ATV 4K Audio settings

Discussion in 'Apple TV and Home Theater' started by oskarbar, Feb 23, 2018.

  1. oskarbar macrumors newbie

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    Feb 21, 2018
    #1
    Hi, I've the ATV 4K wired to my Samsung UE55JU6400 TV (which is 4K and theoritecally non-HDR, but plays HDR content; this is another history), and from the TV via HDMI ARC channel, wired to a 5.1 setup (Samsung MS-650 with subwoofer and rear speakers, I love this setup)

    The question is; in the ATV Audio settings I can choose between "Best Quality" or "5.1 output". Should I directly go with the 5.1 option, or let the default option of Best Quality (which in my case seems nonsense)?

    Regards!
     
  2. protobiont macrumors 6502a

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    #2
    So, I am no expert. But I have a similar set up and I’ve done a lot of reading. Hopefully someone can correct me if I am wrong.

    I’m pretty sure you should choose the 5.1 output option. From all I’ve read, the “best quality” option sends an uncompressed pcm signal, and no current TV will pass that through over ARC, so you only end up with a 2.1 pcm signal.
     
  3. oskarbar thread starter macrumors newbie

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    #3
    Ok, this is an interesting discussion.

    What I've read regarding how the audio is being transported through the HDMI, is that you usually can select Bitstream or PCM. In the Bitstream option the TV does not process the audio and sends the information bit by bit; in this case audio will be processed by the AV receiver (by your 5.1 system). In the second case, the TV does all the processing and directly sends the audio for each channel in PCM format. This is my understanding (please correct if wrong). I've tested with both settings in my TV and actually didn't notice any difference. I can hear 5.1 audio in both cases.

    Now, returning to the ATV settings.. Does "Best Quality" means Bitstream (audio not processed by ATV), and 5.1 means PCM DD5.1 (audio processed and splitted into channels by ATV)??

    Good question
     
  4. priitv8 macrumors 68030

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    #4
  5. oskarbar thread starter macrumors newbie

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    #5
    Thanks for the link, but i find this article outdated. In tvOS 11.2.6, at least in my unit, I can choose between "Best Quality" and "5.1 output". There is not an Auto mode, or stereo...

    Regards,
     
  6. JeffPerrin macrumors regular

    JeffPerrin

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    #6
    "Best quality" is what you want. Unless it doesn't work, then go with "Dolby 5.1" output, which is meant to be used with older receivers or set-ups incompatible with the first option.
     
  7. oskarbar thread starter macrumors newbie

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    #7
    Ok, so i understand that “best quality” is the old “auto” option. I’ll leave this in the default..

    Thanks!
     
  8. protobiont macrumors 6502a

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    #8
    Since you are using ARC from the tv to the receiver, I think you’ll find that your tv will send a 2.1 stream to your receiver if you select that option. Your receiver will then take that stream and upmix it to multi channel audio using Dolby prologic or one of the dts settings, but it won’t sound as good as a Dolby 5.1 stream.

    See here: https://www.rtings.com/tv/tests/inputs/5-1-surround-audio-passthrough

    Relevant text:

    PCM

    PCM is an uncompressed audio format, which means it will theoretically have the best overall sound quality, as no information has been removed to facilitate transmitting the signal. PCM is sent unencoded by the source, meaning the full, unpacked ‘instructions’ for what sounds to play are sent directly from the source to receiver, and then on to the speakers.

    Unfortunately, this makes for a signal that is more difficult to transmit. No TV seems to be able to pass a 5.1 PCM signal through to a sound system, so sending a PCM signal to or from a TV will downgrade the signal to 2.1 (two speakers + one subwoofer), thus eliminating the extra channels necessary for surround sound.

    PCM 5.1 can work with a receiver that supports the format, so if you want uncompressed sound, you’ll need to forego passing the audio through your TV, and instead output the sound directly from the source (one that outputs PCM 5.1) to the receiver. Note that only HDMI can transmit a 5.1 PCM signal. Digital optical is only capable of transmitting a 2.1 or 2.0 PCM signal.

    When to use PCM

    For 5.1 audio, use PCM sound only if you

    Output audio directly from each source device and to the receiver.
    Output this audio via HDMI, and not optical.
     
  9. oskarbar, Feb 24, 2018
    Last edited: Feb 24, 2018

    oskarbar thread starter macrumors newbie

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    Feb 21, 2018
    #9
    Thanks for the link!

    I’ve read the entire article and the configuration on the Samsung TV they recommend is exactly what I had enabled:

    With this config, as wrote in previous post, I understand that the TV does not process the audio and sends the info bit by bit to the receiver. Whether this is possible via ARC, is my only doubt.
     
  10. priitv8 macrumors 68030

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    #10
    This now comes down to the capabilities of each individual TV (ie passthrough of different formats into ARC). My 2016 Sony Bravia has no trouble with multichannel PCM of up to 6 channels and 24/192 resolution.
     
