4K Movies - What is Blu-ray Remux?

REMUX is the process of extracting video and audio streams from a Blu-ray disc and placing them into a new container (usually MKV) without transcoding and without any loss of quality. The bitrate, codec, and every bit of data remain unchanged—a 1:1 copy of the original disc.

Remux ≠ encode. If the file name does not include the word REMUX, it is an encode that is, a transcoded file with some loss of quality. Key characteristics of a remux:

Video codec: the original from the disc HEVC/H.265 (for UHD), AVC/H.264, or VC-1 (for 1080p BD).
Bitrate: 40 to ~144 Mbps for 4K UHD, compared to 15-20 Mbps for streaming.
HDR: HDR10, HDR10+, and Dolby Vision are fully preserved (with the caveat below).
Audio: Lossless TrueHD Atmos, DTS-HD MA, FLAC all in their original formats!

The only exception: Dolby Vision FEL: Most Blu-ray players decode Dolby Vision Full Enhancement Layer (FEL), but most media players do not support a second video decoder for FEL when remux. Therefore, in remux, DV is more often encoded in Profile 7 (base layer: HDR10 + enhancement layer), and playback depends on the player.