Digital Receiver Stream Switching for Clear and CA Channels
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Solution Overview
Problem
Current digital receivers experience errors and noise in clear channels due to unnecessary descrambling processes, and malfunction when attempting to switch CA-scrambled streams for copy protection, leading to an endless loop.
Innovation Solution
A digital receiver with detection means to determine if a stream is CA-scrambled, and output either decrypted or undecrypted signals based on this information, using a configuration with separate receiving, decryption, and output means to prevent noise and ensure proper switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If descramble processing is performed on all channels including clear channels, then decryption capability is maintained, but errors occur in clear channel streams and noise appears in video and audio signals
Solution Approach 1:
The patent applies preliminary action by detecting whether a channel is CA-scrambled or clear before the digital stream is input to the decryption module. The control circuit determines the channel type in advance and pre-configures the switching state of the stream switching circuit accordingly. This prevents unnecessary descrambling of clear channels and avoids the harmful effect of errors and noise in video and audio signals.
Solution Approach 2:
The patent introduces a control circuit as an intermediary between the channel selection and decryption module. This control circuit receives information about whether the selected channel is CA-scrambled or clear, determines the appropriate switching state, and controls the stream switching circuit accordingly. This intermediary layer enables intelligent routing without requiring complexity in the decryption module itself.
2Adaptability or versatility
If decryption module is always active, then CA-scrambled channels can be received, but power consumption increases and clear channel reception becomes problematic
Solution Approach 1:
The patent implements dynamic operation of the decryption module by controlling it to operate only when a CA-scrambled channel is selected. The control circuit detects the channel type and activates the decryption module only when necessary. When a clear channel is selected, the decryption module remains inactive, reducing power consumption while maintaining the capability to receive CA-scrambled channels when needed.
3Reliability
If stream switching is implemented without accurate detection, then clear and scrambled channels can be routed differently, but errors and endless loops occur due to ineffective switching
Solution Approach 1:
The patent employs feedback by using detection means to accurately determine whether the selected channel is CA-scrambled or clear, and using this information to control the stream switching circuit. The control circuit receives feedback about the channel type and adjusts the switching state accordingly. This feedback mechanism ensures accurate routing without causing errors or endless loops that would occur with ineffective switching control.
Data Source
AI summary
When a channel which is not scrambled is selected, an error occurs in a digital stream processed in a CA processing module, which causes noises to occur in video and audio signals to be viewed. If a FAT channel to be received is a channel that is not CA-scrambled, a digital stream is directly supplied from a FAT demodulator to a demultiplexer without passing the digital stream through an external processing module. As a result, no noise occurs in video and audio signals to be viewed because the video and audio signals are not influenced by an error of the digital stream that occurs in the processing module.