[HN Gopher] Audio over Bluetooth: most detailed information abou...
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Audio over Bluetooth: most detailed information about profiles and
codecs (2019)
Author : schaum
Score : 49 points
Date : 2021-03-06 16:37 UTC (6 hours ago)
(HTM) web link (habr.com)
(TXT) w3m dump (habr.com)
| Fannon wrote:
| I wonder how the new Bluetooth LE Audio with the new LC3 codec
| would fare in this comparison.
|
| See https://www.bluetooth.com/learn-about-bluetooth/recent-
| enhan...
|
| There's on thing in the current state of bluetooth audio that
| actually bugs me: Once you use a microphone, the audio quality
| significantly degrades from the usually stereo audio quality
| (which is good enough for me).
|
| I'm curious when we'll see LE Audio in broad adoption and how
| much of an improvement it will actually be.
| ValdikSS wrote:
| It's still not clear whether LE Audio supports high quality
| duplex audio. They say you can use it for microphone, but that
| doesn't certainly means voice communication (both listening and
| speaking at the same time).
| samstave wrote:
| Might be a lame question, but can BlueTooth connections be
| intercepted and "heard" ?
|
| If so, How?
| elitepleb wrote:
| You just get some hardware that can monitor the traffic like
| greatscottgadget's ubertooth one.
|
| As for recreating the audio, you'd have to deal with capturing
| the key exchange handshake and cracking it.
| SwaraLink wrote:
| Bluetooth has the Secure Simple Pairing (SSP) feature, and
| Bluetooth Low Energy has the LE Secure Connections feature,
| which both use Elliptic Curve Diffie-Hellman Key Exchange and
| therefore is protected against passive eavesdropping. The
| standard also includes the ability to support authenticated
| pairing for protection against Man-in-the-Middle attacks; if
| you've ever had to see if a 6-digit number matches on the two
| devices that are being paired, then you are seeing the
| authenticated pairing taking place.
|
| Even though the Bluetooth standard includes these features,
| many products don't actually use them and simply transmit data
| without any encryption or authentication procedure. This is
| particularly a problem with many Bluetooth LE products.
| tgsovlerkhgsel wrote:
| Bluetooth supports solid encryption once paired, but the
| pairing is usually unauthenticated and thus subject to man-in-
| the-middle attacks.
|
| Whether the encryption is implemented correctly and on (with
| strong enough keys) by default on most devices is another
| question of course.
| perlpimp wrote:
| Upon coming up on sound guys article it became apparent why Apple
| has cut the cord. Their compression is top notch - I have
| experimented with various bt headsets/headphone/bt-amps. Apple
| AAC implementation keeps layering and detail much more compared
| to AptX HD counterparts - using same devices across the range.
| wombatmobile wrote:
| > Unfortunately, as of 2019, the quality of voice transmission
| via Bluetooth is still poor, and it is not clear why Bluetooth
| SIG is not doing anything about it.
|
| I would speculate there is no party with a strong interest in
| voice only communications participating in the Bluetooth SIG.
|
| That's because the biggest industry group for voice only
| communications has its own wireless standard, DECT.
|
| I've been trying to find a way to pair bluetooth hearing aids
| with a DECT landline phone but as far as I can see, no landline
| phone manufacturer has implemented Bluetooth Hands Free Protocol
| to work with hearing aids. This surprised me.
|
| My 89 year old mother's hearing aids can pair with iPhone and
| Android, but she doesn't use a mobile device so I need it to pair
| with an ordinary DECT landline phone. I understand both landlines
| and old people are declining markets.
|
| Anyway, to confirm this blank I had to peruse a lot of DECT and
| Bluetooth standards. Bluetooth Profile Specifications and
| compliance therewith are a rabbit hole, difficult to navigate
| because DECT phone device manufacturers don't publish
| capabilities.
| jnsie wrote:
| I have been searching in vain for a Bluetooth transmitter that
| can transmit from my tv to 2 Bluetooth headsets and supports
| Dolby surround (so that I don't have to switch my TV to PCM every
| single time I switch to headphones). So frustrating
| sgtnoodle wrote:
| This seems like something that could be done easily in the
| analog domain. Most TVs have a 3.5mm or RCA line-out, line-in
| to bluetooth adapters are cheap, and analog signals can be
| fanned out with a passive splitter.
|
| In practice, the conversion to analog and back shouldn't have
| any noticable effect. The bluetooth adapter is going to
| compress the stream anyway.
|
| Depending on what you're hoping for, though, bluetooth might
| have too much latency. Media players on mobile devices and PCs
| are aware of the fact that they're outputting to a bluetooth
| audio device and compensate for it by delaying the video as
| well.
| amelius wrote:
| Why can't Bluetooth pair with more than one audio sink at the
| same time? I mean, watching a movie on a laptop with a friend is
| not a strange requirement, is it?
| akvadrako wrote:
| It can with BT5.
| wombatmobile wrote:
| Taotronics Bluetooth 5.0 transmitter/receiver supports two
| headphones.
|
| Marketing information from Amazon
|
| LOW DELAY: Low Latency for High-fidelity Stereo Sound, lag-free
| content streaming in transmitter mode. Low Latency supported
| Bluetooth receiver is required
|
| MAKE IT TWO: Upgraded 2-in-1 Bluetooth V5.0 transmitter can be
| paired with two Bluetooth receivers (like headphones +
| speakers) simultaneously. Note: Low Latency does NOT support
| Dual Link mode
| baybal2 wrote:
| It can, it's just the non-lunux userspace cannot.
