Audio Video Transport Synchronization Without Decoding Time Stamps
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Solution Overview
Problem
Conventional MPEG-2 systems require decoding time stamps (DTS) for audio and video synchronization, which increases computational complexity and storage costs, and the use of time stamps longer than 32 bits further complicates decoding.
Innovation Solution
A method and system for audio and video transport that synchronizes streams using 24-bit presentation time stamps (PTS) and 32-bit system clock samples (SCS) without DTS, allowing for PTS extrapolation when frames lack associated PTS fields, reducing decoder complexity and computational requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If decoding time stamps (DTS) are used for audio and video synchronization, then synchronization accuracy is improved, but computational complexity and storage costs increase
Solution Approach 1:
The patent extracts and removes the DTS field from the packetized elementary stream, keeping only the PTS field. This eliminates the need for DTS-related decoding operations while maintaining synchronization through PTS alone, thereby reducing computational complexity without sacrificing synchronization accuracy
Solution Approach 2:
The patent discards the DTS information that would otherwise be stored and processed, relying instead on the PTS field and system clock samples. This reduces storage requirements and computational burden while the synchronization function is recovered through the simplified PTS-based mechanism
2Measurement precision
If time stamps longer than 32 bits are used, then synchronization precision is improved, but computational complexity increases due to multiple fetches
Solution Approach 1:
The patent changes the parameter of time stamp length from potentially longer than 32 bits to exactly 32 bits (using 24-bit PTS with system clock samples). This standardization eliminates the need for multiple memory fetches to access time stamp values, thereby improving decoding speed while maintaining sufficient precision through the combination of PTS and system clock sampling
3Reliability
If DTS fields are included in the data stream, then synchronization capability is improved, but data stream size and processing overhead increase
Solution Approach 1:
The patent extracts only the necessary synchronization information (PTS field and system clock samples) from the traditional DTS-based system. By removing the redundant DTS field entirely, the data stream size is reduced while synchronization capability is maintained through the streamlined PTS mechanism
Solution Approach 2:
The patent uses lightweight 24-bit PTS fields instead of more substantial DTS structures. These shorter, simpler time stamp representations reduce the quantity of data that must be transmitted and processed, while still providing the necessary synchronization functionality
Data Source
AI summary
Aspects of a method and system for processing audio and video transport may comprise synchronizing streams with associated program content based on 24-bit presentation time stamps (PTSs) and 32-bit system clock samples (SCSs) field without using decoding time stamps (DTSs). A PTS field may be provided as part of a packetized elementary stream (PES) packet syntax. An SCS field may be provided as part of a transport stream (TS) syntax. A system clock (STC) may be determined from received SCS values. Video and/or audio data may be decoded as soon as they arrive and when there is at least one display and/or presentation frame buffer available. The video and/or audio data may be presented for display and/or play based on a comparison of the PTS and STC values. When a frame does not have an associated PTS, a PTS extrapolation operation may generate an extrapolated PTS value from previously received PTSs.