Apple TV 4 Dolby Surround

since we all seems to have same issues.

Yes, there are many different opinions—depending on whose response you are reading and how they interpret the indicators on their home theater systems.

What are the best setting for now.

For the most part, I believe this to be a matter of personal preference. On my system all three settings (Auto, Dolby Surround, and Stereo) appear to work correctly for their intended purpose (as I understand them). Unfortunately, these settings do affect a user's AVR or HDTV playback indicators which seems to be the major area of controversy. In addition, audio content actually being played back can further confuse the issues. Therefore, for the purpose of my discussion/descriptions, I am limiting my observations to videos with stereo AAC and mono, stereo, DD PL2, or 5.1 AC3 ("legacy" Dolby Digital) encodings and not DTS, DD+, or TrueHD 7.1 content—formats of which I have yet to find valid 8-channel sample files that can be imported into my iTunes media library for testing. Lastly, if you find a setting you like that is working they way you want/expect, don't change it arbitrarily. Settings have habit of sometimes "freezing" in one mode even though the menu indicates you have changed to another mode.

What you all try and result

For me, the best "Surround Sound" setting is "Dolby Surround" since it allows my AVR indicators to accurately mirror the actual AC3 encode and speaker output activity. The only major problem I have is an inaccurate AVR display when/if I forget to re-select the AC3 track each time I open a new file. You can reset internal video file flags to automatically select the AC3 track and/or hide a secondary AAC track, but another responder has said this may cause metadata loss. Besides, Apple may correct this issue and I am not anxious to modify thousands of files prematurely if I don't have to do so.

Basically, the "Auto" setting seems to send the source track audio to the AVR or HDTV over a PCM HDMI connection and lets the receiving device deal with it. In this case the stereo AAC data is sent as stereo PCM as with older TV devices but the AC3 data is sent using a 7.1 PCM HDMI connection that incorrectly triggers a display of all PCM surround channels but correctly plays the active audio channels on my system as originally encoded. Others may get different speaker output results here depending on whether or not they have 6-channel fallback capabilities programmed for 8-channel connection and how Apple is actually sending the AC3 data.

On the other hand, the "Stereo" setting seems to unconditionally output everything (mono and stereo AAC or mono, stereo, and surround AC3 audio as PCM stereo.

While I believe there are definitely several issues to be addressed, I can at least live with my current TV4 settings as they are compatible with my older TV2 and TV3 devices, as well as, all of my files as they are now encoded. If you have a problem setting up and/or testing your settings configuration, and you have an iPhone or iPad handy, you may want to download Jeff Perrin's free Speaker Check for Apple TV app utility. I used it to cross check my TV4 and AVR visual activity indicators with what I am actually hearing from the individual speakers since so many people were saying so many different things.

I know you are not considering DD + 5.1, but that is the format that Netflix uses. Is the apple TV decoding or passing this through? I only see DD on my Onkyo so it makes me think that the ATV is converting the Netflix bitstream to DD. This is so confusing.

Kudos to you by the way. Your posts are providing more info than Apple's failure to document Auto Vs. Dolby Surround.

Agreed! I too would like to understand how / where Netflix DD+ is being handled or if its just not being output from the Apple TV 4 for now. For now, I'm finding the Dolby Surround setting to work best for my set up.

I know you are not considering DD + 5.1, but that is the format that Netflix uses.

Did not originally include DD+5.1 because I did not have any such encodings to test at that time. Have since created a DD+5.1 audio track wrapped in an M4V file from a 6-channel WAV source file using Compressor because all Dolby Digital files (from DD 1.0 thru DD 5.1) appear as DD+7.1 content on my AVR in the "Auto" mode and appear "as encoded" in the "Dolby Surround" mode under the tvOS v9.0 operating system. (I.e., I can't really differentiate DD+ file from DD file unless it's encoded as 7.1 content.)

Is the apple TV decoding or passing this through?

