Dual Decoder Reverse Playback Buffering
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Solution Overview
Problem
Moving image playback apparatuses require significant time to acquire and display reversely-played back images after switching from forward playback, due to the need to sequentially decode image data in a specific GOP structure, leading to delays in reverse playback initiation.
Innovation Solution
The apparatus employs two decoders and a controller to pre-read and decode image data from two successive GOPs, allowing for simultaneous decoding and buffering of image data, enabling immediate output when switching to reverse playback and reducing startup time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If sequential decoding from I-picture in the immediately preceding GOP is performed to decode B-picture, then decoding accuracy is improved, but reverse playback startup time increases
Solution Approach 1:
The patent applies preliminary action by pre-decoding and storing image data of a predetermined number of frames in the output buffer before reverse playback is requested. This allows the system to have decoded frames ready in advance, eliminating the need to sequentially decode from I-picture when reverse playback starts, thus reducing startup time while maintaining decoding accuracy through proper buffer management
Solution Approach 2:
The patent segments the decoding process by separating the pre-decoding phase (where a predetermined number of frames are decoded and stored in buffer) from the reverse playback phase. This segmentation allows the system to prepare decoded frames in advance without affecting the GOP structure integrity, enabling faster reverse playback startup while maintaining the necessary decoding accuracy
2Loss of time
If multiple decoders are used to pre-decode and buffer image data, then reverse playback startup time is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the output buffer to serve multiple functions: it acts as both a display buffer during normal playback and a pre-decoded frame storage during reverse playback preparation. This multi-functionality eliminates the need for separate decoder configurations, reducing device complexity while still achieving fast reverse playback startup through efficient buffer management
Data Source
AI summary
A moving image playback apparatus includes two decoders and one output buffer. In standby, using I-picture in a specified GOP as a reference, a controller causes a storage device to sequentially read first coded image data of the pictures in a first GOP preceding a specified GOP and the pictures up to I-picture in the specified GOP, and causes a first decoder to decode the first coded image data, during which the controller causes the storage device to sequentially read second coded image data of the pictures in the specified GOP and the pictures up to I-picture in a second GOP following the specified GOP, and causes a second decoder to decode the second coded image data. Thereafter, outputs from the first and second decoders are written to the output buffer, and outputted from the output buffer immediately upon start of reverse playback, and moving images are played back.