AAC 256: BT vs Airplay make any difference?

[flz]

For someone in the Apple ecosystem listening to AAC 256 (default lossy codec for Apple Music), would there be an audible difference between streaming it over bluetooth vs apple airplay (wifi)? I understand that airplay (wifi) will have more bandwidth but would it even matter for a lossy codec such as AAC 256? Thanks.

 

[Beershaun]

There should not be. That said Amir has found different devices implement Bluetooth aac better than others. I think if you are using apple products on both ends you should be fine.

 

[abdo123]

There should not be. That said Amir has found different devices implement Bluetooth aac better than others. I think if you are using apple products on both ends you should be fine.

I don’t remember him testing any Apple products can you link me to that?

 

[abdo123]

I would not double lossy encode stuff so I recommend that you listen to lossless on Apple Music but to continue using Bluetooth out of convenience.

 

[Zensō]

I doubt that you’ll hear a difference. This is one of those rare instances where I’d suggest trusting your ears.

 

[flz]

I would not double lossy encode stuff so I recommend that you listen to lossless on Apple Music but to continue using Bluetooth out of convenience.

If there is a way to listen to lossless from Apple Music (the streaming service) WITHOUT wires (other than HomePod which is out of my consideration), let me know. thanks.

 

[Zensō]

If there is a way to listen to lossless from Apple Music (the streaming service) WITHOUT wires (other than HomePod which is out of my consideration), let me know. thanks.

 

[flz]

View attachment 190936

Thanks. Yes, I read that article. I got confused because I thought it was only local content that would be lossless over AirPlay but the article states streaming content is also lossless over Airplay 1&2 from Mac if Airplay device is set system-wide. It sure is confusing!

 

[Chrispy]

You sure the stream will actually be via bt rather than just directing the stream from other servers?

 

[abdo123]

If there is a way to listen to lossless from Apple Music (the streaming service) WITHOUT wires (other than HomePod which is out of my consideration), let me know. thanks.

I meant activate lossless in your settings so you’re not losing data twice.

 

[Blorg]

Using AAC over BT it will decode the AAC and then re-encode it, which theoretically could lead to generational loss. It's unlikely you'd hear it though, one guy on HydrogenAudio did a re-encoding test with various codecs re-encoding them 100 times, and AAC was by far the most resistant, most of the others were mush by the end of it.

Everything I'm aware of will do a decode -> rencode step, people have this idea it can just hand the original files over to BT, but that's not how it works, it needs to decode and hand to the system mixer to mix in notification sounds, etc. and then re-encode. I'm not aware of any system that will hand an actually compressed bitstream directly to BT.

So theoretically, you would get better fidelity, even with an AAC source, sending the decoded AAC over a lossless method.

In practice, though, in terms of audibility, I suspect you wouldn't hear any difference.

 

[telemike]

Airplay 1 will get you lossless, Airplay 2 is 256AAC

 

[Zensō]

Airplay 1 will get you lossless, Airplay 2 is 256AAC

Airplay 2 via the Mac OS system interface is lossless (see the graphic above).

 

[telemike]

Airplay 2 via the Mac OS system interface is lossless (see the graphic above).

Yes, sorry. I was reffering to IOS and IpadOS

 

[Beershaun]

I would not double lossy encode stuff so I recommend that you listen to lossless on Apple Music but to continue using Bluetooth out of convenience.

I thought AAC was a natively supported bluetooth codec so it wouldn't be encoded a second time to send it over bluetooth. Is that not the case? -Hence my original post that it wouldn't be any different via bluetooth or wifi. If I'm mistaken then I change my recommendation to use wifi over bluetooth.

To answer your other question on apple products.
I was thinking of this review where Amir mentioned the AAC codec performance was degraded due to the Android implementation.

Topping BC3 Review (Bluetooth Receiver) & BT CODECs

This is a review and detailed measurements of the Topping BC3 Bluetooth receiver and headphone amplifier. It was sent to me by the online seller, Yaoyaotiger HIFI Audio Store and costs US $69. This is a follow up to our previous tests of Bluetooth receivers and investigating performance of...

www.audiosciencereview.com

As far as Apple products he's reviewed I found the homepod.

Apple HomePod Review (Smart Speaker)

This is a review and detailed measurements of the Apple HomePod smart speaker. It is on kind loan from a member and costs US $299. Apple recently discontinued them but I understand a few are still available. There is no mistake that this is a product from Apple with impeccable look and feel...

www.audiosciencereview.com

But nothing specific about the actual apple AAC implementation quality and it doesn't support bluetooth anyway.

