Decoder Trick Mode Transition Error Handling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional video servers often fail to properly handle trick mode transitions in video-on-demand streams, leading to errors due to unmarked time base discontinuities and miscalculated time stamps, which result in poor video playback during transitions between regular and trick modes.
Innovation Solution
A decoder is configured to handle unmarked time base discontinuities by comparing system time clocks with packet time stamps, disabling and recalculating time management as needed, and skipping initial B-pictures during transitions to correct miscalculated time stamps, thereby ensuring accurate playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the video server transmits video streams with time base changes during trick mode transitions, then VCR-type capabilities (fast forward, reverse, pause) are enabled, but time base discontinuities cause decoder errors and playback failures
Solution Approach 1:
The decoder proactively compares incoming time stamps with the system time clock before processing video packets. When a time base discontinuity is detected (difference exceeds threshold), the decoder preemptively adjusts the system time clock and disables time management, preventing decoder errors before they occur. This preliminary detection and correction mechanism ensures reliable transitions without requiring server-side modifications.
2Measurement precision
If the decoder strictly follows time stamps from the video server, then synchronization is maintained, but miscalculated time stamps cause playback errors during transitions
Solution Approach 1:
The decoder implements a feedback mechanism where incoming packet time stamps are continuously compared with the system time clock. When the difference exceeds a predetermined threshold, the system detects miscalculated time stamps and corrects the system time clock accordingly. This feedback loop ensures that even when the server provides incorrect time stamps during transitions, the decoder maintains accurate synchronization and reliable playback.
3Speed
If the system changes time base during trick mode transitions, then fast forward and reverse functionality is achieved, but B-pictures with incorrect time stamps cause decoding errors
Solution Approach 1:
The decoder skips B-pictures received during trick mode transitions before processing them. This preliminary filtering action prevents B-pictures with incorrect time stamps from causing decoding errors. By selectively discarding potentially problematic B-pictures during the transition period and only processing them after the time base change is complete, the decoder maintains both fast forward functionality and decoding reliability.
Data Source
AI summary
A system, method, and apparatus for handling transition errors is presented herein. The transition errors include handling unreported time base discontinuities during trick mode transition, miscalculated time stamps during trick mode transition, erroneous sequence end codes, and unreported broken group of picture transmission. Unreported time base discontinuities are detected by comparing the program clock reference (PCR) value of the data packet to the system time clock (STC). If the difference exceeds a predetermined threshold, the STC is set to the PCR value. Miscalculated time stamps are detected by examining the difference in PTS values between temporally adjacent data packets. If the difference is not within a margin of error from predetermined value, the PTS is disabled. Unreported broken groups of pictures are handled by skipping the first two B-frames of the first group of pictures following a trick mode transition. Erroneous sequence end codes are detected by determining whether a packet containing a sequence end code is associated with a time base change. If the packet is not associated with a time base change, the sequence end code is disregarded.