ATV3, Video/Sound Format, and 5.1 Surround Sound

Discussion in 'Apple TV and Home Theater' started by Benjer, Dec 27, 2017.

  1. Benjer macrumors member

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    #1
    With a few days off, I started messing around with the surround sound in our living room, as we have in-ceiling speakers that were installed by the previous owner. I hadn't done much with it besides a quick initial setup when we moved in.

    I have an older Sony audio receiver with just the option for 2-channel or optical in, so my ATV3 setup is HDMI from the ATV3 to the television, then optical audio from the television to the audio receiver. I was pretty sure 5.1 sound was working well based on movie playback, but I wanted to be sure, so I found a Dolby .mp4 video file to test the sound, imported it into iTunes on my computer, and streamed it to the Apple TV. When the video was supposed to play on the back (surround right and left) speakers, it never played just in either of the speakers when it was supposed to. But I knew the speakers were wired correctly because the receiver can produce its test tones correctly in each speaker.

    Finally after some searching, I found Home Theater Speaker Check for iOS, fired it up on the ATV3 via Airplay, and the speakers performed as expected.

    So of course I'm happy that I'm getting 5.1 sound through the AppleTV3 (at least where supported by Apple, such as movies rented from Apple). So technically, problem solved, and I should just move on with my life. But my curiosity needed to know why the videos—provided by Dolby's website—wouldn't play the 5.1 sound correctly. It seemed almost like the stereo was taking 2-channel sound and making it work for the 5.1 system, but the receiver indicates that it's receiving a Dolby Digital 5.1 signal from the Apple TV during the Dolby test video. (When I played a video via the ATV3's YouTube app, it indicated it only was receiving a stereo signal, so I think I can trust the receiver to be correct about what kind of signal it is receiving.)

    Since the speakers all performed as expected when tested using the Home Theater Speaker Check app, I think it has to be an issue with the actual videos, though there is no way for me to know for sure. The main test video I was using had "Dolby Digital Plus" audio. I read somewhere that for AppleTV to stream 5.1 sound from iTunes on a Mac using home sharing, it had to be AC3, so I used Handbrake to create a new file with AC3 5.1 sound, with the same result. Here's the QuickTime inspector for each file showing the audio information:
    Screen Shot 2017-12-27 at 9.39.51 PM.png
    And the one I converted to AC3 audio via Handbrake:
    Screen Shot 2017-12-27 at 9.40.44 PM.png


    So finally, to my question: what type of audio does a video need to have to utilize 5.1 sound on an AppleTV 3rd generation? And where can I get a test video that actually uses that audio, since YouTube on an AT3 does not support anything beyond two-channel sound?
     
  2. benji888, Dec 27, 2017
    Last edited: Dec 27, 2017

    benji888 macrumors 68000

    benji888

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    #2
    Rather than convert the file to iTunes why not just open it with QuickTime and AirPlay it from there? See if you get the same results.

    I’m not familiar with the app you mention.

    I also would recommend connecting an optical audio cable directly from your ATV to your AVR if you have another input, you may get better results, as TVs can sometimes have limitations, (some are limited to 16bit audio). Alternatively, if your TV has an audio pass-thru setting, I’d turn that on.
    --- Post Merged, Dec 27, 2017 ---
    Also, converting to AC3 will take DD+ down to DD. DD+ is a better codec. (DD+ is also called E-AC-3 or EC-3). You can see the results with the smaller data size & rate.
    Scratch that, ATV3 doesn’t handle DD+, (ATV 4th gen & later do).
     
  3. JeffPerrin macrumors 6502

    JeffPerrin

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    #3
    Hi Benjer, Jeff Perrin here, author of Home Theater Speaker Check.

    You are correct that the Apple TV 3 does not support E-AC3 (Dolby Digital Plus), only AC3 (Dolby Digital).

    Also, note the Apple TV can be pretty finicky on what sort of 5.1 you try to send it via Airplay. It's been a while since I tested the ATV3, but I recall support is hit-and-miss, depending on the device OS, ATV version, and exactly how the file was encoded.

    Glad to hear my Speaker Check app is working out for you. The good news is that if the 5.1 test in the app is successful, you can pretty much rule out your hardware or system set-up as the problem. :)

    Cheers,

    Jeff
     
  4. benji888 macrumors 68000

    benji888

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    #4
    I started to write that AirPlay doesn’t support 5.1 audio at all, but, then tried it via my Mac (to my ATV4), with one iTunes movie I knew was DD5.1 and it worked...thanks for clarifying that it is inconsistent.
     
