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Clearkey

Overview

We discuss here how to use ClearKey encryption in GPAC.

We assume that you are familiar with encrypting ISOBMFF files with MP4Box. If not, please read the Encryption wiki first.

ClearKey is a simple key distribution system for MPEG-DASH using plain text key exchange over https. For more info, check https://github.com/Dash-Industry-Forum/ClearKey-Content-Protection

Fetching of keys through ClearKey is supported in GPAC decryptor and does not need to be configured.

DRM config file

ClearKey can be used with any scheme types defined in CENC, and does not need any specific info (e.g. PSSH).

Using MP4Box

You first need to encrypt your source:

MP4Box -crypt drm.xml source.mp4 -out cypted.mp4

You can then dash your source(s). If all streams share the same ClearKey licence server URL, specify ckurl option of dasher:

MP4Box -dash 1000 cypted.mp4 -out dash/manifest.mpd:ckurl=https://ck.gpac.io/GetLicence

If each source has its own licence URL: 

MP4Box -dash 1000 cypted.mp4:#CKUrl=https://ck.gpac.io/GetLicence cypted2.mp4:#CKUrl=https://ck.gpac.io/GetLicence2  -out dash/manifest.mpd

Using gpac for single-pass encrypt and dash

If all streams share the same ClearKey licence server URL, specify ckurl option of dasher:

gpac -i src.mp4 cecrypt:cfile=drm.xml -o dash/manifest.mpd::ckurl=https://ck.gpac.io/GetLicence

Note that we use double colon separator, as the ClearKey URL also uses colons which will break parameter inheritance. One way to avoid this is to use: 

gpac -i src.mp4 cecrypt:cfile=drm.xml  -o dash/manifest.mpd --ckurl=https://ck.gpac.io/GetLicence

If streams have different ClearKey licence server URL (we assume a single DRM.xml is needed here), specify CKUrl pid property on sources:

gpac -i src.mp4:#CKUrl=https://ck.gpac.io/GetLicence  -i src2.mp4:#CKUrl=https://ck.gpac.io/GetLicence2  cecrypt:cfile=drm.xml -o dash/manifest.mpd