Opus! It's a merge of a codec designed for speech (from Skype!) with one designed for high quality audio by Xiph (same people who made OGG/Vorbis).
Although it needs some more work on latency, it prefers to work on bigger frames but default than Bluetooth packets likes, but I've seen there's work on standardizing a version that fits Bluetooth. Google even has it implemented now on Pixel devices.
Fully free codec!
Nazi talk