macOS fixed sample rate and bit depth output

[Wicky]

Apologies if this has been covered on other posts, a quick search did not reveal the information I was seeking.

Using a macOS (iMac) as a Roon Core, output via USB to both RME ADI DAC & HIDIZS S9 I found the sample rate received by the DAC did not dynamically change in accordance with the source music file (at least according to the DACs reading).

I've taken the approach of setting the output in macOS Audio MIDI Setup App to 192kHz, I've assumed the DAC is downsampling the input for source material above that rate and that Roon is upsampling source material below those rates.

Are my assumptions correct?

If so, is the upsampling/downsampling sub-optimal in the audio chain?

Thanks!

 

[Wicky]

I eventually managed to find another thread on ASR which tackles these questions here:
https://www.audiosciencereview.com/...end-audio-from-macbook-to-external-dac.14245/

And some detailed analysis and measurements by Archimago here:
http://archimago.blogspot.com/2015/11/measurements-apple-mac-os-x-yosemite.html

As I've understood conclusion, upsampling and downsampling is all performed in macOS Core Audio from the source player and that these operations do not introduce significant distortion to the signal. I therefore will be setting the Audio MIDI Setup output to 24/192 as this is at the limit of the bit depth/rate I have in my source material and will let Core Audio upsample everything else.

 

[chelgrian]

Using a macOS (iMac) as a Roon Core, output via USB to both RME ADI DAC & HIDIZS S9 I found the sample rate received by the DAC did not dynamically change in accordance with the source music file (at least according to the DACs reading).

It's up to the software to change the sample rate of the audio device as required. For example Swinsian has an option to change the device rate to match what is currently being played. That certainly works with my ADI-2 DAC.

If Roon doesn't have this option then you'll end up having to choose a rate and have everything resampled to that rate.

As far as I'm aware roon believes that it should be doing the resampling as part of its 'DSP engine' and that you should set that to some rate and the audio device to match.

 

[dpippel]

The macOS versions of Tidal, Qobuz, Roon, etc. all allow you to set the output device to Exclusive Mode if supported (most DACS), which turns on bitperfect output from the OS to the DAC. My Roon Core resides on a Lenovo box running Windows Server, and I stream from there using my MacBook Pro as an endpoint, outputting to a RME ADI-2 DAC. No problems. Same with Qobuz and Tidal.

 

[Wicky]

Thanks @chelgrian & @dpipplel, both useful answers. @dpipplel I will certainly investigate 'Exclusive Mode' in Roon as I have not come across this yet. I'm a new Roon user, starting with it this year.

 

[DeepSpace57]

The macOS versions of Tidal, Qobuz, Roon, etc. all allow you to set the output device to Exclusive Mode if supported (most DACS), which turns on bitperfect output from the OS to the DAC. My Roon Core resides on a Lenovo box running Windows Server, and I stream from there using my MacBook Pro as an endpoint, outputting to a RME ADI-2 DAC. No problems. Same with Qobuz and Tidal.

And interestingly there is no `exclusive mode` for Apple Music on MacOS

 

[dpippel]

And interestingly there is no `exclusive mode` for Apple Music on MacOS

Quite an annoying omission on Apple's part, especially considering their move to lossless and Atmos. As it stands now, you either have to upsample/downsample through macOS midi audio or deal with the (for me) inconvenience of using an iPhone or iPad to get bitperfect audio streamed from Apple Music. Pretty lame if you ask me.

 

[Jazz]

I do not understand why Apple has not fixed the lack of exclusive mode bit perfect yet. They release Lossless but it is not fully usable on macOS.

 

[Jazz]

This THX PDF page pretty much lays it down (as of Oct. 15, 2021) in clear language for their little DAC but, it is all applicable to most other USB DACs and Apple Music on a Mac. For now…
Set Audio MIDI to 24 bit 176.4 kHz on macOS.
Since BitPerfect is abandonware and, supposedly does not work for streaming and, if like me, you have no interest in Roon, Audirvana, Tidal, or Qobuz, the THX advice for macOS is the best and, really not a terrible option. Alternatively, just use a wired iOS device on you high end stuff.
https://www.thx.com/wp-content/uploads/2021/06/THX-Onyx-for-Apple-Music-Lossless.pdf

 

[Norv]

GitHub - vincentneo/LosslessSwitcher: Automated Apple Music Lossless Sample Rate Switching for Audio Devices on Macs.

Automated Apple Music Lossless Sample Rate Switching for Audio Devices on Macs. - vincentneo/LosslessSwitcher

github.com