCM as long as it works correctly," until I realized it didn't work correctly. I did not put my AVR on "DIRECT." When I did, it indicates a 2.0 signal coming into the receiver (showing only the Front L/R was being used), and it was my AVR that upconverted into 7.4.2 when it wasn't in DIRECT. I came to this conclusion because I tested the AppleTV 4K box even when it showed all channels were active, it sounded funny, so I then used the native AppleTV application on my LG TV, the decoding was correct, and the sound was much, much fuller, even at the same volume, using the same movies. I have also tested with other services such as Netflix using AppleTV 4K box vs Apple TV application on the LG TV. When I switched both test to DIRECT, the ATV4K Box, was simply upconverting 2.0 lossless. (top photo is AppleTV Box, bottom is native AppleTV app on LG TV, 3rd photo is in DIRECT mode with the display set to indicate the channels used).

When I use my LG AppleTV application, it will pass through all channels indicated much like your screen shot (showing all the speakers being utilized, I apologize, to save time, I did not screen shot everything). When using "STRAIGHT," or "DIRECT" with the AppleTV 4K, it indicates only 2 channels. Please see screenshot. Please let me know if you have a DIRECT/STRAIGHT/PASSTHRU mode on your receiver and what your results are.

I have one of each: Apple TV 4K and Apple TV HD. What I want to try to make clear is that both models have the problem under tvOS 18.0. Neither had the problem under the most recent previous release. The problem I'm referring to is that when the Audio Format is set to

Change Format: On

New Format: Dolby Digital 5.1

no multichannel output goes out of the devices through HDMI or S/PDIF.

(I think I neglected to use the phrase "New Format" in my previous posts. Sorry.)

Remember, when you set Change Format to Off, the 2nd option (the option to assign "New Format") is no longer available. Then the Audio Format setting defaults to Auto. The Auto setting allows both models of Apple TV to send 5.1, but only if the AVR, or Sound Bar, or whatever sound system connected synchronizes with the Apple TV in such a way that the Apple TV recognizes that sound system and sends multichannel audio. AFAIK, there's no published list to reveal what sound systems allow Apple TV to sync and sent multichannel audio when the Auto setting is active.

If you want to observe the problem, just make these settings in Audio Format from the Audio section of Video and Audio in Settings:

Change Format: On

New Format: Dolby Digital 5.1

Then play a multichannel audio title from a streaming app other than Home Sharing or YouTube. The output will only be stereo (2-channel).

I hope that is a useful explanation.

This happened to me too. I found my fix, but it's not ideal, and it's not going to work with all audio setups.

First, we need to understand how Apple TV handles audio output. By default, Apple TV decodes Dolby Digital (Plus) 5.1 or 7.1, and send the signal out as Multichannel PCM. It does the same thing for Dolby Atmos as well, but when it's Atmos, it also sends out the Atmos metadata so our Atmos capable device will recognize it and process it accordingly. If you change the "audio format" setting on Apple TV, then it will re-encode the PCM audio back into Dolby Digital 5.1 only, hence Dolby Atmos is no longer available in that case.

My set up prior to TVOS 18 was connecting Apple TV directly to my eArc capable TCL TV, and the TV is connected to Samsung soundbar via eArc. Before the update, Apple TV was able to detect my TV's passthrough ability, so it will actually only re-encode multichannel PCM into Dolby Digital when Atmos isn't available even when Apple TV's audio output setting was at default! Then, when Atmos is available my TV will pass it through to the soundbar as it is.

Nevertheless, that smart detection is no longer there after TVOS 18. Now, with the old setup, Apple TV can only send multichannel PCM to my TV, while my TV can't passthrough multichannel PCM, so the soundbar will only receive stereo PCM.

My fix is that I now connect the Apple TV to one of my Samsung soundbar's HDMI inputs, as my soundbar has no problem processing multichannel PCM directly, but it's not ideal because my soundbar tends to process multichannel PCM at a much lower volume. This fix won't work for everybody either, because a lot of sound systems on the market today are meant for you to use your TV's eArc ability. For example, if you have the latest Bose or Sonos soundbar, it only has a single eArc HDMI input.

