This question, from 2012, asks whether there is loss in the signal quality of an Apple-Lossless-encoded file when transmitted from a Macbook to an Airport Express.

I am wondering whether things are any different in 2016 when transmitting an Apple-Lossless-encoded file from a Macbook to a 4th gen Apple TV. Clearly Wifi is plenty able to transmit the file intact. With an HDMI connection to the TV and an Optical (audio) connection from the TV to the receiver, I should in principle be able to listen to an intact file.

  1. Is it still the case in 2016 that lossless files go through an encode-decode cycle?
  2. Is there any configuration that makes me say "use all available WiFi bandwidth, but let me listen to the original file"?
  3. Is there any configuration that says "drop the video signal (for example, just display a static image of the cover of the album), and transmit the audio signal intact"?

Granted, this is not to be done for an extended period since the TV must remain on. Unlike the 3rd gen Apple TV, the 4th gen does not provide direct optical-out to the receiver.


1 Answer 1


I'm assuming you're talking about AirPlay Screen Mirroring from a Mac to an Apple TV. In that case, yes, you are loosing signal quality from compression-before-transmission and decompression-after-reception.

In particular, the audio part of the AirPlay Screen Mirroring is compressed using the AAC-ELD codec to ensure low-latency sound encoding. However, there is a signal loss involved.

  • By "I'm assuming" you're leading me to think that there is another way to Airplay to a 4th gen Apple TV. As I'm mentioning in the question, the 4th gen has no audio out, just HDMI out. This leads me to believe that the 4th gen does not have Airplay audio-only mirroring. But I'd love it if you can tell me this is incorrect.
    – Calaf
    Jun 2, 2016 at 17:00
  • There are others ways to AirPlay, yes. When you AirPlay a movie from your Mac (using an AirPlay compatible player ofcourse), a different protocol is using than when using screen-mirroring. In essence the Apple TV would then fetch the original video source directly instead of getting a re-encoded screen mirror image from the Mac. This also means that it receives the original audio part of the video source directly - so the audio part will not be reencoded for transport by the Mac.
    – jksoegaard
    Jun 3, 2016 at 10:17
  • That's very helpful to know. But it just struck me that we're still talking about two different issues. You're talking about video+audio. I'm talking about just audio. Now you can perfectly well reply that the 4th gen Apple TV was never meant to receive just music, and I already suspect that that was Apple's intention. I'd say that the issue is then closed. Those who want to listen to their lossless music collection must use a tethered connection. Airplay will not do.
    – Calaf
    Jun 3, 2016 at 12:04
  • I'm not sure why you have that idea. I can send audio to my 4g Apple TV without any problems (yes, just audio - not video). You'll need to connect your audio equipment via HDMI ofcourse.
    – jksoegaard
    Jun 3, 2016 at 20:36
  • I'm curious: during which years did it become pseudo-standard for receivers to receive video inputs?
    – Calaf
    Jun 5, 2016 at 12:44

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