 

[Blorg]

@Beershaun According to this, it doesn't pass the compressed audio directly, it decompresses, passes to the OS mixer as uncompressed audio, and the compiled sound stream is recompressed. My understanding, this is how all common OSes work, whether Android, Windows, Mac, iOS.

AAC provides excellent quality at 320 and 256 kb/s bit rates, but is prone to generation loss on already compressed content, however it’s difficult to hear any differences between the original and AAC 256 kb/s on iOS, even with several consecutive encodings. For MP3 320 kbps encoded into AAC 256 kbps the loss can be neglected.
Just as with any other Bluetooth codec, any music is first decoded then encoded with a codec. When listening to music in AAC format, it is first decoded by the OS, then encoded into AAC again, for transmission over Bluetooth. This is necessary to mix several audio streams such as music and new message notifications. iOS is no exception. You can find a lot of statements that iOS does not transcode music in AAC format for transmission via Bluetooth, which is incorrect.

 

[Beershaun]

@Beershaun According to this, it doesn't pass the compressed audio directly, it decompresses, passes to the OS mixer as uncompressed audio, and the compiled sound stream is recompressed. My understanding, this is how all common OSes work, whether Android, Windows, Mac, iOS.

Thanks. So is that the same for sending AAC over airplay/wifi?

 

[Blorg]

Thanks. So is that the same for sending AAC over airplay/wifi?

I don't know, in terms of how Airplay works. It would be possible theoretically for it to work differently. It's also possible, that it works one way in one mode, but another way in another mode, possibly it has one mode where it's "playing files" and not transcoding but another where it's "sending mixed audio output of the OS" and is. I'd suspect it has a chance of not, if you play a file, and that's the only thing that plays, and you make other noises on the source device and they either play locally or not at all. If the other noises are played through to the destination device, then for sure it's mixing and transcoding- although at least some versions of Airplay are lossless.

Streamers, for example, typically send/receive the original files directly, without reencoding. This is my understanding of how UPnP works, some servers will also transcode as an option, for compatibility, but it's not the default mode of operation, the default is actually just serving the files as is and the sink device receives them and plays them.

You also have systems like Tidal/Spotify Connect where there isn't any transfer of media information at all, the way these systems work is basically the player you are operating becomes a remote control, and just tells the actual playing device what it should be playing, and it then fetches that directly from Tidal/Spotify. So there's no transcoding necessary there either.

 

[Beershaun]

I don't know, in terms of how Airplay works. It would be possible theoretically for it to work differently. It's also possible, that it works one way in one mode, but another way in another mode, possibly it has one mode where it's "playing files" and not transcoding but another where it's "sending mixed audio output of the OS" and is. I'd suspect it has a chance of not, if you play a file, and that's the only thing that plays, and you make other noises on the source device and they either play locally or not at all. If the other noises are played through to the destination device, then for sure it's mixing and transcoding- although at least some versions of Airplay are lossless.

Streamers, for example, typically send/receive the original files directly, without reencoding. This is my understanding of how UPnP works, some servers will also transcode as an option, for compatibility, but it's not the default mode of operation, the default is actually just serving the files as is and the sink device receives them and plays them.

You also have systems like Tidal/Spotify Connect where there isn't any transfer of media information at all, the way these systems work is basically the player you are operating becomes a remote control, and just tells the actual playing device what it should be playing, and it then fetches that directly from Tidal/Spotify. So there's no transcoding necessary there either.

Thanks. Yes I’m aware of those options. I understand now why they are recoding for Bluetooth so other sounds from the phone can be mixed in. I am thinking about how this impacts the OPs question about whether Airplay and Bluetooth are essentially the same or not for 256 aac. I think the answer is they a different if airplay is not recoding as I don’t believe apple sends additional sounds (like notifications) in an airplay stream.

 

[flz]

Having recently acquired a WiiM Mini Streamer and SMSL Su-9n DAC, I was able to do some listening comparisons. These are just my subjective listening impressions so feel free to ignore/dismiss. The answer is yes, I thought Apple Music AAC 256 over Airplay 2 sounded slightly better than Apple Music AAC 256 over BT. In fact, I struggled to tell any difference at all between AAC 256 over Airplay 2 and lossless (either from redbook CDs or Tidal Hifi/lossless) in my system. But BT was audibly inferior by a small degree.

Some of you will say my subjective listening impressions are meaningless since I did not do a properly controlled blind test. Fair enough, but those are my impressions.