On my system under tvOS v9.0, all Dolby Digital encoded content appeared to be passed through to the AVR in both the "Auto" and "Dolby Surround" modes and was correctly decoded and played back through correct speakers as originally encoded. (I.e., the Dolby Digital decoder was automatically activated even though one or more of the Direct/PCM Direct/Stream Direct indicators is also active.) The only difference between the "Auto" and "Dolby Surround" modes was that my AVR unconditionally indicated the audio was encoded as DD+ 7.1 content in the "Auto" mode while in the "Dolby Surround" mode the AVR correctly indicates which channels were originally encoded with active content.

Under tvOS v9.0.1, in the "Auto" mode, the Dolby Digital source track is now delivered to my AVR as 7.1 Direct Stream PCM with a secondary PCM indicator lit instead of the DD Digital decoder indicator being lit. Based on this, it would appear decoding is actually performed by the TV4 under this update. In addition, DD 1.0, DD 2.0, and DD PL II encoded content is delivered as if it were in the "Stereo" mode (2-channel PCM delivery connection) and remains "stuck" in this mode even when the TV4 is switched to the "Dolby Surround" mode. Further, the "Computers" app appears to only reset/restore itself to correct "Dolby Surround" operation if/when a Dolby 5.1 audio source is detected by the TV4. For this reason, I now leave my TV4 set to "Dolby Surround" mode except for when running tests.

I only see DD on my Onkyo so it makes me think that the ATV is converting the Netflix bitstream to DD.

As I implied above, my AVR indicators depend on the source track content, specific TV4 mode, and AVR mode settings. For instance for a Netflix 5.1 (50 First Dates) and 2.0 (Charade) movie, my AVR indicators are as follows:

NOTE 1: Switching to the TV4 "Dolby Surround" mode after using the "Auto" mode in the Netflix app DOES NOT get "stuck" in the 2-channel PCM output mode like the Computers app does.

NOTE 2: Base on my AVR audio indicators, it appears the Charade video used for testing is probably an older Netflix file encoded with a non-Dolby audio track.

Great info, Jon. I ended up returning my Apple TV 4th-gen due to this issue and the related problem of having to go back and modify all of my AC3/AAC dual-track containing files.

My problem is my Sony AVR is typically set to enhance 5.1 DD to fill my 7.1 system when the AC3 DD5.1 is passed along in "Dolby Digital" mode. Because the ATV4 with tvOS 9.0.1 passes along all surround sound as PCM 7.1 when in "Auto" mode, all my DD5.1 leave the rear channels empty in this mode. Similarly, as you note, I've come across the ATV getting stuck passing stereo mode with other sources when set to "Dolby Digital" mode. There's an argument to be made about playing back the audio strictly as encoded vs. filling all the speakers, but that's why there are different settings on my AVR... ;-) I don't like being stuck with two choices with ATV4 that both don't work right, in that respect.

Get ATV back to passing along the original audio streams to the AVR, so it can handle any processing (or not) of the sound field, get it to handle AC3/AAC dual-audio tracks like every other OS X and iOS device, and get Siri searching local content and I'm happy to jump back to ATV4. It's got a lot of potential! But as it is, my ATV3 works better right now.

Oops! Need to correct the following in my Nov 15, 2015 post above :

For items 6 thru 8 in both columns, the header "TV4=Auto" entry should read "TV4=Dolby Surround" in all instances. (Sorry, used a copy-paste workflow to enter the "headers" but only corrected the item 5 entries after pasting.)

Jon Walker wrote:

On my system under tvOS v9.0, all Dolby Digital encoded content appeared to be passed through to the AVR in both the "Auto" and "Dolby Surround" modes and was correctly decoded and played back through correct speakers as originally encoded. (I.e., the Dolby Digital decoder was automatically activated even though one or more of the Direct/PCM Direct/Stream Direct indicators is also active.)

