Android License Workflow

Online playback — end to end

For online playback the workflow is the MediaDrm session lifecycle wrapped in the wider media stack:

ExoPlayer integration sketch

val mediaDrmCallback = HttpMediaDrmCallback(LICENSE_URL, httpDataSourceFactory)
    .apply {
        setKeyRequestProperty("Authorization", "Bearer $appToken")
    }

val drmSessionManager = DefaultDrmSessionManager.Builder()
    .setUuidAndExoMediaDrmProvider(C.WIDEVINE_UUID, FrameworkMediaDrm.DEFAULT_PROVIDER)
    .setMultiSession(true)            // helps with key rotation in live
    .build(mediaDrmCallback)

val mediaSource = DashMediaSource.Factory(httpDataSourceFactory)
    .setDrmSessionManagerProvider { drmSessionManager }
    .createMediaSource(MediaItem.fromUri(MANIFEST_URL))

player.setMediaSource(mediaSource)
player.prepare()
player.play()

The integrator's surface area is small but the hooks matter:

• setKeyRequestProperty — attach the auth token here.
• setMultiSession(true) — required when key rotation creates multiple KIDs in a single playback.
• setForceSessionsForAudioAndVideoTracks — when audio and video have different KIDs.

Offline playback

The offline flow has two parts: download time and replay time.

At download time

val drm = MediaDrm(C.WIDEVINE_UUID)
val sessionId = drm.openSession()
val req = drm.getKeyRequest(
    sessionId, initData, "video/mp4",
    MediaDrm.KEY_TYPE_OFFLINE, null
)
val resp = httpPost(licenseUrl, req.data)
val keysetId = drm.provideKeyResponse(sessionId, resp)   // returns keysetId
drm.closeSession(sessionId)
saveKeysetIdForContent(contentId, keysetId)

At replay time (offline)

val drm = MediaDrm(C.WIDEVINE_UUID)
val sessionId = drm.openSession()
drm.restoreKeys(sessionId, savedKeysetId)
val crypto = MediaCrypto(C.WIDEVINE_UUID, sessionId)
codec.configure(format, surface, crypto, 0)
// decode normally; no network

Releasing the offline keys

When the user finishes a rental window or deletes the download:

val req = drm.getKeyRequest(
    null /* scope */, savedKeysetId,
    null, MediaDrm.KEY_TYPE_RELEASE, null
)
val resp = httpPost(licenseUrl, req.data)
drm.provideKeyResponse(null, resp)

The release flow is required by some studio policies — it tells the licence server "this device has surrendered its persistent licence." Without it, telemetry on offline usage is incomplete.

Renewal / key rotation in Android

When the CDM emits EVENT_KEY_REQUIRED, ExoPlayer re-runs the key request flow with the existing session. The application typically does nothing special — but the licence server must accept renewal requests on the same session and return fresh keys.

For live with key rotation, setMultiSession(true) lets ExoPlayer hold one session per active KID.