MQA is a proprietary format for storing audio that “alleges” to be higher quality than open source lossless, such as FLAC, or ALAC (Apple Lossless Audio Codec).

MQA stands for Master Quality Authoritative. It is a scam. Very scientific audio tests have revealed the audio is actually degraded by the process - a process they will not explain.

They just do a lot of hand waving and talk about “experience.”

The reality is, without trained ears that have sustained almost no damage, the difference between AAC 256kbps and a high res FLAC/ALAC is not perceptible. People like #[3]​ and I (I worked in a studio for a while) can hear it, on expensive equipment.