I read the A2DP spec once. I think I have it somewhere - I'll have to try to dig it up... It outlines the various codecs that can be used. As someone pointed out once, there really isn't enough bandwidth for it to -not- use some form of compressions as opposed to the uncompressed subband codec @ 723kbits/sec.


From the Wikipedia...

"It includes mandatory support for low complexity subband codec (SBC) and supports optionally: MPEG-1,2 Audio, MPEG-2,4 AAC and ATRAC."
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I am wondering if there is any reason to think the quality would be any better over Bluetooth than using an FM trasmitter with an iPod.
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Hi UUronL: Using theory I might understand, how do you respond to the issue raised below (mentioned above originally)?

"I am wondering if there is any reason to think the quality would be any better over Bluetooth than using an FM trasmitter with an iPod."

Your answer may be imbedded in what you say above, but you couldn't prove it by me. Thanks.
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It wouldn't use an analog signal modulated over a frequency band like products using the FM band would. Instead, it's an encoded, packetized digital signal over the carrier bands - similar to the difference between analog and digital cable TV. There are mechanisms within the decoding process that will hide errant data, and there are also provisions at a lower level (most likely some form of forward error correction) that should help mitigate most loss by sending more copies of the data than is actually necessary. This is common practice for such transmission mediums. That's why the spec calls for a maximum of 723kbits/sec for the SBC, and the max actual data rate is only 345kbit/sec.

Again though, I'm stronger on the networking side than the coding theory. Getting copies of the bits to the car is certainly important, but the coding and filtering processes are extensive - I can't really speak to the effects these might ultimately have on sound quality. If anyone can correct aspects of my understanding or explanations thus far, please chime in.

I would say that the potential appears to be there for good quality audio.
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Thanks much.

 

I tend to agree. The protocol to be used suggests bit for bit transfer with CRC checks. Still, hearing is believing.

 

or to really dumb it down surely the main difference is that FM tranmissions are compressed to accomodate bandwith restrictions and the BT link would send data at MP3 quality which whilst not CD Audio quality is significantly better than Fm Quality

 

Right, but the CRC won't trigger a retransmission, it will only invoke some kind of muting or replay of the previous block. However, I would expect FEC to prevent the majority of loss that might occur.

 

Awwww - ratfarts...

If these fools have it right, (and I'm not saying they do) - it would seem to indicate that a Bang and Olufson audio option is in the works for the 5 series that would include the Samsung phone with cradle as well as the bluetooth support for it. That could really mean all sorts of unique system components, although not necessarily.

http://www.mobilemag.com/content/100/340/C4964/