What's the difference between stereo and hands free?
https://superuser.com/questions/1088942/whats-the-difference-between-stereo-and-hands-free
the "Stereo" device is the main high-quality playback device of the headset, while the "hands-free" device is a lower quality monophonic playback device
The "Stereo" device is technically known in Bluetooth jargon as "Advanced Audio Distribution Profile", or with an acronym A2DP. It is optimized for transferring 2-channel stereo sound with good quality in one direction only.
HSP profile, are designed to minimize the processing power requirements.
めも、未検証