The latest TVOS 18.1 fixed mine. My AV receiver is ancient Yamaha DSP-Z7 that supports hdmi 1.3 and DD/DTS (no DD+ or Atmos). It seems like the new update fixes DD 5.1 but still has a problem with DD+ or ATMOS (specifically when the source is DD+ Atmos and the sound output is set to AUTO, not forced to DD 5.1)

Content that is flagged as Dolby Atmos plays as Atmos and is reported as such by the soundbar display. 5.1 used to show as Dolby Audio with sound coming from all channels. Now it reports PCM and sound only from the left and right front channels. Play the same content on the TVs on board ATV app and it plays as Dolby Audio complete with centre and rear channel sound.

I think i found a work around. I have apple tv hd (not 4k) but maybe works for others. I have my apple tv hooked to the tv via hdmi and from the tv to the home theater receiver via spdif optical cable. I also have a homepod mini. So i click on the apple remote top corner to get the audio options and temporarily switch output to the homepod mini, then switch to multispeakers both homepod and tv speakers (spdif) and finally switch back to ONLY tv speakers spdif. This seems to cause apple tv to “reset” the audio signal and my theater receiver then gets dolby 5.1 normal as it used to. Tried it yesterday and today and seems to work everytime i cycle outputs as described above.

Same thing happened to me after the tvOS 18 update on my Apple TV HD. I change the audio output in Settings to force Dolby Digital 5.1 for my speakers (Logitech Z906). I pass my audio from the tv to the speakers with a TOSLINK optical cable.

A fix that worked for me. I temporarily switched my audio output to my HomePod mini from the Control Center and then switched back to TV speakers. Now I am getting a 5.1 signal. It works with AirPods too. As long as you switch the audio output to something else and then back to TV, it seems to correct itself.

Definitely a bug that Apple needs to fix.

I was quite fortunate to have 2 x individual 4K Apple TV pucks. One of them updated to TVOS 18 resulting in a loss of DD5.1 via my Yamaha AVR. The other remained on TVOS 17.6.1 and still supported DD5.1, so I was able to switch the pucks over.

note to self: Disable auto updates. Only update one and review for bugs.

The b version has fixed it the issue for me, but still keeping the other on 17.6.1 until the official update is pushed out for me to review.

Thank you to those of you that started of the thread, and reported to A HQ.

18.1 solved my the DD 5.1 issue for me as well. Didn't have to mess with any settings or anything, just started outputting 5.1 automatically as it should.

Another update: I've just had another experiment. I played "Octopussy", a film with a DD5.1 soundtrack. Played directly from the Apple TV is plays in PCM 2 channel stereo. Selecting the same film in the TV app on my iPhone and using Air Play to cast it the Apple TV, it plays in DD 5.1.

I have updated to the version that must not be mentioned here. I can confirm that the issue is resolved for me with a 1st Gen 4k box going into an LG C1 then HDMI (earc) to LG SN9YG Atmos soundbar. Atmos works (as it always did) and Change Format gets me DD5.1 again instead of PCM Stereo. I’m sure the fix will carry on to the public release of 18.1🤞🏻so hopefully not too much longer to wait.

Correct Payton. So far it continues to work for me. Not the best solution, but works until an actual fix is released.

For instance, i go into netflix and choose a movie (not play it yet). Choose both tv speaker and homepod. Play a bit of the movie in stereo only. Get out of the movie back into the movie menu. Change the audio to turn off the homepod audio leaving only the tv speaker. Play the movie again and dolby comes on. It stays on as long as I dont leave netflix app. If i change to any other app like apple library or Max or Amazon movies, dolby goes away but just repeat the same process of switching speakers and comes right back.

Finally, it’s fixed in tvos 18.1! Just confirmed.