192/24 on Apple TV 3?

Discussion in 'Apple TV and Home Theater' started by kaldezar, Sep 18, 2015.

  1. kaldezar macrumors regular

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    #1
    Does anyone know if the new Apple TV supports streaming of 192/24 files, specifically that it outputs at those values or does it still downgrade to 44.1/16 bit?
     
  2. priitv8 macrumors 68020

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    #2
    Unless they have changed something completely at the AirPlay protocol, no.
    AFAIK, despite using ALAC stream over the air, it is still 44.1/16bit.
    Speaking of unjailbroken, Apple-provided tvOS, of course.
    And, obviously, extending the protocol would call for changes on the OS X and iOS end as well.
     
  3. likethesoup2 macrumors 6502a

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    #3
    Apple really needs to catch up to the rest of the world as regards hi-rez sound.

    It is simply befuddling to me why they won't put a full size USB connection. I presume this is a remnant of the Jobs days of us 'not knowing' what we need/want. It was wrong then and it's wrong now.

    And that fact alone -- along with having to purchase another device (that's almost as expensive as the ATV) in order
    to push sound to my outboard dac -- will probably keep me from purchasing.
     
  4. Uofmtiger macrumors 68000

    Uofmtiger

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    #4
    Just for clarification, the AppleTV (2 & 3) does not send out a 44.1 signal. Everything is sent out as 48khz. The Airport Express sends out only 44.1.
     
  5. priitv8 macrumors 68020

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    #5
    That may be what's happening on it's back ports. But AFAIK what is flown over the air, is still 44.1/16. Check this page for example:
    http://git.zx2c4.com/Airtunes2/about/#constants
    or check any other implementations of RAOP client. E.g here
    https://code.mythtv.org/doxygen/mythraopconnection_8cpp_source.html
    one finds m_channels(2), m_sampleSize(16), m_frameRate(44100),
    So, one can conclude, that the audio stream gets down/upsampled on the sender and receiver side, as needed. But from what I understand, 2 channels, 16 bits per sample and 44100 samples per second are hardcoded into AirPlay protocol.
     
  6. Uofmtiger macrumors 68000

    Uofmtiger

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    #6
    Yes, I was responding to his statement about the OUTPUT of the AppleTV as it related to the 2nd and 3rd gen models. I was not referring to Airplay's capabilities, which is a different subject, because the AppleTV can also get its music files via Home Sharing or via iTunes Match. If you have 24/96 files or 16/44.1 in your iTunes library, they will be resampled to 48khz. Airplay, which is 44.1 will also be resampled to 48khz with the AppleTV (2 and 3).

    To be clear, I was saying that everything on the AppleTV 2 and 3 is output at 48khz (not 44.1).
     
  7. priitv8 macrumors 68020

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    #7
    OK, agreed. But to the OP's question - these conversions make 192/24 playback from aTV a nonsense, because the stream may be resampled along the way several times, and none of the intermediaries maintains the original bandwidth.
     
  8. JAT macrumors 603

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    #8
    Why/how would aTV come into the picture for high-rez streaming? Wouldn't anyone caring about such audio files already have a more-capable preamp/receiver that could simply receive via network? Are we plugging in the puck just to have an Apple Device in the mix? Mine has built-in networking, Airplay, and I just run an HDMI direct from the Mini, anyway.
     
  9. Snoopy4 macrumors 6502a

    Snoopy4

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    #9
    I must admit I'm confused by this. They added 7.1 to the audio capability for movies but left this out for music.
     
  10. Uofmtiger macrumors 68000

    Uofmtiger

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    #10
    Not necessarily. Home Sharing will send high resolution files in their original format, at least to 96khz, which I have tested ( don't know about 24/192). While AirPlay is currently 44.1, there is nothing saying that they can't improve on that technology. DLNA, for example, can handle higher resolution streams.
    The first, and main, reason is that they might want high resolution audio from movie soundtracks. Specs for Dolby Digital True HD, for example, goes up to 24/196.

    If Home Sharing on the AppleTV, handled higher resolution files, it would provide a superior interface for playing music from iTunes running on a computer somewhere. Plex, which has been announced, would be a great interface for playing music from a NAS. The interface for receivers isn't typically up to those standards. For most receivers, you need an app on a mobile device or a computer to control what is playing. Many would prefer to use just use a remote that controls playback from the TV.

    I want to mention that my main concern would be for bit perfect playback of whatever signal it is sent....especially, 16/44.1 which is not bit perfect on playback thanks to the 48khz upsampling with the AppleTV 2 & 3.
     
  11. priitv8 macrumors 68020

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    #11
    In which scenario does Home Sharing send files in HR?? Or are you speaking about movies??
    IMHO whenever you play music from your iTunes library on appleTV, you are using AirPlay (even over a cable). So I don't get your point here.
    But sure, I have created some of quadraphonic audio files myself as M4V movies just to play them back on 4-channels. Still, I have to use AC3, which by definition maxes out at 640kBps, which is the total bitrate for all 6 channels.
     
