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bluetooth and wifi streaming is it lossless?
airtas
post Dec 5 2010, 16:15
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I am assuming bluetooth headphones are lossy or any bluetooth stream but wifi media sharing is not.

I am only assuming though, can someone confirm?
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airtas
post Dec 7 2010, 04:37
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so a v0 mp3 is technically transcoded to a file less than 3mb via a2dp?
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SebastianG
post Dec 7 2010, 12:06
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QUOTE (airtas @ Dec 7 2010, 04:37) *
so a v0 mp3 is technically transcoded

Not necessarily. It's theoretically possible to send mp3 data directly to an A2DP sink. This requires an A2DP source that has access to the original MP3 data and is able to send it directly and a sink that supports MP3.

QUOTE (airtas @ Dec 7 2010, 04:37) *
to a file

I don't think that intermediate files are involved. More like "on-the-fly conversion".

QUOTE (airtas @ Dec 7 2010, 04:37) *
less than 3mb via a2dp?

Bluetooth 1 is limited to 1 megabit/s = 1000 kilobits/s. Bluetooth 2.1 is limited to 3 megabits/s = 3000 kilobits/s. Keep in mind that "/s" means "per second". Your MP3 files have at most a bitrate of 320 kilobits per second.

This post has been edited by SebastianG: Dec 7 2010, 12:08
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Arnold B. Kruege...
post Dec 7 2010, 13:54
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QUOTE (SebastianG @ Dec 7 2010, 06:06) *
QUOTE (airtas @ Dec 7 2010, 04:37) *
so a v0 mp3 is technically transcoded

Not necessarily. It's theoretically possible to send mp3 data directly to an A2DP sink. This requires an A2DP source that has access to the original MP3 data and is able to send it directly and a sink that supports MP3.


That's all quite idealistic, but in the real world, probability = zero or very close to it.

It is hghly probable that music files in *any* format are transcoded for transmission over the Bluetooth link. To do otherwise (except use an uncompressed audio format) would require the addition of file format support to the reciever which would make it more complex and therefore larger and more power-intensive.

According to the official Bluetooth SIG site:

Official Bluetooh web site statement about audio transmission

Audio

"In the air-interface, either a 64 kb/s log PCM (Pulse Code Modulation) format (A-law or μ-law) may be used, or a 64 kb/s CVSD (Continuous Variable Slope Delta Modulation) may be used. The latter format applies an adaptive delta modulation algorithm with syllabic companding. The voice coding on the line interface is designed to have a quality equal to or better than the quality of 64 kb/s log PCM. The table below summarizes the voice coding schemes supported on the air interface."


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Roseval
post Dec 7 2010, 14:34
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QUOTE (Arnold B. Krueger @ Dec 7 2010, 14:54) *
In the air-interface, either a 64 kb/s log PCM (Pulse Code Modulation) format (A-law or μ-law) may be used, or a 64 kb/s CVSD (Continuous Variable Slope Delta Modulation) may be used.



This is probably Bluetooth Audio.
A2DP allows for a bit more than 64 kbs
http://www.bluetooth.com/English/Technolog...on_Profile.aspx


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Arnold B. Kruege...
post Dec 7 2010, 15:13
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QUOTE (Roseval @ Dec 7 2010, 08:34) *
QUOTE (Arnold B. Krueger @ Dec 7 2010, 14:54) *
In the air-interface, either a 64 kb/s log PCM (Pulse Code Modulation) format (A-law or μ-law) may be used, or a 64 kb/s CVSD (Continuous Variable Slope Delta Modulation) may be used.



This is probably Bluetooth Audio.
A2DP allows for a bit more than 64 kbs
http://www.bluetooth.com/English/Technolog...on_Profile.aspx


I tried to find a real-world implementation of this.

A likely candidate would seem to be the Sennheiser PX 210 BT

Link to Sennheiser PX 210 BT spec sheet

BTW, this requires the use of a Sennheiser BTD300I Self Powered Bluetooth Adapter or equivalent (optimal, extra).

At any rate the Sennehser PX 210 BT spec sheet says that is uses an audio encoding technique called APT-X. The APT-X web site seems to describe it as a lossy transmission technique and says something about transmitting audio at 64 kbps.

If it was my money on the line I'd skip the Bluetooth and put my bucks on the Sennehsier RS 170, or some such.

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Roseval
post Dec 7 2010, 16:07
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QUOTE (Arnold B. Krueger @ Dec 7 2010, 16:13) *


Have a look at MX W1, lossless (16/44) using KLEER
http://www.sennheiser.com/sennheiser/home_...less-headphones


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