Refers to the High Definition resolution (1920x1080 pixels).
The filename provides specific details about the video quality and encoding: Chernobyl S01 BluRay 1080p X264-HDHub4u.zip
This is a free software library for encoding video streams into the H.264/MPEG-4 AVC format, which balances file size with high image quality. Refers to the High Definition resolution (1920x1080 pixels)