  12. Uofmtiger, Sep 20, 2015
    Last edited: Sep 20, 2015

    Uofmtiger macrumors 68000

    Uofmtiger

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    #12
    No, I am talking about music:

    http://www.innerfidelity.com/content/audiophile-play-ipad#s9t6lpXfO6HgGPyM.97

    Home Sharing is not the same thing as AirPlay:

    https://support.apple.com/en-us/HT202190

    Currently, the AppleTV is converting everything to 48khz. However, Home Sharing is, or was ( haven't tested it * since iOS 9 was released), compatible with high resolution files a camera connection kit and a compatible DAC on iOS.

    *Edit: Went ahead and tested it with my iPhone and it still works ( at least to 96khz, which is what my Dragofly DAC supports).
     
  13. priitv8 macrumors 68020

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    #13
    Interesting! I will check on this.
    That part is clear. But nowhere does it say that audio stream is transported differently when using Home Sharing. I have so far understood, that HS is mostly about authentication. Thus, I presumed the transport is still the same old RAOP.
     
  14. Uofmtiger macrumors 68000

    Uofmtiger

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    #14
    Per wiki:

    The AirTunes part of the AirPlay protocol stack uses UDP for streaming audio and is based on the RTSP network control protocol.[8] The streams are transcoded using the Apple Lossless codec with 44100 Hz and 2 channels encrypted with AES, requiring the receiver to have access to the appropriate private key to decrypt the streams.[9]

    As per the above, I think the main difference, as it (currently) applies to Airplay for music, is that it currently transcodes all streams to 16/44.1. Home Sharing does not transcode to a different bitrate. In other words, if I have a 24/96 file in iTunes and Airplay it, the file is automatically transcoded on the fly to 16/44.1. With Home Sharing, on iOS, the file will play in its native bitrate. I believe it works more like "sharing" when you access a file on a NAS from a laptop. It is simply sharing access to the file rather than sending it through its Airplay protocol.

    For me, it is easy to see with a Dragonfly DAC because it has an illuminated Dragonfly that lights up when it receives a signal. It is pink (magenta) when it receives a 96khz bitrate and green when it receives a 44.1 bitrate. I have a couple 24/96 files and the Dragonfly is magenta when played. I have a Youtube video showing how this works with the iPad, but I wasn't using Home Sharing in the video, but you can see how the Dragonfly changes color (if you are interested just Google "uofmtiger ipad dragonfly" and it should pop up).

    In any event, the AppleTV currently take all signals and converts them (if necessary) to 48khz for output. Personally, I would be much happier if it played all music at its native rate. Currently, even 16/44.1 (Redbook/Airplay) is being converted. I would prefer "bitperfect" audio.
     
  15. priitv8 macrumors 68020

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    #15
    Thanks man, that was edutainment!
    The referred pages are all about using iPad as the playback device for HR-audio. But does aTV play them as well? I believe I did try once with some ALAC files in 24/192. While I could play them via optical out from my MBP, I don't recall aTV playing them back. I need to retest. FWIW I heard the most sound improvement from my almost classic receiver, when I switched the Mac output from Integer to Floating point! And my receiver does not do 192bps, so I had to set in MIDI-Setup 96 and Core Audio does the rest.

    It may really be true, that via Home Sharing the whole contents of the file is transported over the network as-is. And the HS authentication takes care of the encryption part.
     
  16. Uofmtiger, Sep 23, 2015
    Last edited: Sep 23, 2015

    Uofmtiger macrumors 68000

    Uofmtiger

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    #16
    I believe the AppleTV (2 and 3) will play them, but it transcodes everything to 48khz.
     
  17. priitv8 macrumors 68020

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    #17
    OK, I will have to test how mine behaves.
     
  18. DblHelix macrumors regular

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    #18
    With the right app and dac you can do 24/192 as well as 24/384 and dsd (same as SACD)
     
  19. ChrisA macrumors G4

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    Redondo Beach, California
    #19
    24-bits works well for recording and mixing. It has such a dynamic range that you can be a little lazy setting the levels. Internally the software might use 32-bit samples but for distribution 16-bits works well. After all who has equipment that can reproduce a 144db dynamic range? Same with the sample rate. Who has hearing or equipment that can reproduce 96KHz

    But when we record we use 24/96 because we are going to process the heck out of it, even if just adding a touch of reverb and compression. Those alone are a LOT of math and the hight bit and sample rates help with round-off error

    Also look at the source. What microphone and preamp was used to make the recordings? Both of the will have noise with limits the recording no matter how you play it back.
     
  20. Irishman macrumors 68030

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    #20
    Why 192? There's no sonic benefit over 96.
     
  21. priitv8 macrumors 68020

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    #21
    So, finally arrived at short testing. At the end of the day, do I need a HDMI connection from aTV to the amp?
    Over the optical, I can only see 2304kbps at 48kHz, irrespective if I play a 320k MP3 or 24/192 ALAC.
    TOSLink.jpg
     

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