Under tvOS v9.0.1, in the "Auto" mode, the Dolby Digital source track is now delivered to my AVR as 7.1 Direct Stream PCM with a secondary PCM indicator lit instead of the DD Digital decoder indicator being lit. Based on this, it would appear decoding is actually performed by the TV4 under this update.

I've seen no change in behavior after the update and it's not possible to have PCM and bitstream at the same time. If your AVR is indicating that then it's a code for some other process or result.

Since the dialnorm meta-data is removed in DOLBY mode it's clear that, with my AVR, the TV 4gen is decoding and optionally re-encoding (incorrectly) all audio data. I imagine this behavior could be AVR specific but it seems unlikely.

I've seen no change in behavior after the update and it's not possible to have PCM and bitstream at the same time. If your AVR is indicating that then it's a code for some other process or result.

Am surprised that you have not noted any change in behavior after the update—especially the "sticking" of TV4 output in the "Stereo" mixdown mode following playback of say a mono center channel AAC or AC3 track in the TV4 "Auto" mode, switching to the TV4 "Dolby Surround" mode and continuing playback of the same or different AAC/AC3 1.0 or 2.0 audio track content use the "Computers" app as the player.

If you review my actual tabulated information, you will not find any instance where PCM and DD Digital indicators are both simultaneously lit. However, my statement that "the Dolby Digital decoder was automatically activated" may, admittedly, have been confusing. What I actually meant was that under the original tvOS v9.0 in the "Auto" mode, AC3 1.0, 2.0, and Dolby PL II track content was automatically decoded and played back through the speakers as it was originally encoded despite my AVR unconditionally indicating 7.1 channelization. Under tvOS v9.0.1, such content appears to be decoded by the TV4 using a "Stereo" mixdown strategy and sent to my AVR as "Stereo" (primary indicator) content with PCM (secondary indicator) lit and no graphic channelization display. Further, as discovered by many users, the TV4 can become "stuck" in this output mode under certain conditions until refreshed/reset by a Dolby 5.1 signal in the "Dolby Surround" mode. Other apps like Netflix, Air Video HD, Surround Speaker Check, Theater Test, etc. do not appear to have this issue.

Since the dialnorm meta-data is removed in DOLBY mode it's clear that, with my AVR, the TV 4gen is decoding and optionally re-encoding (incorrectly) all audio data.

Under tvOS v9.0.1 until yesterday afternoon, I probably would have agreed with this statement. However, a new twist seems to have been added. While comparing the playback of an M4B mono and stereo audiobooks, I discovered that center channel mono AAC audio files are now playing correctly through the center channel speaker when the TV4 is set to the "Dolby Surround" mode. That is, the mono center channel AAC audio now appears to be correctly encoded as center channel mono audio on the Dolby 5.1 signal being sent to my AVR with other audio channels empty. Previously under tvOS v9.0.1, such content was incorrectly encoded as 2-channel audio playing back through L & R speakers rather than the current center channel speaker. Since I had originally used the King Kong (1933) M4V file to test "mono" AAC and AC3 playback in the TV4 "Dolby Surround" mode using the "Computers" app, I immediately retested that file and reconfirmed that its AAC center mono audio also now played correctly using the aforementioned settings. Am confused as to what may have happened here. The tvOS version in use is still v9.0.1 and I can find no indication that the "Computers" app itself has auto-updated. Can any else confirm this change in TV4 "Dolby Surround" playback? AC3 center mono playback continues to play normally with the original Dolby 1.0 audio being being "passed through" to the AVR for decoding of just the original active channel (i.e., no "empty" channel display as with an "DD5.1 encoded" AAC 1.0 or 2.0 source track).

Jon Walker wrote:

1) Am surprised that you have not noted any change in behavior after the update—especially the "sticking" of TV4 output

2) Under tvOS v9.0.1, such content appears to be decoded by the TV4 using a "Stereo" mixdown strategy and sent to my AVR as "Stereo" (primary indicator) content with PCM (secondary indicator) lit and no graphic channelization display.

