Video Decoder Non-Linear Access via Intra Refresh Period
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Solution Overview
Problem
Existing video decoding methods struggle with non-linear decoding of video streams encoded using Intra macroblock refresh processes, as they lack frames where all macroblocks are simultaneously refreshed, hindering trick play functionality and error resilience.
Innovation Solution
A video decoder system determines an Intra-refresh period and a second frame offset within the video stream to allow non-linear decoding to start at any arbitrary frame, suppressing display until the user-requested frame is reached, thereby enabling trick play without aggressive Intra frame insertion and improving error resilience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If Intra frames are inserted frequently to support non-linear decoding, then trick play functionality is improved, but error resilience deteriorates due to propagation of prediction errors
Solution Approach 1:
The patent segments the video stream into GOPs with Intra frames at regular intervals, creating discrete recovery points. This segmentation allows non-linear decoding to restart at any Intra frame without propagating errors through the entire stream, thus improving error resilience while maintaining trick play functionality.
Solution Approach 2:
The patent introduces Intra frames as intermediary elements that act as synchronization points and error barriers. These Intra frames serve as mediators between Predictive frames, allowing the decoder to reset prediction state and prevent error propagation, thereby improving reliability without sacrificing random access capability.
2Measurement precision
If Intra frame insertion rate is increased to improve trick play granularity, then non-linear decoding precision is improved, but compression efficiency deteriorates
Solution Approach 1:
The patent changes the temporal parameters of Intra frame insertion by adjusting GOP length to match the desired trick play granularity. By optimizing this parameter, the system achieves sufficient random access precision while minimizing the frequency of computationally intensive Intra encodes, thereby maintaining compression efficiency.
Solution Approach 2:
The patent applies partial Intra encoding only to the first frame of each GOP rather than encoding all frames as Intra. This partial action approach provides sufficient trick play functionality at GOP boundaries while avoiding the compression efficiency penalty of excessive Intra frame insertion throughout the entire stream.
3Reliability
If Intra frames are used to limit error propagation, then error resilience is improved, but rate control deteriorates due to instantaneous bit rate spikes
Solution Approach 1:
The patent implements periodic Intra frame insertion at regular GOP intervals rather than continuous Intra encoding. This periodic action provides error resilience through regular recovery points while smoothing the bit rate profile over time, avoiding instantaneous spikes that would occur with frequent or random Intra frame insertion.
Solution Approach 2:
The patent maintains continuous prediction-based encoding across most frames, reserving Intra encoding only for the first frame of each GOP. This continuity approach ensures steady bit rate output while still providing error propagation limits through periodic Intra frames, balancing rate control with error resilience.
Data Source
AI summary
A video decoder system receives a user request for non-linear decoding of at least one video frame from a video stream encoded using an Intra macroblock refresh process. The request includes a first frame offset corresponding to a user requested first decoding frame within the video stream for commencing the non-linear decoding. The decoder system: determines an Intra-refresh period corresponding to at least one encoded Predictive frame in the video stream during which all macroblocks in the user requested first decoding frame are Intra encoded at least once; determines a second frame offset as a function of the Intra-refresh period and the user requested first frame offset, the second frame offset corresponding to a second decoding frame within the video stream. Finally, the decoder system decodes the video stream starting at the second decoding frame and suppresses the display of the video stream until the first decoding frame.