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I understand why Bluetooth has issues with latency, but what is unclear to me is why we're still using lossy compression codecs for it. The latest state-of-the-art (at least according to the marketing department) is aptX-HD, which totally doesn't make sense to me. It's still lossy, yet instead of trying to get closer to lossless it rather adds 24-bit sounds which is, for the most part, useless to the consumer.

Meanwhile, full CD-quality sound uses about 176KBytes/s (or about 1.5MBit/s) which is well within reach of modern Bluetooth speeds. Why doesn't anyone do that, which, I think, would be much more meaningful for sound quality.

Vilx-
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  • At what level of losslessness does sound quality come good for you? – Andy aka Mar 06 '20 at 11:46
  • @Andyaka - Well, OK, you got me. I can't distinguish between a 256kbit MP3 and a CD. Still, I'm curious as to why we still jump through all these compression/decompression hoops, when it seems that they are completely unnecessary. – Vilx- Mar 06 '20 at 13:42
  • There are two reasons for this. (1) Latency which admittedly is not significant today. (2) Data / File size: If the errors are small enough that you can't tell the difference then why waste bandwidth? I suspect this question may be closed soon as opinion. – Warren Hill Mar 06 '20 at 16:15
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    Bluetooth shares its bandwidth with other Bluetooth devices. If two people are standing next to each other then there is only half the bandwidth. If there are three people then there is one third the bandwidth. In a public place like a bus or a plane, you will find lots of people using Bluetooth. If you need high bandwidth you will get degraded sound quality quickly. If you need as little bandwidths as possible then more people can coexist befor quality becomes an issue. – vini_i Mar 06 '20 at 16:19
  • @vini_i - care to make that an answer before the question is closed? :) – Vilx- Mar 06 '20 at 19:24
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    _" adds 24-bit sounds which is, for the most part, useless to the consumer."_ - it's all about marketing. Everybody know more bits are better, right? I mean, CD audio (which was invented way back in 1980) is 'only' 16 bit! – Bruce Abbott Mar 07 '20 at 00:32

2 Answers2

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One of the primary targets of the Bluetooth specifications is low power (small battery) and physically tiny devices. Bandwidth beyond that perceivable by the user (via very small audio transducers) wastes RF transmitter and receiver battery power. Compression reduces the required bandwidth. What is considered perceivable is usually measured by A/B user testing, not by theoretical quantization noise metrics.

So, at least in part, it's likely a marketable audio quality versus battery life trade-off.

hotpaw2
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  • But compression needs processing power which increases battery demands. Does the increased bandwidth really use more energy than is needed to compress the sound? – Vilx- Mar 06 '20 at 20:11
  • That sounds like a good separate question (e.g. not something to be answered in a comment). – hotpaw2 Mar 06 '20 at 21:57
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Bluetooth shares its bandwidth with other Bluetooth devices. If two people are standing next to each other then there is only half the bandwidth. If there are three people then there is one third the bandwidth. In a public place like a bus or a plane, you will find lots of people using Bluetooth. If you need high bandwidth you will get degraded sound quality quickly. If you need as little bandwidths as possible then more people can coexist before quality becomes an issue.

On a side note, an inexperienced IT person in my office ordered everyone Bluetooth keyboards and mice (12 people). Hilarity ensued. There was not enough bandwidth for everyone. Keyboards wouldn't type and then all the text would appear all of a sudden. Mice wouldn't move and then move all of a sudden. Not sure if anyone tried to listen to music at the same time. They ended up being used for less than a week.

vini_i
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  • 12 keyboards and 12 mice did that? Really? In my office I can think of at least 4 people who use bluetooth headphones for listening music (and there's an effort to get headphones for even more people), as well as some bluetooth mice I think, but we haven't had any issues yet... – Vilx- Mar 06 '20 at 20:13
  • @Vilx- It also depends on the distance and obstructions. Bluetooth is very short range. This was a medium-sized room with all the people in it open office style. Cubicle walls might have helped. I would be mindful of too many Bluetooth devices in a small area. – vini_i Mar 06 '20 at 20:17
  • Ours is an open office too and people are pretty close. I can see what the range of headphones is on Monday, but I suspect that they will reach everywhere. – Vilx- Mar 06 '20 at 21:06