Thanks for the link, it is great consolidated reading! And this makes me : "AAC has many extensions to the standard encoding method. One of them—Scalable To Lossless (SLS)—is standardized for Bluetooth and allows you to transfer lossless audio. Unfortunately, no SLS support could be found on existing devices. An extension to reduce transmission delay AAC-LD (Low Delay) is not standardized for Bluetooth.", so much more could be had. "The situation with AAC is ambiguous: on one hand, theoretically, the codec should produce quality that is indistinguishable from the original, but practice, judging by the tests of the SoundGuys laboratory on different Android devices, is not confirmed. Most likely, the fault is on low-quality hardware audio encoders embedded in various phone chipsets. It makes sense to use AAC only on Apple devices; with Android you'd better stick with aptX/HD and LDAC." And some article conclusion : "People who do not hear the difference between codecs while testing via a web service claim they hear it when listening to music with Bluetooth headphones. Unfortunately, that is not a joke or a placebo effect: the difference is really audible, but it is not caused by difference in codecs." "The marketing of alternative codecs is very strong: aptX and LDAC are presented as a long-awaited replacement of the “outdated and bad” SBC, which is far from as bad as it is commonly thought of." .. "As it turned out, the artificial limitations of Bluetooth stacks on SBC can be bypassed, so that the SBC will be on par with aptX HD."