  5. Benjer thread starter macrumors member

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    #5
    Good idea...tried it, same result.

    I should have mentioned that everything I have tried, I also have tried while connecting the ATV3 directly to the receiver to make sure the TV was not the issue. I am reasonably sure the passthrough is working correctly.

    My intuition says that because everything else works, it's the audio codec on the video. So at this point, I just want to know why, so I can understand better. If it didn't come directly from Dolby, I wouldn't worry about it. I wish YouTube supported 5.1 on the ATV3 so that I could just use one of those videos...
     
  6. JeffPerrin macrumors 6502

    JeffPerrin

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    #6
    Just a guess, but I suspect that the file from Dolby was DD+, and that the conversion from Handbrake (so as to attempt force compatibility with ATV3) messed something up along the way...
     
  7. HobeSoundDarryl macrumors 604

    HobeSoundDarryl

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    #7
    If I'm reading the first post correctly, I heavily suspect it's your setup:
    • :apple:TV3 will play commercial video 5.1 DD just fine- no doubt about that at all.
    • your TV is likely only outputting unprotected 5.1 through that optical port.
    • the test output from the app is likely unprotected DD5.1, so that's probably the ONLY real 5.1 your receiver is receiving via optical.
    The commercial videos, etc that your are pumping through the TV and then out the TVs optical port are probably being downconverted to stereo (Prologic). Prologic is fake 5.1 but your receiver may be portraying it since it is faking 5.1 and using the various speakers. Lots of TV optical out jacks will only output stereo regardless of what is received via an HDMI connection. This is likely what is happening to you.

    Now you say the receiver shows it is "receiving" 5.1, so if you know that to be true (and that is different then just lighting up 5 speaker icons), then the above suspicions are off. But I bet the receiver is receiving downconverted stereo and then using the Prologic function to fake surround and, in doing so, lighting up the 5 speakers since Prologic is using those speakers. It's less customer service to just light up those icons than having to educate consumers that it's really fake 5.1 via Prologic.

    The format of the videos is almost certainly not where the problem lies. If it's there, everyone is going to have problems with them using :apple:TV and few are going to want to be converting videos to get the right sound format when it's already in a usable format. If it's the same test video I've used myself, I didn't have to make any changes to the file to yield 5.1 or 7.1 tests.

    3 potential solutions:
    1. Go into the audio menu of your TV and see if your optical out can be toggled from stereo to surround. This can have a variety of names so you may need to pop open the TV manual and find this particular option if yours is the relatively rare TV that will receive a video + 5.1 signal via HDMI and forward the 5.1 signal out via optical.
    2. Buy a HDMI in:HDMI (video) Optical (audio) splitter out device. The HDMI in would be a short cable from :apple:TV3 to this device. HDMI out would go to the TV using the existing HDMI cable already hooked up. Optical out would go to the receiver. This would very likely pump your 5.1 (real) surround sound to your receiver. Just be sure the device you choose for this specifically defines that it will split out 5.1 surround audio.
    3. Buy a new, much more modern receiver and hook up :apple:TV to receiver via HDMI, then HDMI out to TV via HDMI.
    #3 will almost certainly resolve your problem. #2 will be cheaper but it too will almost certainly resolve your problem, AND likely cost a fair amount less than buying a new receiver. #1 is long shot- odds are very high your TV does NOT replicate the function of #2 through it's optical out jack- almost no TVs do.

    If you have other HDMI components besides :apple:TV, #3 is the best option, as all sources will start using your speakers with real 5.1 surround. #2 is a single-component solution (unless you want to be switching cables when you use stuff other than :apple:TV).

    I hope this helps.
     
  8. Benjer thread starter macrumors member

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    #8
    I thought that might be the issue. I wish the ATV3 would just passthrough the signal, because I know that the receiver would handle it fine (Dolby says that Dolby Digital Plus is backward compatible with older receivers that can handle Dolby Digital signals).