Since the dialnorm meta-data is removed in DOLBY mode it's clear that, with my AVR, the TV 4gen is decoding and optionally re-encoding (incorrectly) all audio data.

3) Under tvOS v9.0.1 until yesterday afternoon, I probably would have agreed with this statement.

1) I'm content to check material in my library. That's two-channel AAC and 5.1 channel AC-3. I see no changes with that content in 9.0.1 vs. 9.0.

2) I don't understand this. Are you saying AC-3 content in AUTO mode is rendered the same as AC-3 content in STEREO mode?

3) I still see the same behavior -- dialnorm is removed from AC-3 encoded files in DOLBY mode. Saying all audio data was wrong since I haven't tested all possible input formats.

1) I'm content to check material in my library. That's two-channel AAC and 5.1 channel AC-3. I see no changes with that content in 9.0.1 vs. 9.0.

As am I. However, my library includes theatrical serials, movies, and TV shows sampled over an 89 year period and includes AAC and AC3 1.0, 2.0, stereo, and Dolby ProLogic II, as well as, AC3 5.1 audio encodings. Since, by your own admission, you are only testing a limited subset of encoding possibilities, it does not seem strange that you not seeing the changes that I (and others) do.

2) I don't understand this. Are you saying AC-3 content in AUTO mode is rendered the same as AC-3 content in STEREO mode?

Not quite. If you review my posts on this subject, you will note in most cases that I stated that AAC and AC3 1.0 mono audio under tvOS v9.0.1 is incorrectly rendered by the "Computers" app as stereo (PCM) in the TV4 "Auto" mode as if it were transformed using the TV4 "Stereo" mixdown mode as opposed to being correctly rendered (i.e., "played") automatically as a single active center channel with all other channels "empty" as under tvOS v9.0 (to which I have not yet found a way to easily revert).

3) I still see the same behavior -- dialnorm is removed from AC-3 encoded files in DOLBY mode. Saying all audio data was wrong since I haven't tested all possible input formats.

As previously noted, AAC mono audio tracks are now being correctly rendered (i.e., "played") on my system using the AAC to DD5.1 transform currently applied by the TV4 in the "Dolby Surround" mode under tvOS v9.0.1 using the "Computers" app. This is what I asked someone else to confirm. As to AC3 mono, it's "passed through" on my system using the same settings and is being automatically decoded/played correctly (as originally encoded) by my AVR with display indicators performing normally—i.e., displaying the correct active channel(s) as originally encoded. Not sure what you're trying to say in your last sentence.

Basically, I'm an old man—set in his ways—who likes his audio to automatically play using the same channelization originally used when encoding. I don't really care how it is output by the TV4 as long as it is played back through the correct speakers by the AVR without having to apply additional processing to simulate or recover original channel playback. This is why I'm currently using the TV4 "Dolby Surround" mode in preference to the "Auto" mode with my particular AVR and video content. If your library does not contain such encodings, you are satisfied with playback as it is on your system, and/or you are not experiencing any "mode sticking" issues, then this post would probably have little or no significance for you.

I appreciate all the input on this topic John. Have you done any Apple Music tests using the TV4 Dolby Surround setting? I checked it on my system and it appears to be delivering 5.1 rather than 2 Channel Stereo as it should for most if not all music content. I guess this means when I listen to music, I'll need to switch to another Audio Mode. I really hope the Auto setting is corrected one day and we'll be able to rely on it to output the intended audio format regardless of which app we're using.

I appreciate all the input on this topic John. Have you done any Apple Music tests using the TV4 Dolby Surround setting? I checked it on my system and it appears to be delivering 5.1 rather than 2 Channel Stereo as it should for most if not all music content. I guess this means when I listen to music, I'll need to switch to another Audio Mode. I really hope the Auto setting is corrected one day and we'll be able to rely on it to output the intended audio format regardless of which app we're using.

