This refers to the surround sound configuration (five main speakers and one subwoofer). The film relies heavily on atmospheric tension and a subtle score, which benefit from a multi-channel setup. Film Summary & Context
Based on the novel by Olen Steinhauer, the movie is a "chamber piece" masquerading as a global thriller. It follows two CIA agents and former lovers who meet for dinner to investigate a past terrorist hijacking, only to realize one of them might be a double agent. Analysis Points for a Paper Watch ALL THE OLD KNIVES (2022) WEB-DL 1080p 5 1 1
This indicates the file was losslessly ripped from a streaming service (like Amazon Prime Video). Unlike a "WebRip," which is re-encoded, a WEB-DL is the exact stream data, offering the highest possible digital quality short of a physical Blu-ray. This refers to the surround sound configuration (five