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Audio over Bluetooth: detailed information about profiles, codecs, and devices

34 points by MrBuddyCasino 4y ago

JohnFen 4y ago
A fascinating treatise -- and it explains why I can't seem to find any bluetooth headphones that sound as good as wired headphones do. So, having an earphone jack remains indispensable for me, even if I do also use Bluetooth for certain situations.
- ugjka 4y ago
  What about usb-c headphones?
  - knaik94 4y ago
    Most of them add a not insignificant amount of noise to the sound. It's really obvious when you use compare the sound from a headphone jack with to the sound of the usb c or USBc to 3.5mn adapter on the same phone/tablet/computer. In my experience it's not a OS level difference either. Additionally, I can't charge and play music at the same time with usb c headphones. At the very least I would want two usb c ports in order to have feature parity with what I would be giving up.
  - JohnFen 4y ago
    I've never tried them. My phone has an earphone jack, so if I'm going to be wired, I use that -- which leaves the USB-C port available for other things. But do USB-C headphones avoid compressing the audio?
  - atoav 4y ago
    USB-C headphones need to essentially host the USB controller, some microcontroller to coordinate it all, DAC (Digital to Analog Converter) and a suitable amplifier to drive the actual speakers. And that amplifier very likely needs more than the 5V coming over USB C so you need some sort of DC-DC boost converter that is dead silent and stable so it plays the transients clearly. Getting this all right in such a constrained space is possible, but as all things analog it requires some serious engineering and not just a "we throw that one good chip on and we'll be good". IMO you still fare better by getting decent cans and even a cheap USB soundcard like the Behringer UMC series.
liminalsunset 4y ago
Given this came out in 2019, notably absent is any mention of Bluetooth LE Audio, Bluetooth 5.2, and the new LC3 codec, which may resolve some of the problems mentioned here.
- rasz 4y ago
  LC3 will certainly resolve any potential Fraunhofer funding issues. Another patent encumbered codec when we could have settled on OPUS.
  - liminalsunset 4y ago
    I was under the impression that it was LC3plus, not LC3, that was encumbered. The LC3 codec appears to be part of the open Bluetooth specification, and its role in replacing the former "free to implement" SBC appears to suggest this. Supposedly, I have read somewhere that LC3 uses some similar methods to Opus, and bears some form of technical resemblance (and hence inherits the benefits of) Opus. I have heard of someone I know using Opus directly to do some form of proprietary wireless low latency audio transmission, so it might actually be feasible, though it was noted that Opus decoding consumed a lot of microcontroller resources, which may be the real driver behind developing a "low complexity" codec.

34 points by MrBuddyCasino 4y ago

A fascinating treatise -- and it explains why I can't seem to find any bluetooth headphones that sound as good as wired headphones do. So, having an earphone jack remains indispensable for me, even if I do also use Bluetooth for certain situations.

ugjka 4y ago
What about usb-c headphones?
- knaik94 4y ago
  Most of them add a not insignificant amount of noise to the sound. It's really obvious when you use compare the sound from a headphone jack with to the sound of the usb c or USBc to 3.5mn adapter on the same phone/tablet/computer. In my experience it's not a OS level difference either. Additionally, I can't charge and play music at the same time with usb c headphones. At the very least I would want two usb c ports in order to have feature parity with what I would be giving up.
- JohnFen 4y ago
  I've never tried them. My phone has an earphone jack, so if I'm going to be wired, I use that -- which leaves the USB-C port available for other things. But do USB-C headphones avoid compressing the audio?
- atoav 4y ago
  USB-C headphones need to essentially host the USB controller, some microcontroller to coordinate it all, DAC (Digital to Analog Converter) and a suitable amplifier to drive the actual speakers. And that amplifier very likely needs more than the 5V coming over USB C so you need some sort of DC-DC boost converter that is dead silent and stable so it plays the transients clearly. Getting this all right in such a constrained space is possible, but as all things analog it requires some serious engineering and not just a "we throw that one good chip on and we'll be good". IMO you still fare better by getting decent cans and even a cheap USB soundcard like the Behringer UMC series.

liminalsunset 4y ago

Given this came out in 2019, notably absent is any mention of Bluetooth LE Audio, Bluetooth 5.2, and the new LC3 codec, which may resolve some of the problems mentioned here.

rasz 4y ago
LC3 will certainly resolve any potential Fraunhofer funding issues. Another patent encumbered codec when we could have settled on OPUS.
- liminalsunset 4y ago
  I was under the impression that it was LC3plus, not LC3, that was encumbered. The LC3 codec appears to be part of the open Bluetooth specification, and its role in replacing the former "free to implement" SBC appears to suggest this. Supposedly, I have read somewhere that LC3 uses some similar methods to Opus, and bears some form of technical resemblance (and hence inherits the benefits of) Opus. I have heard of someone I know using Opus directly to do some form of proprietary wireless low latency audio transmission, so it might actually be feasible, though it was noted that Opus decoding consumed a lot of microcontroller resources, which may be the real driver behind developing a "low complexity" codec.