Virtual Memory Access Bandwidth Verification in Video Coding
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Solution Overview
Problem
The increased memory access bandwidth requirements for motion compensation in HEVC decoders, due to longer interpolation filters, lead to higher decoder costs and inefficiencies, especially as video resolutions increase.
Innovation Solution
Implementing virtual memory access (VMA) bandwidth verification to impose a target VMA bandwidth rate on encoded bit streams, ensuring that the encoder does not generate motion vector fields that result in excessive memory access bandwidth, thereby reducing decoder costs without compromising coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If longer interpolation filters (7-tap or 8-tap for luminance, 4-tap for chrominance) are used in HEVC motion compensation, then inter-prediction accuracy is improved, but motion compensation memory bandwidth requirements increase
Solution Approach 1:
The patent applies preliminary action by performing virtual memory access bandwidth verification during the encoding phase. The encoder calculates the VMA bandwidth rate for each picture using motion vectors and interpolation filter lengths, and compares it against a target rate before encoding the bitstream. This advance verification prevents excessive memory bandwidth consumption in the decoder without requiring actual memory access during decoding.
Solution Approach 2:
The encoder performs self-service by independently verifying its own bitstream's VMA bandwidth compliance. The encoder uses its generated motion vectors and the known interpolation filter configuration to calculate the VMA bandwidth rate, ensuring the encoded bitstream meets the target bandwidth rate without requiring external verification infrastructure.
2Ease of manufacture
If VMA bandwidth verification is implemented to constrain memory access, then decoder costs are reduced, but encoding complexity increases
Solution Approach 1:
The complex verification operation is performed in advance during encoding rather than during decoding. The encoder calculates motion vectors, determines interpolation filter lengths, computes VMA bandwidth rates, and verifies compliance with target rates before bitstream generation. This shifts computational complexity to the encoding phase, enabling simpler, lower-cost decoder implementations.
Solution Approach 2:
The patent introduces an intermediary verification mechanism that acts as a mediator between the encoder and decoder. The VMA bandwidth verification process serves as an intermediate check that ensures encoder output compliance without requiring the decoder to perform complex verification operations, thus simplifying the decoder while maintaining bandwidth control.
Data Source
AI summary
A method is provided that includes determining a target picture virtual memory access (VMA) bandwidth rate, wherein the target picture VMA bandwidth rate indicates a maximum VMA bandwidth rate for motion compensation of a picture, and verifying the target picture VMA bandwidth rate for a compressed video bit stream.