AppleTV 4 surround sound issue

Do HDTVs offer 5.1 channel speaker output now or is this a benefit to those with soundbars? Hard to know what they are thinking because they have zero documentation on surround sound Auto Vs. Dolby.

I am fine with the ATV doing encoding/decoding to benefit those users, but please give those with an AVR the option to turn it off and just passthrough the bitstream.

RufusJazzDog wrote:

Are you saying that I am actually getting the same sound in both cases, despite the different displays on my receiver?

Yes, at this point I think it's safe to say any issues beyond the design of AUTO are configuration errors or faults.

AUTO means:

1) If the input is AC-3 (and nominally E-AC-3) the output is 7.1 LPCM with audio sent to the correct channels

2) If the input is two channel LPCM then it's passed through as two channel LPCM.

The other settings mean force that output without regard to input.

There are some implications but the main operational issue is the apparent change in stream selection given multiple audio streams.

I get the difference between Auto and forcing Dolby Digital. I get the pass through of PCM 2-channel. I don't get your reference to AC-3. What is that? Can the input not be Dolby Digital 5.1? And if it is, why isn't it just passed through like PCM 2-channel?

Do the new update fix the surround issue? I cannot test it right now... ugh! 😟

I tried restoring the factory settings, and then last night an update installed automatically. Neither had any noticeable effect.

Also I have tried careful listening to the same movie, switching back and forth between Auto and Dolby 5.1. So far I cannot hear a difference.

From my testing and all the reading of this thread and several others on the topic, you should be getting the same if source is AC-3 (which is Dolby Digital 5.1 - to answer your Q. to bodosom) and ATV4 setting is auto or Dolby Surround.

I've been following and contributing to the threads (here and at avsforum) on this issue since the weekend of the release. I have a 7.1 setup and was looking forward to finally having 7.1 sound from my collection via ATV.

I'm not familiar with the 2 channel stereo issues because I have a separate 2-channel system not built for A/V (just A) and there is no ATV there.

This being said, I am still not sure if I actually have a problem since I think I haven't run across a verifiable E-AC-3(which is Dolby Digital Plus) 7.1 source that can feed through ATV4. I see via the tvOS that iTunes Terminator Genysis offers DD+7.1 but I cant bring myself to purchase (my opinion here) horrible movie for the sake of testing this. Someone somewhere said they successfully got a DD+7.1 experience after buying that movie through ATV4 (note that is important because on a Mac iTunes only shows a 5.1 version).

I am convinced there is some sort of problem here because at a minimum if I set ATV4 to Auto and send it a verifiable DD5.1 file, I don't thing my AVR should show PCM 7.1 (even though it sounds like a legit DD5.1 soundtrack using 6 speakers).

If anyone can get their hands on a DD7.1 test file in .mp4 format that might answer at least half the outstanding questions....

Same issue here. This used to work perfectly on Apple TV 3.

Nope. Tried it yesterday. No fix.

RufusJazzDog wrote:

Also I have tried careful listening to the same movie, switching back and forth between Auto and Dolby 5.1. So far I cannot hear a difference.

That because there is no difference, there is no problem except one case: if you'r audio sink's surround transforms are limited by input signal you may lose a "feature" if the data is decoded upstream of the sink.

In terms of audio all AC-3 decoding is the same, it's not like inverse telecine or video scaling. In commercial products it's done by licensed and certified parts or licensed and certified software. Back in the day when AC-3 decoders were uncommon decoding in a DVD player was how it was done. On current equipment the difference is the front panel display. Hardly a problem despite the flurry of posts suggesting it is.

Things that can confuse the issue:

1) You are clearly getting the wrong audio -- make sure you're using the correct soundtrack.

2) Channels are wrong -- you have defective ATV or your AVR configuration is incorrect.

I conducted a test between the two settings using the dB Volume app (free for iPhone). I started the movie Star Wars, The Phantom Menace (marque music) for each setting and measured a 2 dB increase for Dolby Surround vs Auto. I am using a Yamaha RX-A1030 with AT4 plugged directly into the receiver.

csmonroe wrote:

I started the movie Star Wars, The Phantom Menace (marque music) for each setting and measured a 2 dB increase for Dolby Surround vs Auto.

Yes there can be gain differences. This may be because of what I believe is the decode/encode used to produce AC-3 or some other minor difference. Likewise the same content sent through your ATV3g versus your ATV4g may play at significantly different levels. It's not a sign of a difference in decoding although if the goal is to minimize recoding/transcoding artifacts it would be better to leave it on AUTO.

Bodosom - any idea where one can find a verified DD+ 7.1 media source/file to confirm the ATV4 is handling correct, besides Terminator G?

meegwell wrote:

Bodosom - any idea where one can find a verified DD+ 7.1 media source/file to confirm the ATV4 is handling correct

I don't believe this is possible. If anyone (Apple, Netflix, HBO etc.) is willing to commit to rear channels then it's simple enough to check. Since Terminator G. was checked that's sufficient to demonstrate that the ATV can generate eight channels of content.

By the way, I don't think the developer guidelines are relevant since I read it as a constraint on app resources not what can be streamed/downloaded by VOD companies.

here is what works for me with my onkyo TX-NR3008, If your movies have multiple tracks like mine one is stereo and the first track in the movie the atv 4 will if set to auto grab the first stereo track and output in pro logic, which is stereo basically, if you set the atv 4 to dolby it will still grab the first track and output in dolby but only the front channels. On some of my movies there is a second track which is the dolby 5.1. First turn dolby digital on in the atv audio menu and then when the movie is playing select the dolby 5.1 track and it will play back all of the channels in true 5.1.