|
| The problem is the fine synchronisation - possible to do with a
| lot of effort in current linux stack, but most commercial
| vendors just turn it off because they don't want to bother.
| amelius wrote:
| Why don't these vendors lose the certification then?
| baybal2 wrote:
| I think it just never been a part of it.
|
| Only hardware is BT SIG certified I believe, not userspace
| software.
| rektide wrote:
| Bluetooth LE Sharing was announced a year ago[1], that is for
| broadcasting to multiple receivers. There's no (nearly no?)
| products for it yet. It is fairly low bitrate & has some fresh
| new codec specifically for it, I believe.
|
| I really wish wifi had some standards for this sort of stuff
| too.
|
| [1] https://www.bluetooth.com/bluetooth-resources/introducing-
| bl...
| inetsee wrote:
| This may not be exactly what you are asking for ... but a
| search on Amazon for "bluetooth transmitter 2 devices" turns up
| several devices. I'm using it with a TV, but I don't see why
| the transmitter couldn't be plugged into the audio out on a
| laptop to send the audio to two devices.
| twistedcheeslet wrote:
| For a complete Bluetooth layman like myself, this was a
| fascinating read.
|
| Alongside god and the manufacturer, I now know to curse the
| standards body too whenever trying to connect these damn
| headphones!
| amelius wrote:
| Can't we just replace this standard by WiFi? That would be one
| less standard to deal with. And much better bandwidth.
| iancmceachern wrote:
| Too much power for small devices like earbuds or iot devices.
| sgtnoodle wrote:
| I imagine that power consumption is proportional to amount of
| data and inversely proportional to latency and data rate. To
| minimize latency, the transmitting device needs to send
| smaller packets more often, leading to poor efficiency due to
| overhead. The faster each packet can be sent, though, the
| less time the transmitter needs to be powered on.
|
| I suspect that the only difference in power consumption would
| be due to the modulations that wifi uses vs. bluetooth, i.e.
| wifi is able to cram more bits into the same amount of RF
| energy.
|
| The tricky bit with radio comms is that you absolutely have
| to be able to cope with data loss. The easiest, lowest
| latency way is to just encode the data in a way that allows
| it to degrade gracefully. The listener is aware of the data
| loss, but isn't bothered by it. This implies that there's a
| lot of redundant information in the data. That is at odds
| with compression, though, because compression is all about
| removing redundant information; a loss of any bit of data
| results in severe degradation. Radio links that send
| compressed streams of data need to either rely on
| acknowledgements with retransmission on data loss, or they
| need to add just enough redundant information for the
| receiver to reconstruct the original data stream even after
| expected packet loss. The algorithms that provide that
| "forward error correction" work by distributing redundant
| information across multiple packets, which inherently adds
| latency since the receiver needs multiple packets to decode
| (or recreate) the payload of single packets.
| amelius wrote:
| That depends on how long you want to use them. For some the
| trade-off against sound quality, features and user-
| friendliness might be favorable.
| rektide wrote:
| the shield tv's controller (2015) was wifi based, & could
| transit audio. it's not tiny, but it shows wifi was viable
| for a latency-sensitive battery-powered system five years
| ago. for many headsets i'd think it would be quite doable but
| yes i'm not sure we've scaled wifi down to earbud sized
| devices. and yes power consumption is afaik higher.
|
| it feels mainly like an adoption / standardization problem.
| we have chromecast speakers galore & wow is it nice having
| devices available over the network. alas there's no
| standardizations, no cooperation, no system for wifi to be
| useful. other than the very limited controlled & closed ones.
| iancmceachern wrote:
| That controller had a 2600 mah battery for ~60 hours of
| operation. Much larger in power capacity and volume than
| what is suitable for tiny earbud like devices.
| https://batteriesglobal.com/products/nvidia-shield-
| battery?v...
| rektide wrote:
| Ok so 260 mah for 6 hours? Using some 5 year not-that-
| fancy-at-the-time old technology (Ozmo2000)? That does
| far far far far more than send audio? That is much lower-
| latency than what we'd need to compete with Bluetooth
| (which radically increases wireless power needs)? For
| comparison, Google Buds are 120 mah & 5 hours. All we
| need is a 2x improvement in power, for a far less complex
| device, & we've had 5 years? You are making the case for
| me my man. This sounds more doable than I thought!!
|
| Miniaturization is indeed a challenge. Who does make
| really small wifi units? Who do they sell to? How much
| smaller do they need to be? I suspect it's simply never
| been a goal. And why would it be? There's no protocols
| that make wifi even potentially compatible with these
| sort of consumer device systems, no matter the size! Even
| with what we have today though, a wifi microphone or wifi
| gaming headset should be easily possible, no challenge at
| all, and could have far better quality & likely latency
| than what we expect from bluetooth. And I rather believe
| we could make smaller wifi if we had an interest in doing
| so. We are limited by our imaginations, our imaginations
| and our lack of standards/will.
| neolog wrote:
| Wi-LE (low energy)
| https://dl.acm.org/doi/10.1145/3365609.3365853
| amelius wrote:
| That's interesting.
|
| > Surprisingly, Bluetooth devices require nearly three
| times as much energy to transmit a bit of data at the
| physical layer than WiFi devices.
| Rebelgecko wrote:
| Would latency be comparable?
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(page generated 2021-03-06 23:02 UTC)