AppleTV 4 surround sound issue

As I said, what seems a long time ago, only if your AVR is misleading you since it says DIAL NORM. Dialog Normalization isn't constant and it's independent of AVR settings unless your decoder is broken and presumably fails to meet Dolby certification. As previously noted mediainfo (available on most common platforms) will display dialnorm in an unencrypted disk file. I have values from -27dB to -31dB. By the way my AVR displays dialnorm -31dB differently from no dialnorm.

MediaInfo for audio tracks in a typical M4V iTunes managed library file:

Where am I supposed to find the Dialnorm info?

If you have Netflix check Jessica Jones episodes 1 and 2. Episode one has dialnorm -5dB and episode two has dialnorm -4dB on both my ATV3 and my TiVo. Both are reported as 0/missing via the ATV4gen (with Surround Dolby).

TV4 Netflix app:

Episode 1: plays as DD5.1 w/Dialnorm +4

Episode 2: plays as DD5.1 w/Dialnorm +4

TV3 Netflix app:

Episode 1: plays as DD5.1 w/Dialnorm -1

Episode 2: plays as DD5.1 does not cycle through Dialnorm display

Oppo Netflix app:

Episode 1: plays as user selectable Stereo PCM or DD+5.1 w/Dialnorm -1

Episode 2: plays as user selectable Stereo PCM or DD+5.1 but does not cycle through Dianlnorm display

Handbrake encoded files display "Dialnorm +4" on both TV3 and TV4 when playing the AC3 track in respective "Computers" apps using "Auto" mode for TV3 and "Dolby Surround" for TV4.

The GUI version of mediainfo only shows basic data. I normally use Linux for things like this but mediainfo is available via Homebrew. Given only the dialnorm display results you've shown it would appear that your AVR is not actually displaying dialnorm or it's faulty. Dialog normalization happens in the (E-)AC-3 decoder and a display of that value should just reflect the input parameter. By the way, dialnorm is not meta-data -- it changes the output.

$ for i in Dolby*;do echo $i;mediainfo -f $i|grep dialnorm;done
Dolby-City.m4v
dialnorm : -27
dialnorm/String : -27 dB
dialnorm_Average : -27
dialnorm_Average/String : -27 dB
dialnorm_Minimum : -27
dialnorm_Minimum/String : -27 dB
dialnorm_Maximum : -27
dialnorm_Maximum/String : -27 dB
dialnorm_Count : 32
Dolby-Egypt.m4v
dialnorm : -31
dialnorm/String : -31 dB
dialnorm_Average : -31
dialnorm_Average/String : -31 dB
dialnorm_Minimum : -31
dialnorm_Minimum/String : -31 dB
dialnorm_Maximum : -31
dialnorm_Maximum/String : -31 dB
dialnorm_Count : 32

By the way, dialnorm is not meta-data -- it changes the output.

Sorry! As explained in another discussion in which you participated, this is not my area of expertise. I merely used the term in reference to the phrase "meta data parameter" as per HAL9000's linked article. I tend to think of it as a "playback" or "rendering" instruction embedding in the source file—much like "current" playback dimensions or targeted aspect ratio settings which are independent of the compressed data actually stored in a file.

The GUI version of mediainfo only shows basic data. I normally use Linux for things like this but mediainfo is available via Homebrew.

Well, that explains that. Unfortunately, I currently don't have the time required to learn how to use/communicate with this version of the app at such a low level. While I might look into this further next year when/if I have the time, I rarely pay much attention to Dialnorm displays and am more concerned with proper channelization than comparative level standards that I probably can't accurately hear/differentiate aurally in any case at my age.

Given only the dialnorm display results you've shown it would appear that your AVR is not actually displaying dialnorm or it's faulty. Dialog normalization happens in the (E-)AC-3 decoder and a display of that value should just reflect the input parameter.

