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

sajunky

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You forgot to mention that Opus degrades gracefully in the face of packet loss and can change bitrate dynamically without any glitching. One could not dream of a better codec for wireless transmission. I would kill for the Bluetooth industry to support Opus, but it doesn't look like anyone cares. (Or maybe it's just too computationally intensive, I don't know.)
Actually SBC codec automatically adjust a quality according to the transmission speed, unlike aptX, etc... It is generally not known, as a standard SBC rate is fixed, but if you force a double speed, SBC quality becomes very close to the original. Tests were made on Linux PC with modified Bluetooth parameters that shows we actually do not need another codec. It is even more: one of the certification requirement for devices is that sink device should accept negotiation requests of much higher SBC rate (I don't have a figure right now). It is simply a current Bluetooth implementation that arbitrary limit SBC transmission speed.
 

edechamps

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Actually SBC codec automatically adjust a quality according to the transmission speed, unlike aptX, etc...

I just know that when I use SBC between Windows 10 and Bose QC35, I can hear glitches during packet loss and/or changes in SBC parameters. Opus is specifically designed to hide these as much as possible.
 

sajunky

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I just know that when I use SBC between Windows 10 and Bose QC35, I can hear glitches during packet loss and/or changes in SBC parameters. Opus is specifically designed to hide these as much as possible.
You hear glitches during packet loss, thats all. They is no way any other codec would hide packet loss. Configuration changes glitches in SBC? I never heard about.
 

Occamsrazor

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Are there any Bluetooth dongles/transmitters that support LDAC? I'm talking a device that plugs into a computer or DAC and transmits LDAC bluetooth to LDAC-supporting bluetooth headphones?
 

Degru

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Are there any Bluetooth dongles/transmitters that support LDAC? I'm talking a device that plugs into a computer or DAC and transmits LDAC bluetooth to LDAC-supporting bluetooth headphones?
Shanling M0 is able to do this though I think latency is not great. It also can receive LDAC and output to a USB DAC.
 

Occamsrazor

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Shanling M0 is able to do this though I think latency is not great. It also can receive LDAC and output to a USB DAC.

I have no personal experience but from what I’ve read it can only transmit LDAC when used as a DAP, not with USB input.
 

Degru

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I have no personal experience but from what I’ve read it can only transmit LDAC when used as a DAP, not with USB input.
No, this is one of the functions they added in a recent firmware update. You connect to the headphones/receiver first with LDAC, then you plug it into computer USB. For LDAC->m0->DAC you plug the DAC in first then connect the Bluetooth.
 

mykeldg

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is there an LDAC BT adpater already that can be plugged into computers to use it as a transmitter?(windows laptop/pc)
 

klaberte

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You hear glitches during packet loss, thats all. They is no way any other codec would hide packet loss. Configuration changes glitches in SBC? I never heard about.

I just happened to have made a study of SBC, how it works, how it can be improved, etc. and wrote the following article.

https://docs.google.com/document/d/1YPTwFhvo99suyrwkT4Z97so9_xwoOGkpSqgveLpYvYc/edit?usp=sharing

There are several internal parameters that get negotiated at connection time, which, if set properly, could improve fidelity by increasing the overall bitrate. I've also created audio files so that you can judge for yourself (link to audio samples is in the article).

One of the important conclusions is that, if the source (SRC) negotiated the connection more wisely, SBC can improve audio fidelity *without making changes to the sink (SNK)*, which means it should work on the huge majority of legacy speakers, headsets, etc.
 
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somebodyelse

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Thanks for the info @klaberte. From a quick look it reminds me of this article which resulted in changes to SBC negotiation in some of the community android distros, and a patch set for PulseAudio. I'll have to give it a more in depth read.
 

klaberte

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Thanks for the info @klaberte. From a quick look it reminds me of this article which resulted in changes to SBC negotiation in some of the community android distros, and a patch set for PulseAudio. I'll have to give it a more in depth read.

Yes, ValdikSS (who wrote your cited article) and I have been in touch and s/he kindly reviewed the article last week. I also credit him in the acknowledgements for being the inspiration for my suggestion to set nrof_subbands to 4. You will find more references to his work and tools in my article.
 
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