    Thanks to your app, Jeff, I know for sure that at the very least 5.1 from the ATV3 is working. The thing I don't fully know is working is streaming to the ATV3 from the Mac. Again, this is just curiosity for me, because we don't own any digital movies that aren't iTunes or MoviesAnywhere, so we just play the movies right from the ATV3. So, I don't actually need to know it works, I just want to understand better. What puzzles me is that I can't seem to find rock solid documentation from Apple about when 5.1 sound is supported on the ATV3 and when it is not. I probably wouldn't have started down this rabbit hole if I didn't have a week off at home. :)
     
  9. HobeSoundDarryl macrumors 604

    HobeSoundDarryl

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    #9
    5.1 IS supported when the file has it as an audio track and your playback equipment (receiver) is connected such that the 5.1 can actually get into the receiver as 5.1. I don't think that is happening for you because you have your TV playing middleman. In short, I suspect :apple:TV3 is pushing 5.1 audio to the TV, the TV is (very likely) down-converting it to stereo, the optical cable is delivering it as stereo and your receiver is turning that stereo into Prologic (displaying it like it's surround sound, which it is- faux surround sound).

    And note: having posted both of the above, I just remembered that the :apple:TV already has an optical audio out jack built in. Cut the TV out of the (audio) chain and go :apple:TV optical audio out to receiver optical audio in. That should make everything play in 5.1 when the source is 5.1 (or 7.1).

    If not, check your settings in both the :apple:TV and the receiver to be sure both optical connections are setup for 5.1.

    I can also confirm 7.1 DD+ will play fine on a 5.1 setup. It IS backwards compatible.
     
  10. Benjer thread starter macrumors member

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    #10
    If I understand you correctly, you're saying that the TV is down mixing the 5.1 sound to stereo. I thought about that as well, but 1) I get the same results connecting the ATV3 optical out directly to the receiver, and 2) the TV optical out setting is set to surround sound. Again, that doesn't mean it doesn't correctly pass it through, but given that I get the same results whether the ATV3 audio is passed through the TV or it goes directly to the receiver, I doubt it's the TV.

    When playing a video with Dolby sound, it doesn't just light up all 6 speakers, it also flashes a "DOLBY DIGITAL" message when the video starts.
     
  11. HobeSoundDarryl macrumors 604

    HobeSoundDarryl

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    #11
    No I do suspect it's the TV. Even if you can set it to surround out, I think commercial video sent to the TV protects both video & audio, and thus it's not giving the TV permission to receive 5.1 and push it out at 5.1

    However, given that you get the exact same result when you connect the :apple:TV3 directly to the receiver via optical, I now suspect you don't have your settings right on the :apple:TV and/or on the receiver. I don't remember the exact option on the :apple:TV3 but I think you can go into "Audio & Video" and the audio options- I think- are something like "best available", "dolby digital" and maybe a third (possibly) "stereo". Set it to "best available" if it's "stereo" or similar.

    I heavily doubt your receiver needs you to tell it to receive DD via optical but you might as well check it's audio settings for the port too. It's hard to think of a scenario where a receiver would require a specific setting rather than just auto-detect what kind of audio it is receiving but conceptually, there might be such a setting in your receiver.

    Even if it flashes DOLBY DIGITAL but you are not getting discrete sound from the rears when testing it with Dolby test videos, something is not set properly or your receiver must have some issue. It's very likely NOT going to be the format of the video files themselves. Else, lots of people would chime in with me-too gripes about the same problem.

    If you want to identify the specific test video you used with a link, I'll test it on my own setup and confirm that the rears don't play their parts... or that they do. But before I even try, I'm already practically certain that they will indeed play it.
     
  12. Benjer thread starter macrumors member

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    #12
    Sorry I missed this reply before I posted mine. When the receiver converts stereo sound to Prologic, it flashed a "DOLBY PLII" message. When it's playing Dolby 5.1, it flashes a "DOLBY DIGITAL" message.

    I may just download some of our movies that we own right to the Mac and see if I can tell a difference. I do trust my ears, I would just rather have a true Dolby test video to know for sure.
    --- Post Merged, Dec 28, 2017 ---
    On the ATV3, I have Dolby Digital set to "on." And the receiver does not have a setting to specify DD, just what kind of signal it is expecting by default, and I have that set to "optical."

    I got the test video from the Dolby site here. When you go to the Mac tab, it has you download an app that will download the "right" files. Kind of weird. But the 5.1 files it downloads are the same ones you can download directly from the Windows tab.
     
