Common Encryption (CENC) Quick Reference — cenc vs cbcs

A one-page reference to choose an encryption scheme before you lock a packaging config or sign a DRM contract: the two schemes that ship (cenc = AES counter mode read by Widevine and PlayReady; cbcs = AES chaining mode with a 1:9 pattern read by all three including FairPlay), the cbcs-everywhere rule and the cenc-only black-screen warning, the four signaling boxes (schm, tenc, senc, pssh) and what default_KID means, the packaging decision (cbcs default; cenc only as a deliberate legacy fallback