Audirvana 1.4.2 and Airplay

[wgscott]

I am sorry to hear about your ankle. I hope you get well soon.

 

I do apologise for my ignorance, perhaps I should have asked earlier but what is a zone player?

 

Alex

 

I'm probably using the term wrong, but there are two ways you can get music to ATV2 and ATV3:

 

1. Airplay streaming: works the same way as with airport express

 

2. "Zone player" streaming: works the same way as how you would play movies via Apple TV, except just with the audio. (I called it "zone" because you can have something different playing remotely on each of several Apple TVs, as well as the server computer).

[souptin]

I do apologise for my ignorance, perhaps I should have asked earlier but what is a zone player?

 

I can answer that one: "Zone Player" means that the Apple TV is in control - it pulls the data (music or video) from a mac running iTunes, buffers it and sends it to the screen and / or DAC via hdmi or toslink. This is a very effective solution if you suffer from severe dropouts. I think (but do not know for sure) that if the original files are 48 then there is no resampling. But of course while 48 is common for video soundtracks it is quite rare for music. B&W Music Society do some nice 48khz downloads though.

 

The 16bit or 24bit is another mystery which I've been avoiding mentioning.

 

Perhaps a future update to Apple TV will allow for third party apps, and then we might get a bit more control and insight.

[wgscott]

I should also mention that I jailbroke my ATV2 and installed the latest XBMC with the new audio-engine that can play bit-perfectly.

 

Despite this, all output from the jailbroken ATV2 was 48kHz, so the hardware and/or iOS is restricting the output.

[alex santos]

Alex: I have had the same questions, and I have asked here, the Apple Bulletin Board, etc, and never got a definitive answer. I also asked whether 24 bit, 48kHz is possible when used as a zone player, or whether it is always 16 bit. The menu settings seem to imply that 24 bit is possible, but that isn't much to go on.

 

Well I have yet to find something substantial on the 16bit or 24bit side but for now, this seems suggestive of 44.1 and 48KHz - think passthrough but I don't know if ALAC or AIFF for that matter have a passthrough component.

 

As per https://developer.apple.com/library/mac/#qa/qa1604/_index.html It relates to audio in a video stream so I maybe adding to confusion. Ignore it if that's the case but on the other hand it maybe of overall of interest.

 

"While this is not a strict requirement, be aware that if both audio tracks have different sample rates the Apple TV will default to the sample rate of the AC-3 surround audio track. If the AAC stereo audio track is being used for playback and has a different sample rate from the AC-3 surround audio track, for example the sample rate of the AAC track is 44.1kHz and the AC-3 track is 48kHz, the AAC track will be sample rate converted to 48kHz for output.

 

To avoid this sample rate conversion by the output device, content authors must encode both audio tracks at the same sample rate.

 

When Apple TV encounters a compatible .m4v or .mov file authored using the above track layout, the Dolby Digital Professional AC-3 audio track is used in a pass through mode. In other words, Apple TV will pass the Dolby Digital Professional AC-3 encoded audio data directly out to an external decoder. The AAC Stereo track is used where just stereo output is required from the device."

 

Do keep this in mind:

As per Audirvan's manual:

-iZotope 64-bit SRC best in class sample rate conversion algorithm

-Full memory play with complete loading, decoding, sample rate and format

conversion (as needed) of the tracks before playing

Technical information is given at the bottom of the LCD screen:

- On the left: Playing track file type, and native bit depth and sample rate

- On the right: The DAC current bit depth and sample rate

 

 

Also, take note of another preference setting in Audirvana…it's at 44.1KHz not 48KHz as you and I might expect.

 

I hope this helps.

[alex santos]

souptin:

 

Mystery Resolved

 

I have Wireshark installed and I would love to conduct this test myself but I need to learn how to tap into ROAP/RSTP ANNOUNCE packets.

 

But the short answer is:

 

iTunes is ALWAYS down-sampling the audio file to 16/44.1k BUT the Apple TV up-samples to 16/48KHz. The Express doesn't do anything when it receives 16/44KHz. If you want bit perfect (16/44), get an Express. For anything else just go direct to the DAC.

 

 

Here is the reference link, this was an extremely interesting read by the way.

 

I would imagine iTunes 11 has not changed it's technical behaviour when it comes to the findings posted nearly a year ago.

[wgscott]

Sorry, but where is the link?

 

Found it:

 

Am I Experienced?: Possibility for Airplay/AirTunes to Airport Express with Hi-Res Audio

[alex santos]

wgscott:

 

Yes that is the link. Sorry it was rather late when I posted, thanks for filling in the gap!

[BoneIdle]

Hi, just wanted to ask if anyone knows how I run Audirvana directly, like you can with Decibel? In the case of Decibel, I use Airfoil, select Decibel as application and Apple TV as output and it plays through my DAC from Apple TV; this doesn't work in Audirvana, I get no sound? Any help much appreciated! Thanks.

[damien78]

Hi, just wanted to ask if anyone knows how I run Audirvana directly, like you can with Decibel? In the case of Decibel, I use Airfoil, select Decibel as application and Apple TV as output and it plays through my DAC from Apple TV; this doesn't work in Audirvana, I get no sound? Any help much appreciated! Thanks.

 

With 1.4.4 Airfoil gets detected automatically, before it, you need to manually deactivated Direct Mode in A+ user prefs as Airfoil is hijacking the audio signal inside CoreAudio (that Direct Mode bypasses).

 

You can get the playlist mode by unselecting "iTunes integrated mode" in the "Audirvana Plus" menu. But note that Airfoil works in both modes.

 

Damien

[BoneIdle]

Many thanks Damien, that worked a treat!