Question/Issue
In DRM content packaging, when is multi-key packaging used? And how can multi-key packaging be applied?
Short Description
Multi-key packaging refers to encrypting different tracks with different encryption keys when packaging ABR (Adaptive Bitrate) streaming content. Typically, video tracks are classified by resolution such as SD (576p or lower), HD (720p or higher), and UHD (4K or higher), and video and audio tracks are encrypted with separate keys. In some cases, audio tracks may not be encrypted.
Compared to single-key packaging, which encrypts all tracks with a single key, multi-key packaging provides the following advantages:
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License key control based on the security level of client devices
- For devices that support only software-level security or do not support HDCP, only the license key for SD quality can be provided, preventing leakage of HD or higher quality content.
- Such security requirements are increasingly applied to premium content, including Hollywood movies.
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Playback quality control based on the content service business model
- For services that differentiate between premium and standard users, playback quality can be restricted by user tier using multi-key content.
- If a service provides only SD quality to standard users, multi-key content can be delivered using multi-manifest URLs (mpd or m3u8 files containing only SD tracks).
Resolution
Multi-key packaging can be applied in the following ways depending on the packaging method.
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DoveRunner CLI Packager
- When using the CLI packager, specify the--multi_keyparameter together with source video files for multiple resolutions.
- SD/HD/UHD keys are automatically applied based on each track’s video resolution. If you want to divide tracks using a custom resolution threshold, additional options such as--max_sd_heightcan be configured.
- If the--generate_tracktype_manifestsparameter is specified, track-type-specific manifest files are generated.
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Third-party packaging via CPIX/SPEKE APIs
- When using third-party transcoders or packagers such as AWS Elemental Media Services or Bitmovin Encoder, multi-key packaging must be supported by the corresponding service. You can refer to the relevant guides in the Content Packaging Guide.
- Even if a dedicated guide is not provided, if the service supports the CPIX specification in accordance with DASH-IF standards, multi-key integration can be implemented by referring to the CPIX API Integration Guide.
To control track-level DRM security policies for multi-key packaged content, the corresponding policy settings must be applied in the license token or custom data used during client integration. For detailed instructions, refer to the DRM Multi-key Implementation Guide.