  13. HobeSoundDarryl, Dec 28, 2017
    Last edited: Dec 28, 2017

    HobeSoundDarryl macrumors 604

    HobeSoundDarryl

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    #13
    OK, to try to help you narrow it down, I went to that very same Dolby link. I chose the first option "For Windows" 5.1.2 teal button. This opened the file in Quicktime on my Mac.

    I right clicked and chose "Download file" (to my desktop) because I wanted to cut the computer airplay variables out of the equation.

    Then I dragged it into iTunes unchanged- just as you can with any MP4 file.

    iTunes sees it as a "home movie" instead of a movie, so on my :apple:TV4, I had to go into the "home movie" section to play the file. I can't remember if it shows that way on :apple:TV3. If not, it will probably just land in your movies list.

    That video (slowly) cycles through the speakers visualized in the on-screen setup: front speakers... then left & right rears. I can confirm on my setup which is HDMI from :apple:TV into my receiver, it does play sound from each speaker, matching what shows on screen. Since your problem is rears, I verified that I could fast forward to the point where the rears are playing and then it played discrete sound from each in sync with which speaker was highlighted on screen.

    Now, before you shared the link, I hopped onto youtube and it will present a ton of Dolby Digital test videos. I tried a few and they all showed as "DOLBY DIGITAL" with the all the speaker icons lit up but they were not playing discrete sound from the rear speakers when they implied they should. So I still suspect your receiver is receiving stereo, maybe DOLBY DIGITAL is lighting up because it may be DOLBY DIGITAL 2.0. I know on mine, every one of the youtube DD videos I tested both showed themselves as DOLBY DIGITAL and lit up ALL of the speakers (but would not play discrete sound form the rear speakers).

    So, try the above (cutting your computer out of the equation). Drag it into iTunes and then play it like any other home movie on your :apple:TV. Did you hear discrete sound from the rears when it was showing sound should be coming from the rears?
     
  14. Benjer thread starter macrumors member

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    #14
    I have read elsewhere that only ATV4 and 4K support Dolby Digital Plus (not ATV3 and older) and those files are DD+. I think that when you stream I wonder if that's the difference?

    As far as I can tell, the YouTube app only supports stereo on the ATV.

    This is what I did...and I did not hear discrete sound. Again, might that be because the ATV3 doesn't support DD+? (I would imagine that when you stream movies from the ATV right from Apple, it knows it's an ATV3 and Apple's servers sends a 5.1 signal rather than a DD+ signal.)

    Today, I'm going to stream the same movie right from my Mac as well as from Apple's servers and see if 5.1 works on both. If it does, I'm just going to call it good. The only reason I'm down this rabbit hole is curiosity, and if everything "works." :)
     
  15. HobeSoundDarryl, Dec 28, 2017
    Last edited: Dec 28, 2017

    HobeSoundDarryl macrumors 604

    HobeSoundDarryl

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    #15
    I no longer have an :apple:TV3 to test but I doubt it's a DD+ issue. As I recall it, DD+ is backwards compatible. Instead of discrete left & right in the rears, it just sends it to both surrounds at equal volume to simulate having dedicated rear speakers. I've long used a DD+ demo to test but I can't remember if I had that video when I had the "3".

    HOWEVER, I got that file from an archive that had dozens of DD demo files, not the DD site but somewhere else. I don't remember where but you might want to do some searches.

    Update:looked around and a LOT of sites lean on youtube files for their demo downloads, meaning lots of them end up as only 2-channel stereo in spite of what the video implies. However, this one has a VOB file download that does have DD5.1 in it (click the image that looks like a living room with 5.1 speaker setup to trigger the download). Running it through Handbrake with the :apple:TV3 preset should yield a :apple:TV file with 5.1 sound for testing.
     
  16. JeffPerrin macrumors 6502

    JeffPerrin

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    #16
    Right - ATV3 is unable to passthrough DD+. (Confirmed w/Dolby last year.)

    And forget about YouTube test videos - despite any (typically disingenuous) title claims, 5.1 is not supported; stereo only! (Though your receiver may fake the the surrounds with DSP) However, maybe that AC3 is now recently free of royalties, this will change in the near future?
     
