No its a Bluetooth audio thing. Most music files general public listens to are compressed music files and Bluetooth Compress that more. Apt x dies something with those files or something to make it sound better with Bluetooth headphone or headsetsDo you mean the audio compression?
Do you mean the audio compression?
summary of aptx here: Can aptX give you better sound over Bluetooth? - CNET
The aptx.com web site does not (yet at least) list the Note 4: Search | APTX
Since previous Notes had it, though, it seems likely to me that the Note 4 will as well.
Yes!
Just got my Note 4 yesterday and paired it with my Sony MDR-10RBT Bluetooth Headphones moments ago. When I am playing or streaming music, the LED on the headphones quickly flashes 3 times in a row every few seconds indicating High Quality AAC or aptX mode -- just like with my Galaxy S3.