The and Fair Use in video essays. Encoding Video for Blu-Ray using H264/AVC - Page 19
: This is likely a "release tag" or "signature" from the group or individual who encoded and uploaded the file. Film Context: Black Adam (2022) bl-ck-ad-m-2022-720p-h-nd-x264-1xb3t-2-mkv
The string can be decoded to understand the technical specifications of the video file: The and Fair Use in video essays