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Can lossless audio be transfered via bluetooth?

Started by AnVo 4 months ago4 replieslatest reply 4 months ago115 views

Hi everyone,

I have a question that is that possible to wirelessly transfer lossless audio via Bluetooth?

Please help me explain technical reasons behind it such as the size of the the lossless data, the maximum data rate of Bluetooth, or the delay of the wireless transmission.

If no, what aspects would we improve to be able to wirelessly transfer lossless audio via Bluetooth?

Thank you very much.

Best regards,

An

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Reply by lamabrewJune 1, 2021

Sure, if your audio (data) is at a low enough sample rate, the answer is a resounding yes.  (8 bit audio at 8 kHz - no problem)...but that's probably not the answer you wanted.

There's two ways to look at this, theoretical and practical.  I'm going to assume the audio is stereo, 48 kHz, 16 bit, which is a (approx) 1.5 MBit/sec stream.

In BT 5 a new data rate was added, 2M bit/sec (vs. 1 M bit/sec previously).  But that's just the rate that the baseband data could theoretically be moved at. So theoretically the answer to your question is yes.

In practical terms though the achievable throughput in real world use due to finite Tx power, interference, and other BT and WiFi devices all fighting for the same channels, you'll maybe get half that theoretical amount.

So the answer to your question is no.

We could encode losslessly with FLAC, which will on average gets 50% reduction.  So the answer is maybe, at least over shorter distances and not too much RF crowding.

Though if we allow psycho-acoustically lossless compression (i.e. a panel of expert listeners in an idealized standard environment can not tell the difference between the source and the encoded material in a statistically valid test) then the data rate drops to the range of 300 kbit/sec for AAC (non standard) and 200 kbit/sec for the newer LC3 audio codec used as the default for BLE audio. I did not include the older SBC compression as it's questionable to say that even at its highest supported bit rate it would classify as sycho-acoustically lossless.

That 200 - 300 kbit/sec bit rate for psycho-acoustically lossless compression is achievable in the real world with the existing 1M bit/sec PHY speed.  So the answer to your question is yes.

Regards,

Brewster

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Reply by AnVoJune 1, 2021

Hi Brewster,

I really thank you for your useful information. This gives me a good overview to start researching on it.

Best regards,

An.

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Reply by lamabrewJune 2, 2021

Hi An,

No problem.  

I wrote that a bit tongue-in-cheek, i.e. gave you answers of No, Maybe, and Yes, all perfectly correct in response to your question as stated.

I like to (subtly...) encourage people to make sure they ask the right questions. I've seen a lot of companies spend a lot of time and money to answer the wrong ones.

In all seriousness though take a look at the new BLE Audio specifications.  There are huge changes to the way audio is handled in Bluetooth 5 and I expect by year end hardware supporting that will start showing up on the market.

Search for BLE isochronous audio.

Regards,

Brewster

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Reply by artmezJune 1, 2021

Add the APE format to the list of lossless codecs. I just saw some recent Bluetooth offerings from China that support that, and WAV and the aforementioned FLAC format. But, it's not always simply the format, but the throughput issue. Newer Bluetooth formats support (e.g. 5.0) support faster rates, but older ones like 2.1 and 2.3 don't have the bandwidth. Bluetooth, to my understanding, is a data transport protocol, or rather a collection of them, depending on version, whose throughput varies with version. Also, it uses the same ISM band as other wireless protocols, like proprietary HID (e.g. 2.4GHz mouse), Zigbee, etc. and that can reduce throughput when there is competition for the band.