ATV4 audio quality

Discussion in 'Apple TV and Home Theater' started by Jackintosh, Nov 6, 2016.

  1. Jackintosh, Nov 6, 2016
    Last edited: Nov 6, 2016

    Jackintosh macrumors 6502a

    Jackintosh

    Joined:
    Mar 21, 2009
    Location:
    Illinois
    #1
    With optical audio output missing in the ATV4, I noticed audio quality not quite as good as ATV3's direct optical output to my stereo receiver. Especially true when listening to iTunes music. Now have optical input coming from the TV where ATV4 is connected.

    Tweaking some of the ATV4 audio settings seems to have brought it back to about the same level as ATV3. This included surround sound set to stereo instead of auto, turning off sound effects, set audio mode to 16 bit, and turning Siri off.

    Some of this may not have done anything, but I wanted to remove as much ATV interference as possible in keeping the audio signal unaffected. Anyone else notice this or try any audio tweaking? Granted, my system is not surround sound but only stereo.
     
  2. HDFan macrumors 6502

    Joined:
    Jun 30, 2007
    #2
    You didn't mention what your audio source is. Movies (SD, HD?), CD's, high res audio files, iTunes, Netflix? Some the codecs are the same on the ATV4 so you shouldn't hear anything different.

    According to the Apple specs ATV4 supports Dolby Digital 5.1 and Dolby Digital Plus (EC-3) 7.1 where the ATV3 only supported Dolby Digital 5.1 surround sound pass-through. Apple specs don't list the data rates supported.

    I find discussions of total available bandwidth available with specific codecs very confusing. For example Wikipedia says:
    EC-3 supports 15 "full bandwidth channels at a maximum bitrate of 6.144 Mbps" (Wikipedia). Unfortunately "full bandwidth" isn't defined.

    You will also find comments about Dolby Digital saying:

    Dolby digital supports 5 channels of 640 kbs which comes out to a maximum of 3.2 Mbps for all 5 channels. Delivered capacities would be less due to the restricted frequency range of some channels, such as the subwoofer.

    However if you check with Dolby:

    http://www.dolby.com/us/en/technologies/dolby-digital-plus-audio-coding-tech-paper.pdf

    they say that the maximum EC-3 for blu-ray 5.1 is 1.7 Mbps and the Dolby Digital maximum for DVD is 448 kbps. Maybe the 640 kbps is the maximum bitrate for all channels combined?

    Bottom line: EC-3 has a greater maximum capacity than DD5.1.

    The question then becomes the output capacity of the ports. This is just as confusing. Toslink (optical) according to Wikipedia does not have the capacity to support DTS-MA (24 Mbps) or Dolby True HD (18 Mbps). Since the original maximum bitrate was 3.1 Mbps this makes sense. But they also say that the maximum now for optical is 125 Mbps.

    I have Paradigm self powered computer speakers with an internal decoder. Talking with the support people they told me that their optical does not have the capacity for higher bitrates so I should use a different connector. This seems to be the popular opinion on the web.

    So I think the net of this is that losing the optical connection did not cost you in available bandwidth or quality. You have more available via the HDMI connector on the ATV4.

    But then maybe someone else can do a better job of interpreting the bandwidth data.

    As for the best audio quality, according to Apple:

    https://support.apple.com/en-us/HT204069

    Over HDMI, the Best Quality Available setting outputs Dolby Digital 7.1 or 5.1 as uncompressed LPCM. Some receivers might not show Dolby Digital as the current format, even though there's no loss in audio quality.

    So the quality that you get is determined in this case by your receiver if you've set the ATV4 to "best quality" Have you checked the audio settings for the Apple TV HDMI in port on your receiver?
     
  3. Jackintosh, Nov 7, 2016
    Last edited: Nov 7, 2016

    Jackintosh thread starter macrumors 6502a

    Jackintosh

    Joined:
    Mar 21, 2009
    Location:
    Illinois
    #3
    Good info., thanks. Yes, it appears HDMI can carry higher resolution audio than optical, although not a huge difference as I understand. But these differences seem to affect surround sound and not 2-channel, which I fall under. My receiver is audiophile quality, but is not an A/V receiver. So no HDMI inputs there, only analog along with optical and digital coax. This is why ATV3 is a better fit in the 2-channel world than ATV4.

    My concern is that previously with ATV3, the audio stream went direct from ATV3 to the receiver. Now with ATV4, the signal is required to pass through the TV then onto the receiver. The more components existing in the path, the more potential for loss. I just hope both the ATV4 and my TV leave the digital audio signal alone and simply just pass it on to my receiver.

