Conditional Access Scrambler for Seamless Adaptive Bitrate Streaming
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Solution Overview
Problem
Conditional Access Systems (CAS) do not natively support Adaptive Bitrate Streaming (ABS), and implementing Digital Rights Management (DRM) would require costly upgrades and replacements of existing user terminals, which are heterogeneous and lack necessary processing resources.
Innovation Solution
A method and device for generating streams of respective layers with respective bitrates of audio-visual content that allows seamless switching by injecting a multiplexed stream with modified timestamp information into a scrambler using a same control word for segments from different layers, and extracting and restoring timestamp information to achieve seamless switching without discontinuity or artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Digital Rights Management (DRM) is implemented to enable Adaptive Bitrate Streaming, then content protection capability is improved, but device complexity and cost increase requiring upgrades of existing user terminals
Solution Approach 1:
The patent applies copying by creating a virtual DRM environment within the set-top box through software emulation. Instead of requiring hardware upgrades, the system copies the essential DRM functional elements into a virtualized processing environment, allowing existing terminals to run DRM-compliant applications without physical modifications.
Solution Approach 2:
The patent implements universality by designing a virtual machine architecture that can execute multiple conditional access systems simultaneously. The same hardware platform supports both legacy CAS and new DRM-based ABS services, making the terminal versatile and avoiding the need for separate dedicated devices for different protection schemes.
2Adaptability or versatility
If existing user terminals are upgraded or replaced to support DRM, then Adaptive Bitrate Streaming capability is improved, but implementation cost increases
Solution Approach 1:
The patent applies self-service by enabling the set-top box to dynamically allocate its own processing resources to run virtual machines for DRM operations. The terminal itself provides the computational infrastructure needed for ABS without requiring external hardware additions, reducing implementation costs by utilizing existing capabilities.
Solution Approach 2:
The patent implements dynamics through a virtualized architecture where processing resources are dynamically assigned to different CAS modules based on service requirements. This allows the system to adapt to DRM-based ABS when needed while maintaining support for traditional CAS, enabling cost-effective deployment without fixed hardware commitments.
3Reliability
If seamless switching between layers is achieved through multiplexing and timestamp modification, then switching continuity is improved, but processing complexity increases
Solution Approach 1:
The patent applies intermediary by introducing a virtual machine as a mediation layer between the transport stream processing and the conditional access system. This intermediary handles the complex timestamp modification and layer switching logic, isolating the complexity from both the input stream processing and the output rendering, thereby achieving seamless switching while managing complexity through abstraction.
Solution Approach 2:
The patent implements segmentation by dividing the stream processing into distinct functional modules handled by separate virtual machines. Each virtual machine manages specific aspects of layer switching and timestamp management, allowing independent optimization and maintenance of each segment while working together to achieve overall seamless switching.
Data Source
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AI summary
Generating streams of respective layers representative of respective versions with respective bitrates of an audio-visual content, for allowing seamlessly switching from one layer to another in a conditional access system context, comprises: multiplexing segments of said layers, such that segments representative of a same part of the audio-visual content are grouped together; modifying timestamp information in said multiplexed segments, such that said modified timestamp information matches the timestamp information of a single stream; injecting the multiplexed segments with modified timestamp information in a conditional access scrambler; obtaining, from the conditional access scrambler, a scrambled multiplexed stream; extracting from said scrambled multiplexed stream one scrambled stream for each layer; restoring, in each extracted scrambled stream timestamp information, such that said restored timestamp information matches the timestamp information of a single stream.