A PSSH (Protection System Specific Header) box is a small block of DRM-specific data carried inside an encrypted media file (and signaled in the manifest). Each DRM system has its own PSSH containing what that system needs - key identifiers and the information to construct a license request.
PSSH is what makes Common Encryption multi-DRM work in practice: one encrypted file can carry a Widevine PSSH and a PlayReady PSSH side by side, so whichever DRM the device uses finds its own instructions and fetches the right license. Correct PSSH generation at packaging time is a frequent source of multi-DRM playback bugs when it is wrong or missing for a given system.
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
A missing or wrong PSSH box is a common reason one DRM plays on a device while another fails with a license error. Our seven-volume handbook covers the whole video stack; for PSSH start with Volume 3 on DRM, players and ABR, with Volume 2 on HLS, MPEG-DASH and CMAF packaging and Volume 1 on encoding. Written by Nikolay Sapunov, CEO at Fora Soft.
Widevine works but FairPlay or PlayReady fails, and you suspect the PSSH box?
Send us a manifest and a sample segment, and we will check your PSSH and encryption signalling and return a fix list for your packager. 250+ video products shipped since 2005.