I'm leaning more towards what I consider a more simple explanation that both explains and correlates the differences we are seeing. I notice you say that a display of the dialog normalization value "should" just reflect the input parameter. What if we posit that my receiver displays the net adjusted input parameter plus my receiver's calibrated adjustment for speaker location/orientation and follow that logic:

1. As previously stated, my receiver was calibrated (for a somewhat strangely "landscape" shaped "Home Theater" viewing area having a wider than normal Left/Right speaker separation and a narrower than normal Front/Rear speaker separation). As a result, it appears to have a "+ 4" dialog normalization adjustment programmed into the system.
2. As previously indicated, all (but one) of my iTunes managed video library files were encoded by me with a zero gain level target. However, since I have no way to examine these files other than your suggested workflow (which I am reluctant to try without a lot more information), I can't even determine if my files contain a valid dialog normalization setting—let alone a valid 0 db equivalent (which is, at best, only an assumption at this point). In either case, let's see what happens if we continue under the assumption that the dialog normalization is either 0 db or missing...
3. In the case of my TV2 and TV3 test, my encoded files display an adjusted value of "0" plus my "+4" adjustment or a net "+4" adjusted value which I do see and have previously reported.
4. In the case of your Jessica Jones episode 1 file, you see a dialog normalization value of "-5 db" while I see "-1" which is the net adjusted value for a "-5db" input value plus my receiver's "+4" adjustment when both of use a TV3 device for playback.
5. In the case of your Jessica Jones episode 2 file play through TV3 devices, you see a dialog normalization value of "-4 db" while I get no dialog normalization display for the adjusted "-4 db" plus my "+4" receiver adjustment which provides a "0" net adjusted value which you (and others) have indicated can produce inconsistent value displays by various receiver brands and models.
6. On the other hand, both Jessica Jones episodes on the TV4 produce "0/missing" readings on your system but return a "0/mising" plus my "+4" adjustment or "+4" net adjusted display on my system.
7. Your TiVO and my Oppo Netflix app alternatives both produce the same consistency in results as paragraph 3 and 4 above.

In any case, applying Occam's Razor, this hypothesis seems to currently be the simplest, and thus, preferred explanation until something better comes along. Was however, wondering if you could/would download and examine a couple of test files already posted to determine if they contain valid or 0/missing dialog normalization values:

http://downloads.walker4.me/Temporary_files/Test-1.m4v

http://downloads.walker4.me/Temporary_files/Test-2.m4v

http://downloads.walker4.me/Temporary_files/Test-3.m4v

Your test files all have a dialnorm of -31dB. If your AVR does display something other than dialog normalization despite the label then I hope it has an option that you activated that enables that "feature".

Sorry - I'm not sure what you guys have been debating for the past 10 posts or so... but, can someone tell me if what I'm doing is right?

Content: iTunes Downloaded TV Show (The Wire) also Netflix (Greece, Days of Thunder)

ATV4: Set to Auto - Sound outputs at all 5 speakers. Amp displays Linear PCM [3/4.1] 48kHz. Sound does not come out of Subwoofer.

ATV4: Set to Surround - Sound outputs at all 5 speakers. Amp displays Dolby Digital [3/2.1]. Sound does not come out of Subwoofer.

Content: iTunes Downloaded Music (Florence and the Machine)

ATV4: Set to Auto - Sound outputs at Front L/R speakers, but plays through subwoofer as well. Amp displays Linear PCM [2/0] 48kHz.

ATV4: Set to Surround - Sound outputs at Front L/R speakers, no subwoofer. Amp displays Dolby Digital [3/2.1]

Receiver is a SONY STR-DN1040. Everything is connected via HDMI. HDMI from ATV to Receiver. HDMI from receiver to TV. Receiver acts as HDMI hub.

Receiver is set for AFD Auto.

Receiver is a 7.2 receiver, but I only have it hooked up at 5.2. The receiver configuration also is set for 5.2 only.

So - by leaving it set at Auto, it seems to be working successfully. Except that I can't get the subwoofer to play during any video output on the ATV.

(the subwoofer works properly when connected to broadcast TV, DVD, Bluray, and test tones).

What am I doing wrong?

bkafrick wrote:

Sorry - I'm not sure what you guys have been debating for the past 10 posts or so... but, can someone tell me if what I'm doing is right?

It might be better to start a new thread but a minimal function test is to get the Theater Test app, set Surround Sound to Auto and test each channel. If that doesn't show correct channel assignment you have a configuration error. Apple really should have an audio test in the Calibrate section but they don't (yet).

bodosom wrote:

It might be better to start a new thread but a minimal function test is to get the Theater Test app, set Surround Sound to Auto and test each channel. If that doesn't show correct channel assignment you have a configuration error. Apple really should have an audio test in the Calibrate section but they don't (yet).

OK - excellent suggestion. Thanks!

Downloaded it and paid my $1.99, and all channels are working properly when set to Surround = Auto.

