Remultiplexing Timing Artifact Minimization
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Solution Overview
Problem
Timing artifacts occur during the remultiplexing of single program transport streams into a multi-program transport stream in Edge QAMs due to large and uncertain delays in the IP stack and input buffer, leading to buffer overflow violations and video/audio artifacts in digital televisions.
Innovation Solution
Implementing methods to control the remultiplexing process by buffering and rate-controlling single program transport streams, limiting consecutive packet transfers, and using multiple program clock reference values to pace data transfer, ensuring packets are released only after a previous program clock reference value is greater than the system time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the internal remultiplexer restamps TS packets with a new program clock reference (PCR) to handle large and uncertain delays in the IP stack and input buffer, then the system can accommodate dynamically varying delays, but timing artifacts are created that are noticeable on digital televisions
Solution Approach 1:
The system performs preliminary rate control calculations and buffer management before packets are transferred to the multiplex buffer. By pre-calculating transfer rates and controlling packet flow in advance, the system avoids the need for PCR restamping while preventing buffer overflows and timing artifacts.
Solution Approach 2:
The system implements feedback mechanisms by monitoring buffer levels and adjusting packet transfer rates dynamically. This feedback control ensures that packets are released at appropriate rates based on actual buffer conditions, maintaining timing synchronization without creating artifacts.
2Productivity
If multiple single program transport streams are remultiplexed into a multi-program transport stream without rate control, then the remultiplexing process is simple and fast, but buffer overflow violations occur and timing constraints are not met
Solution Approach 1:
The system changes the parameter of packet transfer rate by calculating and applying rate control based on buffer conditions. This dynamic parameter adjustment allows the system to maintain high productivity while ensuring timing constraints are met by transferring packets at optimized rates rather than constant maximum rates.
3Productivity
If packets are transferred from single program transport streams to the multiplex buffer without limiting consecutive packets, then the transfer process is efficient, but timing artifacts and buffer overflow violations increase
Solution Approach 1:
The system applies partial rate control by transferring packets at calculated rates that are sufficient to maintain buffer utilization but not excessive enough to cause overflows. This partial action approach balances efficiency with reliability, preventing timing artifacts while maintaining good throughput.
Data Source
AI summary
A particular implementation for controlling single program transport streams during remultiplexing to a multiple program transport stream uses a series of leaky bucket buffers to minimize timing artifacts in the multi-program transport stream. Another implementation for controlling the remultiplexing process limits the number of consecutive packets to be transferred from each single program transport stream, or controls the multiplex frequency of each single program transport stream within the multi-program transport stream. An alternative implementation controls the remultiplexing process using multiple program clock reference values such that packets from each single program transport stream are released only after a previous program clock reference value is greater than the system time.