USB Controller Logical Pipes for CI Host Video Jitter
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Solution Overview
Problem
Current CI and CI Plus systems face challenges in optimizing video jitter and latency for optimal channel change performance, particularly due to the limitations of the PCMCIA interface and the variability in video bandwidth, which affects decoder buffer requirements and channel change times.
Innovation Solution
The implementation of a USB controller using logical pipes for transferring CA encrypted and decrypted signals, employing isochronous pipes for DVB-originating traffic to minimize jitter and bulk pipes for IP-originating traffic to handle variable bitrate requirements, while avoiding TS-packet-level encapsulation and utilizing error detection and correction efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If USB bulk pipes are used for IP-originating traffic, then variable bitrate requirements are handled, but video jitter increases compared to isochronous pipes
Solution Approach 1:
The patent applies different USB transfer modes to different traffic types: isochronous pipes for DVB traffic requiring low jitter, and bulk pipes for IP traffic requiring variable bitrate handling. This local differentiation optimizes performance for each traffic type without compromising the other.
Solution Approach 2:
The system dynamically selects the appropriate USB pipe type based on the traffic source (DVB or IP) and characteristics, allowing flexible adaptation to different bandwidth requirements while maintaining optimal jitter performance for each type.
2Reliability
If larger decoder buffer is used, then buffer underruns are avoided, but channel change time increases
Solution Approach 1:
The system performs preliminary buffering of video data before transmission to the CICAM device. By pre-buffering data in the USB host controller and using isochronous pipes with guaranteed bandwidth, the system avoids buffer underruns during channel changes without requiring large decoder buffers, thus reducing channel change time.
Solution Approach 2:
The patent replaces the traditional mechanical approach of using large physical buffers with a software-based USB isochronous transfer mechanism that guarantees bandwidth allocation. This substitution allows smaller buffers to achieve the same reliability in preventing underruns.
3Adaptability or versatility
If PCMCIA interface is used, then backward compatibility is maintained, but communication speed is limited and physical space is increased
Solution Approach 1:
The patent replaces the outdated PCMCIA mechanical interface with a modern USB interface. This substitution provides faster communication speeds, reduced physical space requirements, and lower implementation costs while maintaining full functional compatibility through software-based CI/CI+ protocol implementation over USB.
Data Source
AI summary
The invention provides a Common Interface, Cl, host (10) comprising a Universal Serial Bus, USB, controller (30) for connecting to a USB device (31) of a Common Interface Conditional Access Module, CICAM, (20) the USB controller being configured to use - a first logical pipe (33) for transferring control information between the CICAM and the Cl host; and - a second logical pipe (35) for transmitting to the CICAM a first CA encrypted signal. - a third logical pipe (37) for receiving a first CA decrypted signal, corresponding to the first CA encrypted signal, from the CICAM, wherein USB isochronous pipes are used as the second logical pipe (35) and the third logical pipe (37) when the first CA encrypted signal originates from a DVB broadcast and USB bulk pipes are used as the second logical pipe (35) and the third logical pipe (37) when the first CA encrypted signal originates from an Internet source.