Vega 0.22 Widevine CDM rejects encryptionScheme: 'cbcs'

Vega Open Beta Bug Reports
1

Platform: Vega 0.22, @amazon-devices/react-native-w3cmedia 2.1.99, Shaka 4.16.13 (per the official integration guide).

When Shaka calls requestMediaKeySystemAccess (or mediaCapabilities.decodingInfo) for com.widevine.alpha with an encryptionScheme: 'cbcs' capability, Vega’s CDM logs:

WARN  EncryptedMediaImpl: requestMediaKeySystemAccess. Unsupported encryptionScheme passed: cbcs. skipping

…and drops the capability. HLS streams with CBCS-encrypted audio or video (any stream where the init segment’s tenc box has scheme_type=cbcs) then get decrypted as CENC and produce decoder garbage. Symptom: video freezes on the first frame with no audio and no JS-visible error.

Questions:

  1. Is CBCS support planned, and if so when?

  2. Is the CBCS decryption code path entirely absent, or is it just not exposed through EME negotiation? (i.e. would supplying CBCS segments without the EME hint still decrypt?)

  3. Is there an alternate keysystem string or flag that selects the CBCS path today?

Thanks!

3

Hi @ScottW ,

Welcome to the Amazon Developer Community.

We are checking internally on the CBCS support and will let you know as soon as we have answers.

Thanks,
Rohit

5

Hi @ScottW ,

Thank you for your patience while we investigated this.

To answer your questions:

  1. CBCS is already supported on Vega. No additional work is needed on that front.

  2. The CBCS decryption path is fully present and works. The issue is only in the EME negotiation layer, not in actual decryption.

  3. No alternate keysystem string is needed. com.widevine.alpha works for both CENC and CBCS.

Workaround: Remove the drm.advanced[keySystem].encryptionScheme configuration from your Shaka setup. Without that hint, the CDM will handle CBCS streams correctly.

Let us know if the workaround resolves the issue for you.

Thanks,
Aishwarya

6

Hi @ScottW,

Just checking in — were you able to try the workaround (removing drm.advanced[keySystem].encryptionScheme from your Shaka config)? Let us know if that resolved the CBCS playback issue on your end.

Thanks,
Aishwarya