MPEG Rewind Decoding Frame Memory Management
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Solution Overview
Problem
Existing decoder systems face challenges in efficiently displaying MPEG video streams in rewind mode due to the high computational resources and storage requirements, as they are adapted for forward decoding, leading to inefficiencies in frame memory usage and potential delays in displaying backward content.
Innovation Solution
A method that optimizes frame memory usage by prioritizing the overwriting of obsolete or low-decoding-cost pictures, suspending decoding when necessary, and using an indexation table to manage the display of pictures in rewind mode, allowing for efficient decoding and display with a minimum number of frame memories, especially when less than the number of pictures in a GOP.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MPEG stream is decoded in rewind mode using conventional methods, then all pictures of a GOP can be displayed, but a large storage capacity is required for frame memories to store decoded pictures
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the display order of pictures in rewind mode before actual playback. The system determines which pictures need to be decoded and in what order, allowing efficient memory management during playback without requiring large frame buffers
Solution Approach 2:
The patent changes the parameter of picture display order by implementing a non-linear display sequence that differs from the encoding order. By using a display order table that maps picture positions differently for rewind mode, the system reduces memory requirements while maintaining display continuity
2Quantity of substance
If the MPEG stream is decoded in rewind mode with limited frame memories, then storage capacity is reduced, but the decoding rate must be sufficiently high to decode each picture
Solution Approach 1:
The system performs preliminary analysis to determine the exact decoding sequence and picture dependencies before playback. This allows the decoder to be pre-configured with the minimal set of pictures that must be decoded, reducing the computational burden during actual rewind playback
Solution Approach 2:
The patent implements skipping by identifying and eliminating pictures that do not need to be decoded for rewind display. By analyzing the GOP structure and picture dependencies, the system skips unnecessary decoding operations, reducing the required decoding rate
3Device complexity
If B pictures are skipped during rewind reading, then decoding complexity is reduced, but picture quality and continuity are compromised
Solution Approach 1:
The patent applies local quality by treating different picture types differently based on their position and dependency in the rewind sequence. Instead of uniformly skipping all B pictures, the system selectively processes pictures based on local requirements for maintaining display continuity
Solution Approach 2:
The system dynamically adjusts the decoding strategy based on the current playback position and the structure of the GOP. The decision to decode or skip pictures is made dynamically rather than following a fixed rule, allowing optimal balance between complexity and continuity
Data Source
AI summary
A process for decoding and for displaying in rewind mode pictures of a stream of picture data compressed according to the MPEG standard using a specified number N of frame memories each adapted for storing a decoded picture, where N is an integer greater than or equal to 4, applies rules for selecting a frame memory when a frame memory is to be overwritten so as to allow the storage of a new picture to be decoded.