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Curiosity question: What is "worse"... audio playing through AAC Bluetooth codec or having the audio upsampled to 48kHz?

euge_lee

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First, it's more of a mental exercise than one I believe I can actually discern between, especially when listening in a car.

But... if you had a choice of a good 44.1kHz/16 bit lossless audio source playing through the stereo... and you had to choose between it being transmitted over Bluetooth using the lossy AAC codec... or you can play it "directly" but the audio must be resampled to 48kHz... which is "worse"?

Detailed Info: I use Roon and in my Tesla... there's no "aux in" and normally, there's no Apple CarPlay. Using a Raspberry Pi and a custom software build for it called TeslaAndroid (https://teslaandroid.com) I am able to have CarPlay in my Tesla.

One way to listen to music is to use either Tidal or Roon ARC on my iPhone via CarPlay but that method sends audio to my car via Bluetooth. Tesla only supports AAC Bluetooth codec so i will be lossy Bluetooth.

Another way is to use the Raspberry Pi (running Android 13) which gets displayed on the Tesla via the Tesla browser. The audio playing through the browser is a very clean "lossless" audio stream but because of the nature of the Android OS... it resamples everything to 48kHz.

Now... none of this is truly "crucial" because it's in a car and I honestly can't tell the difference either way... but as I was setting up and playing with Tesla Android in the car, it made me think and wonder which is the lesser of two evils if I had to choose.
 

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JSmith

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But... if you had a choice of a good 44.1kHz/16 bit lossless audio source playing through the stereo... and you had to choose between it being transmitted over Bluetooth using the lossy AAC codec... or you can play it "directly" but the audio must be resampled to 48kHz... which is "worse"?
I'd go for the conversion to 48kHz over compression with AAC, however as you note in practice there's probably not much difference in it.

Most of the time, except with very poor conversion algorithms (which do exist), the differences in quality is small enough that you will not be able to differentiate just by listening. With the better algorithms you can only tell the differences by measuring.


JSmith
 

amirm

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But... if you had a choice of a good 44.1kHz/16 bit lossless audio source playing through the stereo... and you had to choose between it being transmitted over Bluetooth using the lossy AAC codec... or you can play it "directly" but the audio must be resampled to 48kHz... which is "worse"?
Assuming the 48 kHz resampling is half decent, by far that path instead of AAC. In my listening tests, AAC over Bluetooth sounds terrible. LDAC is the only choice to use if you anything near transparency.
 

MaxwellsEq

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AAC with Bluetooth will always be poor. Upsampling to 48kHz may be brilliant if done properly. If done badly it may suffer low levels of aliasing and imaging, but these are unlikely be audible in a car.
 

abdo123

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Yeah Bluetooth is a no go when it comes to sound quality in general. Something about real-time transcoding makes it inherently bad. I'm more than okay with regular AAC or MP3.
 

Mnyb

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Resampling can be done perfectly preserving all fidelity or close enough . Lossy Codecs are by definition lossy BT and AAC so here it depends
 

ZolaIII

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As much as I have a short read on the topic solution is hot-spot tethering contentton from the phone so that you can use in built streaming service's in full (as good as they are and as good their integration is) on tesla infotainment sistem and avoiding to pay 10$ a month for Premium Connectivity. That way you can get Tidal losses without resampling (hopefully) and additional costs but only in areas where you have good cellular connectivity. Anyway as it cost's you nothing you should try.
Best regards and have a nice time.
 
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euge_lee

euge_lee

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Assuming the 48 kHz resampling is half decent, by far that path instead of AAC. In my listening tests, AAC over Bluetooth sounds terrible. LDAC is the only choice to use if you anything near transparency.
It shouldn't be much different than a typical Android phone/tablet in terms of upsampling "quality" as that's done by the Android OS I think? And isn't hardware dependent?
 
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euge_lee

euge_lee

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As much as I have a short read on the topic solution is hot-spot tethering contentton from the phone so that you can use in built streaming service's in full (as good as they are and as good their integration is) on tesla infotainment sistem and avoiding to pay 10$ a month for Premium Connectivity. That way you can get Tidal losses without resampling (hopefully) and additional costs but only in areas where you have good cellular connectivity. Anyway as it cost's you nothing you should try.
Best regards and have a nice time.
So the "Tesla integration" (which I can do as I have lifetime premium connectivity) is lacking in that for "master/lossless" audio, you need to download the tracks. Streaming is limited to 160kbps. The setup I have with the Raspberry Pi also has an LTE modem added, so I can use the Android Tidal app and actually stream master/lossless without pre-downloading.
 
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Its in a car, it barely matters..
So. With that statement you have the opinion that all ears and all cars are the same. -Nice. :facepalm:

Audio in cars can be of significant high quality. It's not all 2 x 12 " subs in the trunk of a Honda Civic from '98 you know.

In this instance it's a Tesla. One of the least noisy cabins on the road and with a decent sound system.
 

pallatin

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Is AAC over USB (not bluetooth) fine for audio quality? Or just don't bother with it, and go with some kind of lossless instead?
 

kongwee

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You DAC which normally SDM will upsampling into 11.Mhz.
 

MaxwellsEq

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Is AAC over USB (not bluetooth) fine for audio quality? Or just don't bother with it, and go with some kind of lossless instead?
Go lossless if you can. In blind tests, MP3 & AAC (effectively the next generation of MP3) at 320kbps is hard to distinguish from WAV or FLAC. However, if you've got storage space and bandwidth, why throw away content of you don't need to?
 

pallatin

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I just like YouTube Music somehow, and feel the audio coming out of it is more than fine, I honestly cannot distinguish from Apple Music Lossless with my current equipment.
 

JohnBooty

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Assuming the 48 kHz resampling is half decent, by far that path instead of AAC. In my listening tests, AAC over Bluetooth sounds terrible.
In your BT+AAC listening tests, was the source material lossy or lossless?

Here is my subjective experience:
  • Lossy source material --> Bluetooth AAC --> Terrible sound. Presumably due to the recompression. Comparable to low-quality mp3s downloaded from Napster or wherever back in the dark ages.
  • Lossless source material --> Bluetooth AAC --> Very acceptable sound. Comparable to high bitrate properly encoded AAC/mp3. Not distinguishable from lossless unless I really focus on specific small details.
The lossy listening was done with a variety of iPhones and various headphones including Bose QC45. For some of the older Sony headphone models, enabling AAC was a manual step and I performed that step.

The lossless listening was only with iPhone 12 + Bose QC45. I'm quite certain that there is not anything special about this combo, but since implementations do vary, I guess it's worth noting.
 
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