Video Coding Inter-Coded Recovery Frame LTR
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Solution Overview
Problem
Conventional video codec systems face significant bitrate overshoots and increased source coding distortion when recovering from lost frames, particularly in negative feedback schemes, as they often require sending fully intra-coded key-frames, which can lead to severe distortions and inefficient bitrate usage.
Innovation Solution
The introduction of Long Term Reference (LTR) frames allows for the generation and transmission of inter-coded recovery frames based on the Last Known Good frame, reducing bitrate requirements by enabling decoding even when a reference frame is lost, without the need for fully intra-coded key-frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fully intra-coded key-frames are sent for frame loss recovery, then decoding can proceed without reference frames, but bitrate consumption increases significantly and source coding distortion increases
Solution Approach 1:
The patent applies local quality by differentiating between different types of frames and their coding modes. Instead of uniformly using intra-coded key-frames for all recovery scenarios, the system selectively uses inter-coded frames with reference to the Last Known Good frame for specific recovery situations. This localized approach optimizes bitrate usage by applying the appropriate coding strategy (intra or inter) based on the specific loss scenario and frame type, thereby reducing overall bitrate consumption while maintaining recovery capability.
2Reliability
If fully intra-coded key-frames are sent for frame loss recovery, then decoding can proceed independently of lost frames, but source coding distortion increases severely
Solution Approach 1:
The patent changes the parameter of reference frame selection by introducing the concept of Last Known Good frame as a reference for inter-coded recovery frames. Instead of always using intra-prediction (which has high distortion), the system switches to inter-prediction with reference to a previously decoded good frame when appropriate. This parameter change in the coding mode selection reduces source coding distortion while maintaining the ability to recover from frame losses.
3Quantity of substance
If inter-coded frames are used with reference to Last Known Good frame, then bitrate consumption is reduced, but decoding dependency on reference frames increases
Solution Approach 1:
The patent applies preliminary action by pre-identifying and designating the Last Known Good frame as a reference frame before it is needed for recovery. The system maintains tracking of the last successfully decoded frame and prepares it for potential inter-coding operations. This preliminary preparation reduces decoding complexity at the moment of recovery, as the reference frame is already identified and available, rather than requiring complex searches or decisions during the recovery process.
Data Source
AI summary
A transmitting device for generating a plurality of encoded portions of a video to be transmitted to a receiving device over a network configured to: receive an error message over a feedback channel from the receiving device indicating at least one of said plurality of encoded portions that has been lost at the receiving device; encode a recovery portion responsive to said receiving said error message; and transmit said recovery portion to the receiving device over said network; wherein said error message includes information pertaining to a decoded portion successfully decoded at the receiving device and said recovery portion is encoded relative to said decoded portion.