there's a lot of bogus / outdated tweaks floating around the net for BT audio. The A2DP support in WM5 was very poor, and some crazy registry settings claimed to alleviate the problem.
Since WM6, the optimal settings are very different, so you have to make sure you haven't been following an older set of tweaks.
Here's the current recommended settings:
REMOVE ALL ENTRIES AT HKLM\Software\Microsoft\Bluetooth\A2DP\Settings
Except for this one:
UseJointStereo = 1
THIS IS THE ONLY NECESSARY SETTING FOR GOOD A2DP. What this does is enable Joint-Stereo for the SBC codec, which is important and makes the biggest significant change to improve sound quality. (Note: In earlier versions of WM5 and WM6, Joint-Stereo was broken and resulted in a mono-output. This is not the case anymore with the newer WM6 ROMS.)
Delete the bitpool settings! I can't stress this enough! they serve to limit the amount of bandwidth/CPU time dedicated to encoding the audio, which results in lower-quality sound, but frees up system resources for other tasks. This was necessary on slower CPUs (like the 200mhz omap), but you don't need it and all it will do is lower the quality.
For audiophiles, you can also optionally set:
Name: SampleRate
Value (DWORD): 48000 (decimal)
Default is 44000. This shouldn't make a great deal of difference, but trained ears might be able to tell. To be quite honest, I prefer the sound of 44000 often because it has a more forward-clarity. For complex instrumentals, 48000 will give wider range I think.
If you do this right, and have a decent stereo receiver, bluetooth audio can sound as good as wired headphones. I've plugged saunheisser earbuds into an a2dp receiver, and had audiophile friends swear they can't tell the difference.
