PMT Packet Replacement in Satellite Signal Processing
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Solution Overview
Problem
Existing signal processing methods for satellite broadcasting face challenges in efficiently replacing or deleting the Program Map Table (PMT) without increasing the load on control circuits, requiring large storage capacity and special circuits, which makes them costly and inefficient.
Innovation Solution
A signal processing apparatus and method that incorporates a PID detecting circuit to identify and replace or delete the PMT within a data stream without using a recording medium, eliminating the need for a CPU and simplifying the circuit arrangement by processing control information packets in real-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the PMT is rewritten by searching data on the disc using a control circuit, then the copy control signal can be changed from 'copy once' to 'copy guard', but the load on the control circuit increases and the performance of the receiver is lowered
Solution Approach 1:
The invention separates the PMT rewriting function from the main control circuit by introducing a dedicated rewriting circuit. This circuit is triggered by a specific flag signal and operates independently to replace only the necessary PMT portions, thereby maintaining copy protection while preventing excessive load on the main control circuit and preserving receiver performance.
Solution Approach 2:
The invention introduces a flag signal as an intermediary mechanism. When the PMT needs rewriting, a specific flag is set in the received data stream, which the rewriting circuit detects and acts upon. This intermediary approach allows the control circuit to initiate the rewriting process without directly handling the complex search and replacement operations, thus reducing its load.
2Reliability
If all data are written on a recording medium and the control circuit searches for the PMT, then the PMT can be detected and overwritten, but a large-storage capacity disc becomes necessary and the cost increases
Solution Approach 1:
The invention performs preliminary action by setting a specific flag signal in the received data stream before the PMT rewriting is needed. This flag acts as a pre-marked location indicator, allowing the rewriting circuit to directly locate and rewrite the PMT without searching through stored data on the disc, thereby eliminating the need for large storage capacity.
Solution Approach 2:
The invention extracts the PMT rewriting operation from the main data processing flow and handles it separately through a dedicated rewriting circuit triggered by the flag signal. This extraction allows the system to rewrite only the necessary control information without needing to store or search through the entire data set, reducing storage requirements.
3Reliability
If the PMT is deleted in advance and a new PMT is inserted based on a position signal, then the PMT can be replaced, but a circuit for deleting the PMT and generating position signals is required in addition to the rewriting circuit
Solution Approach 1:
The invention merges the PMT deletion, position signaling, and rewriting functions into a single integrated rewriting circuit. The circuit detects the flag signal, automatically identifies the PMT location, performs deletion, and inserts the new PMT in one unified operation, eliminating the need for separate deletion circuits and position signal generation circuits.
Solution Approach 2:
The rewriting circuit is designed with multi-functionality to handle multiple tasks: detecting the flag signal, locating the PMT, deleting the old PMT, and inserting the new PMT. This universal circuit performs all necessary operations for PMT replacement without requiring additional specialized circuits, thereby simplifying the overall device complexity.
Data Source
AI summary
A data stream inputted to the inventive system from the outside is supplied to a PID (packet ID) extracting circuit 1, in which a PID is detected from a transport stream TS regardless of whether the transport stream TS is a full transport stream TS or a partial transport stream TS. The PID extracting circuit 1 transmits the thus extracted PID and data stream to a TS replacing/deleting circuit 2. The TS replacing/deleting circuit 2 has n 188-byte buffers and is able to set replaced TS packets to the buffers. A control circuit 3 such as a CPU (central processing unit) designates m PIDs relative to the respective buffers and designates the respective PIDs as the PID of the packet to be deleted or the PID of the packet to be replaced. Then, the TS replacing/deleting circuit 2 compares the PID received from the PID extracting circuit 1 with the PID designated by the control circuit 3. If they are identical to each other, then the PID that is set to be replaced is replaced and the PID that is set to be deleted is deleted. Thus, the packet indicative of attribute of data can be replaced satisfactorily.