  11. scouser75 macrumors 6502a

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    #11
    Can I throw a slight curve ball in here please - I've just bought the Apple TV 4K, but am running it on a Philips 1080P set.

    I've connected the ATV to my Onkyo receiver. If I set the ATV to Best Quality, on my Onkyo what would be the best output mode on the Onkyo? Multi Channel Through? Multi Channel THX Cinema? There is a multitude of options!
     
  12. priitv8 macrumors 68030

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    #12
    Try them out yourself. Although to my ears THX Cinema sounds like a digital post-processing and I generally do not find them useful.
     
  13. scouser75 macrumors 6502a

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    #13
    May I ask what you use?
     
  14. priitv8 macrumors 68030

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    #14
    Sure! My receiver has a feature called "Auto Format Decoding" and I tend to use this. It reproduces 2.0 channel input as stereo and multichannel according to incoming signal format - PCM, Dolby or DTS with whatever channel count it receives, from 2.0 up to 5.1.2.
    I do not use any of the post-processed DSP functions, like the ones that create ambience (Stadium / Church / Concert Hall etc). I also do not normally use the pseudo-surround modes (that attempt to create surround sound from stereo input), like the Neo:6 or Virtual:X and the like.
    The less processing, the better.
     
  15. protobiont macrumors 6502a

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    #15
    Perhaps I’m missing something then, as my 2017 Sony only sends a 2.1 PCM signal over ARC. I only get 5.1 when I select Dolby digital. It could also be my older (8 year old) receiver??
     
  16. priitv8 macrumors 68030

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    #16
    I need to stand corrected. Because ARC is functionally equivalent to the S/PDIF optical link, it only can send compressed 5.1 audio (Dolby Digital or DTS). Only 2 channels of uncompressed (like PCM) audio are supported. And that is not a limitation of the medium, but intentional due to missing copy protection on the link.
    Source:
    https://www.tomsguide.com/us/hdmi-arc-faq,news-26262.html
    https://www.hdmi.org/manufacturer/hdmi_1_4/hdmi_1_4_faq.aspx#15

    My bad, sorry!
     
  17. protobiont macrumors 6502a

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    #17
    No worries. At least you chimed back in and saved me from several more hours trying to figure out which settings would give me better sound!

    Now if Apple will ever enable Atmos, I’ll look into upgrading the receiver.
     
  18. Menel macrumors 603

    Menel

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    #18
    Can you not goto sound system first? That is usually best.

    Like I have:
    ATV > Denon receiver > TV. ARC is only used for rare smartTV uses like before PrimeVideo was on ATV

    Or in my garage:
    ATV > yamaha soundbar > TV
     
  19. protobiont macrumors 6502a

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    #19
    Many older receivers don’t pass through 4K HDR video.
     
  20. Menel macrumors 603

    Menel

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    #20
    Time to upgrade
    Even the refurb cheapo soundbar I pickd up for garage does 2.2 hdr passthrough.
     
  21. phrekaru macrumors member

    phrekaru

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    #21
    Which configuration is the best? All conected by HDMI.
    1. Apple TV 4K - TV - Soundbar
    2. Apple TV 4K - Soundbar - TV
    My soundbar is LG SJ8 and the TV is a little bit older but its UHD.

    Thankz.
     
  22. scouser75 macrumors 6502a

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    #22
    Ok. These are the options I have in my Onkyo receiver for Apple TV. What would be the closest to unprocessed audio?

    Multi Channel THX cinema
    MC TV logic
    MC All channel stereo
    MC full mono
    MC theatre dimensional
    MC mono
    MC direct
     
  23. priitv8 macrumors 68030

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    #23
    According to Pg 48 http://www.uk.onkyo.com/downloads/2/2/4/0/7/Manual_TX-NR5010_TX-NR3010_En_web.pdf
    they are all DSP modes.
    I would normally select Multichannel (Pg 49) and set aTV to "Best audio" thereby leaving surround decoding to tvOS and letting AVR simply amplify the individual channel signals. That applies to default playback.
    If you are using 3rd party playback app that can pass through surround stream to HDMI out, then I would assume, your AVR is clever enough to decode it as needed.
     
  24. scouser75 macrumors 6502a

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    #24
    Thanks yet again pritv8 for your informed help.

    So, if I selected Multichannel direct, would that be what you mentioned above? I don't get an option for just Multichannel.
     
  25. priitv8 macrumors 68030

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    #25
    Sorry, I would be only guessing here, because I never had a Onkyo receiver. So I can not speak from personal experience.
    You can download a channel test file from Dolby: https://www.dolby.com/us/en/guide/test-tones.html
    and play it back from iTunes library to aTV and see how it is reproduced.
    They have Atmos sound in Dolby Digital Plus 5.1 encoding, hence play back as PCM Multichannel 5.1 on aTV.
    DD+ 7.1 channel check you can find here: https://www.demolandia.net/downloads.php?id=27781967
    But because it's in MKV container, you need to use eg Subler to remux it into mp4 for iTunes compatibility.
     

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