Or, the sound server/mixer in the phone could switch from MP3/AAC passthrough to mix-and-reecode whenever there are multiple streams, and switch back to passthrough once the music is the only remaining sound.
Sure, that's technically feasible, but since nobody cares about mp3 passthrough anymore there's no incentive to implement it.
FLAC and OPUS are royalty-free nowadays, and OPUS is even a IETF standard. Bluetooth should consider introducing them to Bluetooth...
That would make many people very happy. No idea what BT SIG is up to these days.
Trivially possible, but it would have required a MP3 *codec* core, instead of a purely MP3 decoding hardware core as done back then, which would have risen the cost of the SoC and thus of the feature phone.
You have a funny definition of "trivial".
Correct me, if I'm wrong, but 25Mpbs figure is basically using AMP - Alternative MAC/PHY. Or in other words, using Bluetooth over a 802.11 transport (i.e.: over a Wifi transport).
Nope, you're not wrong. That's what I get for skimming the results for latest BT specs. Regular Bluetooth EDR is more like 3Mbps -- the data rate is one order of magnitude greater than hi-fi audio, not two. I stand by my assertion that faster radios aren't needed for high-quality audio.