Yes, I have. The question of whether or not there is a problem depends on your point of view. Yes, stereo non-AC3 audio (e.g., AAC, MP3, WAV, Apple Lossless, etc.) is being sent to your AVR using an HDMI DD5.1 bitstream connection by the TV4 "Dolby Surround" setting under the current tvOS v9.0.1 update. However, if you actually check speaker activity aurally (i.e., ignore the AVR graphic indicators), you should only be hearing audio through your left and right front speakers—assuming the source file is in stereo. (If your receiver is equipped with an LFE "Activity" indicator in addition to the LFE channel indicator, then it is usually very easy to tell the difference between a "real" DD5.1 encoded track being "passed through" and AAC sourced audio being sent over the DD5.1 bitstream connection.)

Basically, what is happening is that the TV4 is opening the DD5.1 bitstream connection with your AVR but should only be "impressing" the audio from your non-AC3 source audio track to the corresponding channels of the DD5.1 bitstream. For example, if the source track is an AAC 1.0 audio track, active audio will only be "impressed" on the center channel of the DD5.1 bitstream along with 5 "empty" channels and plays back through your center channel speaker even though your receiver shows 6 channels being decoded. I.e., your receiver does not really distinguish between "active" and "empty" channel content—only that it's decoding a 6-channel stream.

This works the same way for video files. If the source audio track is AAC 1.0, 2.0, stereo, or Dolby Pro Logic II, then the source audio will be sent to your AVR as appropriate for the mono or L/R track source. On the other hand, if the source track is encoded as AC3 data, then the AC3 stream is passed directly to the AVR for decoding. In this case, the receiver correctly decodes, plays, and indicates which channels were originally encoded. In addition, if your receiver has a combined "Auto Surround + Dolby" control setting, it will automatically perform post processing of DD PL II content. Unfortunately, my receiver has separate controls for this, so I have to manually activate DD PL II processing if desired.

This is the same convention originally used for the "Auto" mode under the tvOS v9.0 release. The only real difference was that the TV4 established a DD+7.1 bitstream connection in the "Auto" mode but uses the DD5.1 bitstream connection in the "Dolby Surround" mode. Unfortunately, some users complained about the DD+7.1 bitstream setting off the DD Digital decoding indicator when listening to their music and the automatic invocation of undesired DD PL II processing on some receivers. As a result, Apple decided to switch to what appears to be the TV4 "Stereo" mode connection with receivers to pass 1.0, 2.0, stereo, and DD PL II track data using the "Auto" setting under the tvOS v9.0.1 update and, thus, avoids triggering AC3 decoding even though it should have produced the stereo front channel L/R playback without DD PL II processing if users simply turned off this post processing option. Unfortunately, this output setting transforms both AAC and AC3 1.0 center channel content into two mono channels (mono/mono) output making the "Auto" setting useless for the automatic playback AAC 1.0 and AC3 1.0 encoded content in the "Auto" mode. (I.e., to recover/simulate my original 1.0 center encode in "Auto" I now have to manually activate DD PL II processing.)

Personally, I would prefer reverting tvOS v9.0 if I could and am hoping Apple will not decide to "update" the current "Dolby Surround" output setting to mirror current "Auto" mode functionality. I.e., I can easily live with false AVR channelization indicators as long as the audio content actually plays back automatically as I originally encoded it.

In my short experience of the Apple TV 4th gen, it seems to be app specific as to whether it outputs 5.1. I use the "Infuse" app to view my mkv files and it outputs 5.1 correctly, however Netflix will not output 5.1 no matter what I try and there are no options in the settings for a 5.1 audio track like there is in the Infuse app.

All my sources are connected by HDMI to my receiver, and the fact that it works correctly in Infuse points to it being app specific. I will try a movie from iTunes tonight to see if that works as it should.

I To have no 7.1 output from Gen 4 Apple TV. Only 5.1 from iTunes and 2.0 Netflix .. Hope they can fix this soon . I just completed a 45 min call with tech support. They could not help. 7.1 on gen 4 was the only reason I made this upgrade from gen3 to gen4. Any input would be greatly appreciated