Audio codec used over bluetooth by an iPhone?

I hope it doesn't bother you that reply after more than one year 🙂

This thing is weird that Apple doesn't provide the most suitable profile for Bluetooth audio devices, while at the meantime they're now promoting those Bluetooth earphones.

I bought Sony MDR-1000x several months ago. The sound does satisfied me to some extent, but I did noticed the gap between wireless mode and wired mode. I also confirmed that this earphone supports SBC/AAC/aptX/LDAC (http://helpguide.sony.net/mdr/1000x/v1/en/contents/TP0001176186.html), and the earphone's "quality mode" will try to use the modes other than SBC. But macOS still uses SBC for my device. Weird enough.

The solution is to turn "Enable AAC" on in the "Audio Options" panel of Bluetooth Explorer (the tool you mentioned), or turn on "Force use of aptX". When this is done, the connection does switch to AAC codec now.

I cannot fully understand Apple's thoughts on this problem, but I do hope there'll be further improvement that suits the standards of contemporary products. (Why not just support Sony's LDAC standard lol)

In Apple's developer center. Named "Hardware IO Tools for Xcode 7.3". Within the dmg image, you can find

Bluetooth Explorer 4.4.0.

I uploaded the dmg file, so you can also use this link: https://www.dropbox.com/s/9qwrznu5lm9kk69/Hardware_IO_Tools_for_Xcode_7.3.dmg?dl =0

P.S. I also think the AAC Bitrate should be pulled to max, which wasn't revealed in the picture I posted.

I have the same question since new models no longer provide 3.5mm port. Wireless (bluetooth) headphones with decent hardware sound quality should provide better experience.

i called apple support, and according to them, iOS will select the best encoding format if receiver also supports.

In this case, if your headphone support AAC, then the entire process should be the following flow

mp3/aac/alac/flac -> PCM (ios decoder) -> AAC (ios encoder for bluetooth a2dp protocol and received by headphone) -> PCM (headphone decoder) -> DAC into analog signal (headset) -> amplifier-> Sound you hear

apart from the source file quality, the AAC for bluetooth transmission is also crucial for the final sound quality you can get. In this case, for good sources which are better than aac format, you can get better sound if your headset support aac transmission, for those lower rates source files, it really makes no big differences if your headset only support SBC or AAC as well.

Thanks for your help! All working now, will see if there is any different. My sharing now - got the BTE v5 via the Xcode add-on. Hope it helps the others. Regards

Here's a partial answer for you.

You are correct that the codec chosen for Bluetooth A2DP is irrespective of the source's codec. However, you can't assume that AAC will always be chosen, in your example. While I would hope that both the iPhone and the Bluetooth speaker would attempt to negotiate the highest-quality, mutually-supported codec and bitrate, the reality is that the Bluetooth link quality will be a factor. So it's conceivable that if the iPhone and speaker are sufficiently far away from each other, and/or are experiencing interference, that they might negotiate a lower AAC bitrate, or fallback to another codec like SBC, even though they support high-bitrate AAC. The part I don't know is, are the Bluetooth implementations (on both sides of the A2DP link) smart enough to adjust the codec and bitrate as conditions change? Also, as you point out, it's difficult to impossible to figure out which codec is in use; you could probably get some Bluetooth "sniffing" software to try and figure it out, but I haven't tried. On a Mac computer, you can hold down Option while looking at an active Bluetooth connection to see which codec is in use.

I'm using the Apple BlueTooth explorer ver 4.3.0 and the validation ver 4.3.0 tool on a Macbook Air 13 medio 2012.

When I run the validation tool on a receiver I have it confirms it supports AAC - also AAC VBR. "Supports AAC with variable bit rate"

When I set the audio options in the explorer to disable AptX - and reconnect the device it runs SBC codec.

I think it should select AAC in that case. Why doesn't it do that?

Hi there, where did you get this version of Bluetooth Explorer? mine is 4.3.0, and I couldn't see the button "Enable AAC", thanks! I just want to force the AAC too!

Hi, I also have purchased these headphones and looking to optimize the bluetooth connection from my iphone 5s. Do you have any tips for this eg, AAC etc?

Thanks