    The point here is that audiophile quality receivers and amps usually have superior DACs, while TVs, media players (i.e. ATV), and other components only mediocre. So many listeners want their audio equipment to do the conversion to analog, not intermediary equipment earlier in the path. This is my situation.

    You asked about my audio sources. It's high res music from CDs and from my iTunes library on my Mac. Since the CD player is directly connected to the receiver, none of this is an issue. But since I also now use ATV4 to stream music from iTunes, the new and more roundabout HDMI path becomes important, and more of an issue now that the direct optical connection is no longer an option.

    As a note, I think the "best quality" option in the ATV settings only addresses surround sound, and not 2-channel audio. I may be wrong.
     
  4. HobeSoundDarryl macrumors 603

    HobeSoundDarryl

    Joined:
    Feb 8, 2004
    Location:
    Hobe Sound, FL (20 miles north of Palm Beach)
    #5
    Yes, basically, the working hypothesis is that Apple has some audio processing code running to handle voice control functions... something like decompressing, processing, recompressing. The thread Badger just linked is probably closely related to your- and my (and many others)- observation.

    This has been an issue from the launch. The defenders spin all such matters as "just a software update away" but, of course, when such updates arrive- if ever- is anyone's guess.

    There's nothing us users can do with our :apple:TVs to "fix" the issue. You'll find no solid solution here. Apple needs to address it in a software update. Be sure to report this "bug" to them. I'm certain they've read it plenty of times already but one more bug report might be the one that motivates someone inside to actually address the problem.
     
  5. Jackintosh, Nov 7, 2016
    Last edited: Nov 7, 2016

    Jackintosh thread starter macrumors 6502a

    Jackintosh

    Joined:
    Mar 21, 2009
    Location:
    Illinois
    #6
    Excellent points both above.

    And per Badger's link and thread, this is disturbing and accounts for what I and others here are experiencing. Pretty disappointing approach by Apple.

    "That's because the Apple TV 3 just passes through the audio stream. The new Apple TV 4 doesn't, it takes care of all of the decoding itself. From what I've read, the reason for this is to mix all of the sound effects and Siri into the audio stream. So, Apple can fix it, but I have a feeling that the seamless experience that we have right now with Siri will be less smooth, which in turn will probably cause even more unrest. It's a classic have your cake and eat it too dilemma."

    Looks like we might have to have an ATV3 (or Airport Express) sitting next to an ATV4. One for streaming high res iTunes music and the other for streaming video from App Store apps.

    (Sorry I missed Badger's ongoing thread on this same subject. I would have just posted my thoughts there.)
     
  6. johnborrows macrumors newbie

    Joined:
    Jul 8, 2008
    #7
  7. Richard8655 macrumors 6502a

    Joined:
    Mar 11, 2009
    Location:
    Chicago
    #8
    I saw that too and was also considering a digital extractor. But then I realized that the digital signal still carries through to the TV (via HDMI) and can then pass-through to your audio system if you use an optical cable from the TV to your amp/receiver. I did this, and along with some ATV4 audio setting adjustments, the audio now sounds just as good as with ATV3.

    Maybe someone can correct me if I'm missing something in my approach.
     
  8. Richard8655 macrumors 6502a

    Joined:
    Mar 11, 2009
    Location:
    Chicago
    #9
    The only thing that bothers me about just listening to my iTunes music library through ATV 4 is the damn TV has to be on. This is where I miss the ATV 3 optical connection option. I don't even want to see Aerial and other Apple screen savers. My TV doesn't have a screen off option to just listen to audio, unfortunately.
     
  9. priitv8 macrumors 68020

    Joined:
    Jan 13, 2011
    Location:
    Estonia
    #10
    A nice AV Receiver would solve your problem.
     
  10. LiveM macrumors 6502a

    LiveM

    Joined:
    Oct 30, 2015
    #11
    That's what the Airport Express is so good for. It has an outstanding DAC to boot.
     
  11. allonym macrumors regular

    Joined:
    Jun 12, 2009
    #12
    I use a solid black image as the screen saver. It's not distracting but you still get to see the song title notifications.
     
  12. tonyr6 macrumors 65816

    tonyr6

    Joined:
    Oct 13, 2011
    Location:
    Brooklyn NY
    #13
    I agree. I can only get mono sound on Hulu. Of course I am the only one with this problem yet someone just making up "will say app glitches once in a while with random colors and there will be 20 articles and a fix for it right away" yet I don't ever have that problem.
     

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