Is it possible that no video content from iTunes or Netflix has any LFE signals? That just seems... strange.

bkafrick wrote:

Is it possible that no video content from iTunes or Netflix has any LFE signals? That just seems... strange.

The Netflix test video (Example Short 23.976) has an LFE sweep starting at about the 10 minute mark.

bodosom wrote:

The Netflix test video (Example Short 23.976) has an LFE sweep starting at about the 10 minute mark.

Well, that worked just fine.

I guess my setup is working properly. It must just be the content i've chosen. Strange.

Thanks for the help.

Your test files all have a dialnorm of -31dB. If your AVR does display something other than dialog normalization despite the label then I hope it has an option that you activated that enables that "feature".

First of all, thank you for taking the time and effort to examine the files.

As to my dialog normalization display, it appears to refer to the net adjustment applied to content after combining the source content parameter setting with the final "tuned" calibration setting in most cases. I.e., after the system was balanced and "zeroized," the calibration program for my system allowed the user to apply an offset to "tune" playback to individual taste if desired. This was not a labeled preset or "switch" to be activated like No or None, Action Movie, SitCom, Sports, Jazz, Rock, News, or similar targeted adjustments. I suspect the only way to readjust the this setting would be to rerun the entire calibration program and simply opt out of the process once the system was balanced and zeroized but before "tuning" playback to individual preferences.

With regard to your "-31 db" dialog normalization value, if this, as HAL9000.2 seemed to imply, equates to a "zero" or "no gain reduction" setting, then, by design or by accident, my AC3 tracks were encoded exactly as I intended—i.e., zeroized. Further, if your "-31 db" reference is represented on my system as a "zero index" reference (which never displays on my AVR), then the "+4" represents an "out or range" display equivalent of a dialog normalization parameter of "-27 db"—which I am given to understand is a common "Action Movie" setting that provides both natural playback of dialogue in motion picture soundtracks and plenty of headroom for concussive explosions that rattle a viewer's chest cavity but, at reasonable master volume levels, does not shake walls or prompt neighbors to come running. Based on my system's display of third-party content and comparisons with the data you and others previously provided, it appears my display is offset by "+4" over the "legal" range of values, displays nothing for a "zero" (e.g., -4 db source adjusted by +4) index, and displays "plus" values for "adjusted" values that are not in the AVR's programmed "legal" range of values (e.g., -1 db source adjusted by +4 yields a "+3" display). This receiver is somewhat old and I don't know if such display is typical for newer or "high end" units and my use of AC3 audio only began in earnest after Apple added AC3 transport stream support to the TV device.

Again, thank you for taking the time to try and explain dialog normalization. While my workflow may not be typical and I an unconcerned with being able to create a "standardized" Home Theater experience for comparison purposes with other Home Theater environments, I was curious as to its purpose and function. Now that I see this issue is unrelated to the question of transport stream playback of program stream stored AC3 and non-AC3 compressed data, I can, with an easy heart, return to the routine processing of library files.

I've been following this thread and I'm glad some of you seem to have gotten your ATV 4 to work correctly with Dolby Digital content. My ATV 3 worked perfectly with all my local content via Home Sharing, but with the ATV 4 in the forced Dolby Digital surround mode it will show as Dolby Digital on the AV Receiver with all 5.1 channels but only play out of 2 Channels. I've tested the files Jon provided and the Battleship one does work with the surround channels but other content doesn't. As pointed out earlier in this thread, that it seem the ATV 4 is not sending the signals for the AVR to interpret correctly for all the channels to be used.

I've sent my feedback to Apple as well, as this is a step back for me compared to the ATV 3. Seems like such a simple concept.

propellerhead00 wrote:

I've been following this thread and I'm glad some of you seem to have gotten your ATV 4 to work correctly with Dolby Digital content. My ATV 3 worked perfectly with all my local content via Home Sharing, but with the ATV 4 in the forced Dolby Digital surround mode it will show as Dolby Digital on the AV Receiver with all 5.1 channels but only play out of 2 Channels. I've tested the files Jon provided and the Battleship one does work with the surround channels but other content doesn't. As pointed out earlier in this thread, that it seem the ATV 4 is not sending the signals for the AVR to interpret correctly for all the channels to be used.

I've sent my feedback to Apple as well, as this is a step back for me compared to the ATV 3. Seems like such a simple concept.

