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[jacobacci]

One of my MC21 installs is on my Lenovo T430 laptop, which has a Bluetooth 4.0 transmitter. At the receiving end I have a Philips AEA2700 BT adapter http://www.p4c.philips.com/cgi-bin/dcbint/cpindex.pl?slg=en&scy=hu&ctn=AEA2700/12 which can decode aptx and aac natively.
The music on my laptop is m4a @320kbit/s, which sounds transparent to my ears for casual listening.
Is there anything I need to configure in MC21 in order to stream the aac files natively to the BT receiver and have them decoded there? Or will they get decoded by MC21 and then reencoded to aac when I stream them to the AEA2700?

[blgentry]

As I understand it, no bluetooth transmitters do any kind of "passhthrough" or "bitstreaming".  Bluetooth defines it's own transport, which is normally SBC, the lower quality bluetooth audio that every BT transmitter and receiver supports.

I just did a little research on aptx, and it looks like it's only supported by a handful of BT devices.  For example, only one notebook is listed on the aptx site as being a supported sender/receiver:

http://www.aptx.com/category/notebooks

As far as I can tell this is what will happen:

AAC goes into MC.  MC decodes to PCM internally.
PCM is passed to the driver for your laptop's BT transmitter.
The BT transmitter decides how to send it to the receiver based on the initial handshake with the receiver.  For almost every BT transmitter this is going to be relatively low quality SBC coding.  aptx or AAC would only be used if both BT sender and receiver both supported it.

I think you're going to end up with "regular old BT" audio quality with this setup.  Which might be perfectly fine depending on your playback equipment and how you will use it.

Brian.

[jacobacci]

Hi Brian
thanks for the info. I have googled this subject for quite a while but I have found very little information about how BT actually uses other codecs than SBC.
Apparenty iOS has aac built into its bluetooth stack and I found some threads saying that an aac file on the iPhone would not be decoded / reencoded. But it was all very vague.

[blgentry]

I'll admit to not having a whole lot of knowledge on this subject myself.    I've done a little bit of research and that's about it.  I consider bluetooth *overall* to be a "casual use" solution.  It has limited range and (generally) limited audio quality.  It's good for some things and not so good for others.  In a car, with a basic stereo, it's probably a good solution.  At home, with nice headphones or nice speakers, I'd be looking for a different solution.  At home for listening while doing other stuff (casual listening) it might be a good solution.  Depending on how close the BT sender is going t be to the receiver.

I'm sure you knew most of this. 

Brian.