3 ms·

It's a limitation of Bluetooth's available bandwidth, especially with bidirectional audio. Apple added support for an improved speech codec, AAC-ELD, to the 3rd

by js2 4y ago

It's a limitation of Bluetooth's available bandwidth, especially with bidirectional audio. Apple added support for an improved speech codec, AAC-ELD, to the 3rd gen AirPods last year: https://www.apple.com/newsroom/2021/10/introducing-the-next-generation-of-airpods/ https://www.apple.com/newsroom/2021/10/introducing-the-next-... AAC-ELD support was also apparently added to existing AirPods Pro and Max at the same time: https://medium.marco.zone/apple-implemented-the-biggest-improvement-to-bluetooth-audio-since-2009-2079abc607af https://medium.marco.zone/apple-implemented-the-biggest-impr... I'm not sure when AAC-ELD is used on the host side though. It probably depends on the version of macOS and maybe even which app is being used. FWIW, macOS can be setup to use the AirPods for output and the built-in mic for input and that will likely result in better quality both for the person using AirPods and the person on the other end. Personally, I still use a wired headset for my conference calls. Wires are a PITA but they Just Work.

Sohcahtoa82 4y ago
> It's a limitation of Bluetooth's available bandwidth, especially with bidirectional audio. I've often read this is the problem, but I don't buy it. BTLE is up to 1 megabit. A high-quality audio stream is typically up to 320 kbps compressed. Voice can be compressed as low as 64 kbps and still sound as if the person is standing right next to you. That's still less than 400 kbps, well under the 1 mbps BTLE supports. So tell me...how is there not enough bandwidth?
- mh- 4y ago
  Not disagreeing with you necessarily, but you should know that BLE and Bluetooth are (more or less) unrelated. Confusingly.
- js2 4y ago
  It's explained in the section on SCO at the link in my original comment: > Bluetooth supports data rates of up to 3 MB/s and fully uncompressed stereo audio only needs about 1.4 MB/s. But, the 3 MB/s data rate is for an Asynchronous Connection Less (ACL) transfers under ideal circumstances. In practice, even 990 kb/s (what Sony’s LDAC codec uses) is not trivial to transmit reliably. But the Hands Free Profile doesn’t even use ACL, but Synchronous Connection Oriented (SCO) transfers. These have a fixed data rate of 64 kbit/s (bidirectional). More here: https://habr.com/en/post/456182/ https://habr.com/en/post/456182/ > Synchronous Connection Oriented (SCO) and its enhanced version Enhanced Synchronous Connection Oriented (eSCO) are the modes used for Bluetooth voice transmission. The mode allows you to transmit sound and voice strictly in order, with a symmetrical speed of sending and receiving, without waiting for confirmation of transmission and re-sending packets. This reduces the overall delay in the transmission of audio over the radio channel, but imposes serious restrictions on the amount of data transmitted per unit of time and adversely affects the quality of the audio. When this mode is used, both the voice from the microphone and the audio are transmitted to the headphones with the same quality. You should also know that (as mh- points out), BTLE is an separate protocol that is not used for audio. Audio devices use Bluetooth classic. That's also explained at https://habr.com/en/post/456182/ https://habr.com/en/post/456182/ in the "Bluetooth 5, Classic and Low Energy" section.
  - Sohcahtoa82 4y ago
    You make good points. There are certainly gaps in my knowledge of Bluetooth. > But the Hands Free Profile doesn’t even use ACL, but Synchronous Connection Oriented (SCO) transfers. These have a fixed data rate of 64 kbit/s (bidirectional). Why are we limited to HFP? Does the Bluetooth spec not allow forming two A2DP connections to establish bi-directional audio? I apologize if your link answers these questions, but it's currently throwing a 504 Gateway Timeout.
- deleted 4y ago
  [deleted]
fomine3 4y ago
Is AAC-ELD standard on Bluetooth? LE Audio is the next standard for audio.
makeitdouble 4y ago
> It's a limitation of Bluetooth's available bandwidth Other bluetooth headsets work fine, that can’t be the excuse

by js2 4y ago

Sohcahtoa82 4y ago

> It's a limitation of Bluetooth's available bandwidth, especially with bidirectional audio. I've often read this is the problem, but I don't buy it. BTLE is up to 1 megabit. A high-quality audio stream is typically up to 320 kbps compressed. Voice can be compressed as low as 64 kbps and still sound as if the person is standing right next to you. That's still less than 400 kbps, well under the 1 mbps BTLE supports. So tell me...how is there not enough bandwidth?

mh- 4y ago
Not disagreeing with you necessarily, but you should know that BLE and Bluetooth are (more or less) unrelated. Confusingly.
js2 4y ago
It's explained in the section on SCO at the link in my original comment: > Bluetooth supports data rates of up to 3 MB/s and fully uncompressed stereo audio only needs about 1.4 MB/s. But, the 3 MB/s data rate is for an Asynchronous Connection Less (ACL) transfers under ideal circumstances. In practice, even 990 kb/s (what Sony’s LDAC codec uses) is not trivial to transmit reliably. But the Hands Free Profile doesn’t even use ACL, but Synchronous Connection Oriented (SCO) transfers. These have a fixed data rate of 64 kbit/s (bidirectional). More here: https://habr.com/en/post/456182/ https://habr.com/en/post/456182/ > Synchronous Connection Oriented (SCO) and its enhanced version Enhanced Synchronous Connection Oriented (eSCO) are the modes used for Bluetooth voice transmission. The mode allows you to transmit sound and voice strictly in order, with a symmetrical speed of sending and receiving, without waiting for confirmation of transmission and re-sending packets. This reduces the overall delay in the transmission of audio over the radio channel, but imposes serious restrictions on the amount of data transmitted per unit of time and adversely affects the quality of the audio. When this mode is used, both the voice from the microphone and the audio are transmitted to the headphones with the same quality. You should also know that (as mh- points out), BTLE is an separate protocol that is not used for audio. Audio devices use Bluetooth classic. That's also explained at https://habr.com/en/post/456182/ https://habr.com/en/post/456182/ in the "Bluetooth 5, Classic and Low Energy" section.
- Sohcahtoa82 4y ago
  You make good points. There are certainly gaps in my knowledge of Bluetooth. > But the Hands Free Profile doesn’t even use ACL, but Synchronous Connection Oriented (SCO) transfers. These have a fixed data rate of 64 kbit/s (bidirectional). Why are we limited to HFP? Does the Bluetooth spec not allow forming two A2DP connections to establish bi-directional audio? I apologize if your link answers these questions, but it's currently throwing a 504 Gateway Timeout.
deleted 4y ago
[deleted]

fomine3 4y ago

Is AAC-ELD standard on Bluetooth? LE Audio is the next standard for audio.

makeitdouble 4y ago

> It's a limitation of Bluetooth's available bandwidth Other bluetooth headsets work fine, that can’t be the excuse