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Why does Bluetooth audio transmission must use compression?

sarumbear

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The CD quality (44.1kHz/16-bit) audio data rate is 1.4Mb/s. The common Bluetooth v2 protocol is specified to be able to carry data at the rate of 2Mb/s. Then why does BT audio is always compressed?
 

litemotiv

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I suspect this is because BT has limited transmission power, so the maximum rate will drop quickly once you are a few meters away.
 
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sarumbear

sarumbear

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I read that as; we realised that lossless audio is a USP so we added that to our new HP chips. There never was a technological limitation. It’s the same BT protocol and the same AptX codec. They allowed it to scale to mathematically lossless.

So the answer to my question was, there was no demand till now. The year 2021 saw big streaming players to offer and hence advertise lossless. Chip suppliers responding to that.
 

TurtlePaul

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Bluetooth is a multi-device bus. First priority for device makers is that you Bluetooth mouse, keyboard, headset and car connection can all work simultaneously on one device. 80% of the bandwidth for better audio wasn’t the priority.
 

escksu

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The CD quality (44.1kHz/16-bit) audio data rate is 1.4Mb/s. The common Bluetooth v2 protocol is specified to be able to carry data at the rate of 2Mb/s. Then why does BT audio is always compressed?

Another thing we need to take note is that bluetooth is half-duplex and its serial. This means when it is sending data, it cannot receive. Also, it can only send data to 1 device at any time (quick switching give the sense that its simultaneous). And then, there is protocol overhead as well.

As others have also em tioned, 2mbps oa max speed under optimum condition.
 
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sarumbear

sarumbear

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Bluetooth is a multi-device bus. First priority for device makers is that you Bluetooth mouse, keyboard, headset and car connection can all work simultaneously on one device. 80% of the bandwidth for better audio wasn’t the priority.
I agree that it’s a multiuser device but you use neither the headset nor the car while listening on headphones, and neither mouse nor keyboard requires any comparable bandwidth. The codec AptX is designed to be adaptive, why not make the top end lossless from the start? However, it looks like, and as you said, “better audio was not priority”. Even though the market was full of higher and higher quality wireless headphones and speakers and every Hi-Fi magazine was full of reviews.

It looks like Qualcomm had been sleeping. A very typical behaviour when you own the market.
 
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sarumbear

sarumbear

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Another thing we need to take note is that bluetooth is half-duplex and its serial. This means when it is sending data, it cannot receive. Also, it can only send data to 1 device at any time (quick switching give the sense that its simultaneous). And then, there is protocol overhead as well.

As others have also em tioned, 2mbps oa max speed under optimum condition.
The fact is even though none of those limitations have changed Qualcomm is now offering lossless.
 

GaryH

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I read that as; we realised that lossless audio is a USP so we added that to our new HP chips. There never was a technological limitation. It’s the same BT protocol and the same AptX codec. They allowed it to scale to mathematically lossless.

So the answer to my question was, there was no demand till now. The year 2021 saw big streaming players to offer and hence advertise lossless. Chip suppliers responding to that.
I don't think it's as simple as that. I suspect achieving the below involved considerable technological challenges:
these technologies deliver rates beyond 1Mbit/s yet smoothly scale down to 140kbits/s in congested RF environments to minimize any audio dropouts or glitches for a consistent and reliable listening experience
 
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sarumbear

sarumbear

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I don't think it's as simple as that. I suspect achieving the below involved considerable technological challenges:
But AptX was designed to adapt compression. We are talking the top end limit only. The sliding compression is already baked in the design spec.
 
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sarumbear

sarumbear

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Which is the end that is most likely to suffer from dropouts and glitches due to the presence of other RF signals.
Why are they introducing lossless then? To help manufacturers produce equipment which drops out sound?
 

GaryH

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Why are they introducing lossless then? To help manufacturers produce equipment which drops out sound?
Which is the end that is most likely to suffer from dropouts and glitches due to the presence of other RF signals*
* - an issue Qualcomm have (claimed) to have now solved (or at least minimised) by optimizing the codec.
 

Blackdog

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Why use BT at all for audio?
For the car primarily, and for use with cell phones. Anything else should be using wifi. BT range is limited and for good reason. This eliminates conflicts with other devices.
It's interesting to me that BT is used at all. It started life as a machine control system for industry, but was so badly plagued by drop outs, and interference it never caught on. A lot of the flaws are still present, but things have improved.
 
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sarumbear

sarumbear

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* - an issue Qualcomm have (claimed) to have now solved (or at least minimised) by optimizing the codec.
Source?
 

Chrispy

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For the car primarily, and for use with cell phones. Anything else should be using wifi. BT range is limited and for good reason. This eliminates conflicts with other devices.
It's interesting to me that BT is used at all. It started life as a machine control system for industry, but was so badly plagued by drop outs, and interference it never caught on. A lot of the flaws are still present, but things have improved.
Yes, that's a better use scenario, only place I'll use BT in the car and then lossless really doesn't matter anyways. I prefer a thumb drive in the car and then can use either lossless or lossy depending on memory size...but the lossless isn't an advantage. Around the house wifi is far better than BT in fidelity and range, so I just don't use it in the house at all.
 
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