DVR Trick Play via Decode Cost Graph
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Solution Overview
Problem
Conventional digital video recorders (DVRs) provide a crude and resource-intensive trick play experience due to their handling of trick play functions under older MPEG-2 standards, resulting in imprecise repositioning and low frame rates, despite advancements in codecs like VC1 and AVC.
Innovation Solution
A method for constructing a dependency graph in a DVR to select and decode pictures based on their decode costs, allowing efficient resource usage and improved playback speed while maintaining high video quality, by determining the minimum set of pictures needed for decoding and displaying, particularly under the MPEG-4 standard which allows for more frames in the cache.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional trick play methods are used in DVRs, then basic playback functionality is provided, but the trick play experience is crude and resource-intensive with imprecise repositioning and low frame rates
Solution Approach 1:
The system pre-calculates and stores decode costs for all pictures in the video stream during encoding or initial processing. This preliminary action allows the trick play function to quickly select optimal pictures without real-time computation, improving performance while reducing runtime resource consumption.
Solution Approach 2:
The invention replaces the conventional mechanical approach of sequential picture decoding with a computational graph-based system. By constructing a dependency graph and using cost-based selection algorithms, the system substitutes brute-force decoding mechanics with intelligent computational selection, achieving better performance with lower resource usage.
2Reliability
If all pictures are decoded to ensure complete video representation, then video quality is maintained, but processing time and computational resources increase significantly
Solution Approach 1:
The system extracts only the essential pictures needed for trick play functionality by analyzing the dependency graph and selecting pictures with minimum decode costs. Non-essential pictures are excluded from decoding, maintaining acceptable video quality while significantly reducing processing time and resource consumption.
Solution Approach 2:
The invention changes the parameter selection criteria from decoding all pictures to selecting pictures based on cost metrics. By introducing cost parameters that evaluate decode complexity and temporal proximity, the system optimizes the balance between video quality and processing efficiency through parameter-based selection rather than universal decoding.
3Adaptability or versatility
If the frame cache size is increased to store more reference pictures, then decoding flexibility improves, but memory resource consumption increases
Solution Approach 1:
The system dynamically determines the optimal frame cache size based on the specific trick play requirements and video stream characteristics. Rather than using a fixed large cache, the system adapts the cache size to the minimum necessary amount, providing sufficient decoding flexibility while conserving memory resources through dynamic adjustment.
Solution Approach 2:
The invention applies partial action by storing only the necessary subset of reference pictures in the frame cache rather than all possible reference pictures. The dependency graph analysis identifies which pictures are actually needed for trick play operations, allowing the system to cache only those pictures, thus providing adequate flexibility with reduced memory consumption.
Data Source
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AI summary
Techniques for selecting a picture of a video program for display in accordance with a selected trick play mode of a DVR are described herein. Sometimes, when desired playback speed is faster than normal, a DVR is forced to select some pictures to play and some pictures to skip. Ideally, in order to preserve "smooth" viewing quality, the next picture to be displayed should be temporally close to the currently displayed picture. Since some pictures can take longer to decode than others, accounting for picture decoding costs helps ensure that the best picture can be selected for decoding given playback speed requirements. According to one embodiment of the invention, for each picture of a plurality of pictures in a video data stream, a DVR determines a decoding cost for that picture. Based on the determined costs, the DVR selects a particular picture. The DVR outputs the selected picture for display.