Curses on you, bluetooth

Submitted by brad on Wed, 2006-01-11 19:20
Topic: 
Telecom

Well, I am going to get a bluetooth cell phone shortly and so I got a headset and dongle to use on my laptop, where I also make VoIP calls.

I was shocked, flabbergasted to find that the bluetooth headset profile only transmits audio at telephone quality 8khz sampling rate. So even plugged into my laptop for hifi (didn't think I
would ever need to use that term again) recording, it sounds like a telephone, and likewise for
playback.

Why? Why? Why?

This makes all the typical bluetooth headsets a terrible choice for Skype or other hifi voip, no good as voice recorders, terrible for listening to ordinary quality audio and effectively useless for anything but toll-quality phone calls.

It would have been so simple to have allowed the headset profile to support higher quality, or to simply have it always do high quality and let the cell phones do the trivial downsampling. I realize that an earpiece is not going to provide headphone quality but there's no reason it should always sound like crap.

Bluetooth includes a "headphone" profile that does CD quality digital audio, and that profile can in theory have microphone to make a hifi headset, but that's not what everybody is buying these days, so no point in making sofware products (such as VoIP tools) that use a bluetooth headset and want higher quality.

Perhaps a few years down the road it will be common to have headphone profile headsets but we are now a long way away from this.

What a stupid mistake. Sorry, but I just have to rant.

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Comments

Tom Limoncelli

Thu, 2006-01-12 16:43

A cell phone is 8khz. Normal land-line calls are 64khz (or 56khz depending on how you measure it)

brad

Thu, 2006-01-12 23:01

Nope. Phones sample 8,000 times/second (to get a frequency response of 4000 hz.) The samples are either 7 bits or 8 bits each, resulting in either 56kilobits or 64 kilobits of data per second, but still just 4000 hz of frequency response and 8khz sampling. That's where the 64 and 56 come from.

Tom Limoncelli

Fri, 2006-01-13 18:28

I stand corrected.

I was, however, once told that a cell phone call used less bandwidth than regular voice call and that a certain vendor was getting flack because with their equipment cell-to-cell calls were sent over old-style voice systems, thus wasting bandwidth.

brad

Fri, 2006-01-13 22:20

Correct, cell phones use various lower bandwidth codecs, which are compressed, and also lower frequency response.

airmon

Tue, 2006-01-17 09:42

I'm by no means a bluetooth expert, but IIRC, there's another bluetooth service for high fidelity audio that includes the ability to make and receive calls. I think it's called A2DP and some of the bluetooth phones have it, like the ones using windows smartphone 5.0.

After a little googling I found this link which tells more about it in some of the phones msmobiles.com and has some interesting screen captures.

brad

Tue, 2006-01-17 13:13

Yes, that's the stereo headphone profile I identify in the posting. Phones have little reason to use it for ordinary cellular calls which are worse than the 8khz sampling of the headset profile anyway. Some may support it to do music players, which is the possible salvation. But in the meantime, most headsets sold are useless except for phone calls.

nigel

Fri, 2007-12-07 04:41

I am trying to find Bluetooth headsets capable of hi quality voice transmission as well & I share your frustration.
Have you managed to find any in the last 11 months?

Nigel

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