Hierarchical Modulation for Fast Digital TV Channel Change
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Solution Overview
Problem
Existing digital video broadcast systems face long channel change times, often exceeding 10 seconds, due to the inefficiency of existing fast channel change solutions that waste resources and require non-backward compatible system changes.
Innovation Solution
The implementation of hierarchical modulation within digital video broadcast systems, where high priority and low priority signals are used to enable rapid channel changes by compressing audiovisual streams into different Group of Pictures (GOP) structures, allowing receivers to quickly transition between channels without wasting resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If additional bits are used to provide low resolution video for fast channel change, then channel change time is reduced, but system complexity increases and backward compatibility is lost
Solution Approach 1:
The video stream is segmented into two distinct GOP structures: a first GOP structure with more frames for normal video playback, and a second GOP structure with fewer frames for fast channel change. This segmentation allows the receiver to quickly switch channels using the condensed second GOP structure while maintaining the original video quality stream for normal viewing, thus reducing channel change time without compromising overall system complexity or compatibility.
2Loss of time
If additional bits are used to provide low resolution video for fast channel change, then channel change time is reduced, but resource waste increases
Solution Approach 1:
The second GOP structure with fewer frames is prepared in advance as a preliminary compressed version of the video stream. This pre-compressed structure allows the receiver to rapidly decode and display a usable video image during channel transitions without wasting additional transmission bits, as the compression is achieved through temporal subsampling rather than additional data.
3Loss of time
If existing systems are changed to provide fast channel change, then channel change time is reduced, but backward compatibility is lost requiring new receivers
Solution Approach 1:
The transmitted stream universally contains both the first GOP structure (normal video) and the second GOP structure (fast channel change video) simultaneously. This multi-functional approach allows existing receivers to continue using the normal video stream for standard playback, while new receivers with enhanced capabilities can exploit the second GOP structure for fast channel changes, thus maintaining backward compatibility while enabling advanced functionality.
4Manufacturing precision
If more frames are used in GOP structure, then video quality is improved, but channel change time increases
Solution Approach 1:
The system dynamically adapts the GOP structure based on the operational mode: during normal video playback, the receiver uses the first GOP structure with more frames for high video quality; during channel transitions, the receiver switches to the second GOP structure with fewer frames for rapid decoding and display. This dynamic switching resolves the contradiction between video quality and channel change time by optimizing the frame structure for the current operational context.
Data Source
AI summary
Providing a fast channel change function in a digital television system by hierarchically modulating each channel to provide both high priority (long interleave) and low priority (short interleave) signals, wherein a receiver may rapidly demodulate and use information within the low priority signal of a new channel to more rapidly change to the new channel.