Bluetooth stereo headphones

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Hw - 13 Dec 2003 02:13 GMT

Anyone know of a retailer with Bluetooth stereo headphones to listen to my
IPAQ5555 mp3's?

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Mitch_A - 13 Dec 2003 04:51 GMT

I've been looking high n low for a few weeks for such a product but so far
not a single whisper of anything. Could it be a BT bandwidth limitation or
other BT technical issue why no one has anything out yet?

Mitch

> Anyone know of a retailer with Bluetooth stereo headphones to listen to my
> IPAQ5555 mp3's?

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Alex Feinman [MVP] - 13 Dec 2003 05:06 GMT

To the best of my knowledge BT Headset profile uses 2 voice channels 64kbps
each, which means (Nyquist Theorem,
http://www.digital-recordings.com/publ/pubneq.html) that it cannot possibly
transmit frequencies over 8KBytes/sec / 2 4 KHz at 8 bit per sample - way
too low for quality music listening. I guess if someone would figure out a
way to use the data channel (over 700 Kbps), that would be enough for stereo
transmission for up to 48 KHz, but that would require using a different
profile - and phone stack might simply not support it

> I've been looking high n low for a few weeks for such a product but so far
> not a single whisper of anything. Could it be a BT bandwidth limitation or
[quoted text clipped - 4 lines]
> > Anyone know of a retailer with Bluetooth stereo headphones to listen to my
> > IPAQ5555 mp3's?

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[user5450] - 13 Dec 2003 16:11 GMT

> To the best of my knowledge BT Headset profile uses 2 voice channels
> 64kbps each, which means (Nyquist Theorem,
[quoted text clipped - 5 lines]
> would require using a different profile - and phone stack might
> simply not support it

Today?s standard CD quality (44.1 kHz 16 bit Stereo) audio requires
1411.2 kbps bandwidth in the transmission medium. The highest
bitrate achievable over Bluetooth is 721Kbps. Bluetooth solves
this problem by mandating the use of a royalty-free low-complexity
Subband Codec (SBC) originally developed by Philips. This ensures that
player will compress the CD-quality-stereo file into a size that fits into
the Bluetooth bandwidth, and the headphone or speaker on the other
side decompresses the streamed audio before playing out to the speaker.

~~~

Neat !!!!

Taken From:

http://www.impulsesoft.com/HomePage/products/headphone_reference.html

http://www.impulsesoft.com/HomePage/btaudioguide.pdf

http://www.impulsesoft.com/HomePage/products/iwish.pdf

if anyone finds these actually available for sale in the UK (or anywhere else
for that matter) I would really, really like to hear aout it :-)

[user5450]

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Alex Feinman [MVP] - 13 Dec 2003 19:19 GMT

Thank you for correcting my math.
The iWISH stuff looks interesting, but my point is still valid - this will
require at least a new BT stack implementation

> > To the best of my knowledge BT Headset profile uses 2 voice channels
> > 64kbps each, which means (Nyquist Theorem,
[quoted text clipped - 31 lines]
>
> [user5450]

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Fred - 13 Dec 2003 14:32 GMT

Right now, nothing really out there.

I think it may be a while before BT pocketpcs will really be able to use a
stereo headset for music. None out there so far.

Some BT headsets may be ok for audiobooks and gaming, but that's it.

I am also interested in BT for stereo headsets, but I assume it will be a
year or more before one really becomes available. Then you would need
drivers for the pocketpcs, which will be longer to come, if at all.

> Anyone know of a retailer with Bluetooth stereo headphones to listen to my
> IPAQ5555 mp3's?

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