Rapid Channel Change via B-Frame Discarding in Switched Digital Video
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Solution Overview
Problem
Conventional methods for rapid channel changes in switched digital video networks require additional bandwidth, leading to reduced DSL serving area, fewer video streams, or compromised services, as they necessitate temporarily increasing transmission rates to transfer video delay from network devices to decoders.
Innovation Solution
Intelligently discarding video frames in the network device queue, specifically moving B-Frames forward in time, allowing decoders to conceal missing frames by repeating previous ones or predicting them, thus reducing the need for increased bandwidth during channel changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the network device transmits video at a faster than normal rate to transfer delay to the decoder, then rapid channel change is achieved, but additional DSL capacity is required which reduces serving area and stream numbers
Solution Approach 1:
The patent discards B-Frames (bidirectional frames) from the video stream temporarily during channel changes. Since B-Frames are not reference frames and can be reconstructed by the decoder using previous and future frames, their selective discarding reduces the data transmission rate during channel switching without permanently losing video quality. This resolves the contradiction by enabling faster channel changes without requiring additional DSL capacity.
Solution Approach 2:
The patent dynamically changes the video stream parameters during channel changes by adjusting which frames are transmitted. Specifically, it modifies the frame transmission pattern to exclude B-Frames during the transition period, then returns to normal transmission afterward. This parameter change enables rapid channel switching while maintaining standard DSL capacity requirements.
2Loss of time
If the network device transfers 2 seconds of HDTV delay to the decoder, then multicast stream can be joined, but transmission rate must increase to 8 Mbps from 6 Mbps
Solution Approach 1:
The patent applies frame discarding to reduce the transmission burden during delay transfer. By removing B-Frames from the stream, the effective data rate during the 2-second delay transfer period is reduced, eliminating the need to burst at 8 Mbps while still achieving the necessary delay transfer to synchronize with multicast streams.
3Productivity
If additional capacity is reserved on the DSL line for rapid channel changes, then channel switching is faster, but the DSL serving area is reduced
Solution Approach 1:
The patent changes the transmission parameters dynamically during channel switches by discarding B-Frames temporarily. This allows the system to achieve rapid channel switching without reserving additional DSL capacity, thereby maintaining the full DSL serving area while improving channel switching efficiency.
Data Source
AI summary
A system, method and computer readable medium operable to move a video delay from a network video queue to a decoder video queue by discarding at least one video frame in a network video queue, thus moving video frames deeper in the queue forward in time. As such, rapid channel changing is provided without continuous unicasting, or temporarily transmitting at faster than the nominal rate, thereby alleviating strain on the network.