AAC files recognized at incorrect sample rate

Core Machine (Operating system/System info/Roon build number)

QNAP T-473

Network Details (Including networking gear model/manufacturer and if on WiFi/Ethernet)


Audio Devices (Specify what device you’re using and its connection type - USB/HDMI/etc.)

PC optical to Modi Multibit

Description Of Issue

When copying iTunes AAC files from PC that are sampled at 16/48khz to my room core they get recognized as 44.1kz. The files seem to actually be changed during the copy (lengthened, largened). This makes them play slowly due to the incorrect sample rate. Oddly enough, If I convert them to lossless AAC before copying, they are copied/recognized correctly as 16/48 and play just fine. I’d like to avoid having to pre-convert them as it takes up ~4x the space (lossless forces 1000 kbps instead of the native 257).

I’m not sure why the change, but I have to correct you on “lossless aac”. AAC never was and never will be lossless, or anywhere neaR that. It is Apple’s answer yo. MP3.


Most of my library is FLAC or DSD so I understand. I’m simply using the itunes language for their codec since they are both AAC. They call it “lossless” or ALAC. I just find it odd that the base version at 257 kpbs transfers correctly, but when changing that same file to ALAC (at the same sample rate), it correctly imports. Also, the “lossless” AAC is not far off your typical FLAC file (16/48, ~1000kps). It’s more in line with CD audio than mp3.

I have music on there that I can’t obtain otherwise and would like to add it to my Roon library.

Alac has nothing in common with aac except being Apple. Even if recorded at 44.1/24, aac, imho, does not sound anywhere near as good as red book 44.1/16. When I first started using Roon, I deleted my iTunes/ Apple Music library of well over 100k aac files, as they totall lost the only advantage they had, portability with ease. They never sounded that good, even on an iPad, but iTunes / Apple Music was a great portability platform. Now, with Roon firmly in my blood, there is no way I will ever use aac again.

AAC files dont have a sample rate or bit depth due to encoding system much like MP3 doesn’t . The sample rate and bit depth are only a thing when the files are decoded to PCM which can be arbitary. Roon does this to 48/24 if I remember correctly for any lossy stream.


And that is the issue, it is importing them as 44.1khz.

Have you encoded these your self! Why are they 48/16 when cd is 44.1 to begin with. Roon will import them based on what the file tells it. The decode rate Roon uses is unrelated to import. All mine are shown as 44.1/16 but playback in Roon at 48/24 as that’s their chosen decode rate as it apparently gets them to sound better.


I agree that AAC doesn’t sound as good. Converting AAC to ALAC is just a waste of space you can see as I’m converting a 257 kbps file into a ~1000 kbps file for the sake of it importing at the right sample rate.

Portability is still an factor for me (listening on the road), so I’ll keep my itunes library. Also, I would never delete these files even if some of them are inferior as most of them can’t be recovered or found elsewhere (rare live recording etc). Hence my desire to import some of them to my Qnap core for safe keeping.

The AAC files are natively 48 khz when downloading them from apple. These are the files that have an issue. Again, oddly if I duplicate them as 16/48 ALAC, they import just fine as such.

Are these Apple purchased AAC then?

Many of them are yes.

Maybe I should clarify as well that I’d like a better solution than spending countless hours duplicating 1000’s of files in a different format and rebuilding my roon library. I feel like there is something off if Roon is importing at the wrong sample rate. I am directly dragging and dropping the files from my itunes directory to my roon core server.

As far as I know airplay can’t play over 44.1 for music so this would mean they would not work on airplay without downsampling which seems at odds for Apple to supply incompatible files. Did it say on the store they where 48 seems suspect that some metadata is off here. I am no Apple expert though. And as I said AAC doesn’t really have a sample rate or bit depth so it should not matter. I have quite a few Apple purchased AAC and all work with no issues. I wonder if it’s a weird permission thing?

I have thousands of AAC files, both self-ripped and purchased from the iTunes Music store. Every single one of them is 44.1 kHz. Where did you get the impression that Apple Music downloads are 48 kHz?

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I have been downloading tracks from iTunes since iTunes was introduced and none of the AAC files I have are 16/48. They are all 16/44.1.


I also have 1000’s, they are all 48khz and play perfectly within itunes. I can post a pic if necessary.

Same here brother. This is so confusing to me. Like I said I have literally thousands at ~250 48 khz.

I wonder if iTunes on Windows is incorrectly reporting the sample rate. I’m on macOS.

Possible, BUT they play fine in itunes and in windows they show the same sample rate. Once they are imported to my QNAP Core (drag and drop), they are larger files because the sample rate is 44.1 khz, and then are subsequently “slow” in Roon (like they are playing in slow motion). I can’t find anyone else with this same issue and its driving me crazy!

You ripped or converted them to 48kHz since Apple has always used 44.1kHz for the iTunes library.