  17. Benjer thread starter macrumors member

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    #17
    Update: Now I'm super confused. I watched a scene from a movie (Jason Bourne, if you're curious), first using the movie app on the ATV3 (so it was streaming right from Apple's servers), then streaming it from the Mac (I checked network activity on my mac using Activity Monitor to make sure the movie was indeed coming from the Mac, which it was), and I thought the 5.1 sound worked. At the very least, I know for sure the sounds coming from the front and rear speakers were distinct (gun fire that came only from the rear, murmuring in a control room that was only in the rear, while other action sounds were coming only from the front at the same time etc.). I played the scene a few times with each setup. I was satisfied that it wasn't upmixing a stereo signal, because there's a pretty clear difference between sound ONLY coming from the rear and upmixing, in which I can hear the same sounds always coming from the front and the rear at the same time. At least I think my ears are that good, but I'm now doubting myself, because...

    ...when I opened the Jason Bourne file in QuickTime and checked the inspector, the sound format is reported as MPEG-4 AAC, 480000 Hz, Stereo (L R). Clearly I didn't hear what I thought I heard and my ears aren't as good as I thought. But I'm also puzzled as to why an HD download doesn't have 5.1 sound attached to it. Might be because it's a Movies Anywhere movie, and iTunes will only give me a copy with stereo sound? But all of the other HD movie downloads from iTunes in my library have AAC stereo sound, not AC3 5.1.

    So, I'm now more confused than when I started and close to giving up on understanding. At the very least, I know the ATV3 and TV are set up correctly, and that the speakers work as expected using Home Theater Speaker Check. However, if I could get my hands on a 5.1 (just Dolby Digital, not DD+) test video that was compatible with Mac, I would at least know for sure.
     
  18. HobeSoundDarryl, Dec 28, 2017
    Last edited: Dec 28, 2017

    HobeSoundDarryl macrumors 604

    HobeSoundDarryl

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    #18
    Quicktime Inspector won't always show 5.1 channel. For example, a movie that I know for certain is 5.1 shows up just as you noticed in Quicktime inspector as stereo (L,R) with no hint at the 5.1 track that also is there. However, open the same movie in something like Subler and you will see both tracks are there.

    The old Quicktime had a more detailed window that would show individual tracks associated with a video like Subler does now but the new Quicktime simplified things. Some videos I've shot myself will show the 5.1 info in the (new) Quicktime Inspector window but commercial movies generally don't seem to show that even though the track is definitely there.

    The "Movies Anywhere" variable throws an unknown into the mix, so that video could have stripped the DD5.1 channel. For example, ALL of the streaming services for the "cord cutters" strip the 5.1 from the cable replacement TV they serve up.

    That link I offered in post #15 will get you a VOB that you can run thorough Handbrake and it will deliver a true DD5.1 test file you can drop into iTunes and stream it to :apple:TV. Incidentally, after running it through Handbrake to convert it from VOB to .m4v, Quicktime Inspector shows it's audio as only stereo L,R but both Handbrake and Subler show the 5.1 AC3 track is in there too.
     
  19. Benjer thread starter macrumors member

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    #19
    I totally missed that link! Ran it through Handbrake, popped it into iTunes, and it produced true 5.1 sound through the AppleTV3. Done and done. Thanks!
     
  20. HobeSoundDarryl, Dec 28, 2017
    Last edited: Dec 28, 2017

    HobeSoundDarryl macrumors 604

    HobeSoundDarryl

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    #20
    One more thing you could test. Try the optical out of your TV and see if that same video pipes real 5.1 back to your receiver. If so, you can go back to the setup at the start of this thread. If not, the longer term solution is probably replacing that receiver so that you can easily utilize multiple components capable of 5.1 without having to swap around cables.

    Note: there's actually 2 tests here- the unprotected demo and, if that yields 5.1 sound from the TV, try the (protected) video like the Bourne movie or something else where you are certain you have 5.1 video.
     
  21. priitv8 macrumors 68040

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    #21
    AppleTV has been able to play back DD5.1 (aka AC3) surround sound since it's very first incarnation (the silver mac-mini-like box).
    The movie file needs to provide both AAC-encoded stereo track (so-called fallback), plus a AC3-encoded 5.1. surround track.
    AAC track must be enabled, AC3 track must be disabled. Fallback link from AC3 to AAC should also be set.
    Both Handbrake and Subler can sort these things out as required by Apple specs.
    Requirements are documented in: https://developer.apple.com/library/content/technotes/tn2429/_index.html
     

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