What I realized while troubleshooting this "issue" was that you don't have to set the ATV4 in forced Dolby Digital. Setting it to auto DOES work, it just won't say Dolby Digital on your AV Receiver. It'll still come through in 7.1 PCM, and will play properly through all your channels. I was used to PCM being 2 Channel, but my receiver specifically says "PCM [3/4.1]" which is proper for full surround sound.

Check out my post above, and some of the troubleshooting that bodosom helped me with.

My ATV 3 worked perfectly with all my local content via Home Sharing, but with the ATV 4 in the forced Dolby Digital surround mode it will show as Dolby Digital on the AV Receiver with all 5.1 channels but only play out of 2 Channels.

This may be normal. Do your files contain just AAC audio or AAC and AC3 audio tracks with the AAC track enabled and the AC3 track disabled? If so, that may be what is causing your problem. The TV3 device can automatically select the AC3 track if available whether it is enabled or not. However, the TV4 selects the first enabled track whether it is AAC or AC3. Since the AAC track normally contains 1.0 mono, 2.0 mono, or 2.0 stereo audio, the TV4 Dolby 5.1 connection with your receiver only sends one or two channels of audio over the connection. You can think of this like having six audio cables connecting your TV4 to your AVR but only using one or two of them to actually carry audio.

I've tested the files Jon provided and the Battleship one does work with the surround channels but other content doesn't.

The Battleship segment (Test-3) is the only one encoded as AC3 5.1 audio. Test-1 (King Kong-1933) is an AC3 1.0 mono encode and Test-2 (Mission Impossible Rogue Nation trailer) is an AC3 2.0 stereo encode. Each file is set to auto-select the AC3 track upon initial opening but also contains an AAC 1.0 or 2.0 audio track which can be alternatively played for comparison purposes. Since I have no way to encode DD+7.1 content anyway, I use the "Dolby Surround" mode to play my AC3 tracks because it allows my decoder to accurately decode and display my content as the channels were originally encoded—i.e., a center channel AC3 track displays as mono content playing through the center channel, stereo shows up as L/R stereo, active DD PL II content shows activity on the originally encoded channels, and DD5.1 audio lights up all 6 DD5.1 lights with the LFE indicator active when processing data. While playback of non-AC3 audio in this mode will falsely display mono or stereo content as DD5.1 audio, the lack of LFE activity easily reveals the false display. The "Auto" mode has a similar problem with 5.1 content which displays 7.1 content but only plays 6 channels of actual audio.

As pointed out earlier in this thread, that it seem the ATV 4 is not sending the signals for the AVR to interpret correctly for all the channels to be used.

In "forced" multichannel operation the TV4 only tells the AVR how many channels are available to carry audio—not which channels are in actual use and which are empty. If the source audio is properly channelized, then the output should also be properly channelized.

propellerhead00 wrote:

I've been following this thread and I'm glad some of you seem to have gotten your ATV 4 to work correctly with Dolby Digital content.

Well strictly speaking I think you can make the argument that it's not completely correct. My point was always that Surround-Dolby is re-encoding the data. Since (E-)AC-3 is a lossy process it's not possible that the re-encoded output from the ATV4gen is the same as the input and the output from the AVR decoder will be yet further from the source. The "better" solution is to use Surround-Auto which results in a single decode, but ... if you have AC-3 dependent processing based on the number of advertised channels that gets broken. So you have to pick the lesser of two evils. I suppose it's convenient that Apple is doing the dialog normalization otherwise some people might wonder what is going on with the ATV4gen in "pass-through" mode.

There is definitely another problem which is probably what you're seeing. The ATV4gen plays the first audio stream by default and that may be AAC 2/.0. You can select the AC-3 audio track (probably the second English track if the first is a stereo mix-down) or as noted somewhere use a utility like Subler which can "correctly" (i.e. per Apple) flag the AC-3 track as the default.

Some people think there are gain management issues with Surround-Auto so that could be a problem too but not one that produces 2/.0 mix-down from 3/2/.1 content.

Don't get hung up about seeing a PCM signal on your receiver Its partly to do with where the signal is converted. Ultimately everything is converted to PCM. If your AVR is receiving a 5.1 PCM signal then thats what it will broadcast. If it receives a 7.1 PCM signal then thats what it will broadcast. DTS is simply encoding PCM to bitstream format thus compresses the signal received and is lossy. As far as I am aware PCM is a lossless format. Dolby Digital TrueHD, and DTS-HD Master Audio are lossless versions of DTS which ultimately convert back to PCM.