Multi-Pass Video Encoder Scene-Based Bit Allocation
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Solution Overview
Problem
Existing video encoding technologies face challenges in correcting hypothetical reference decoder conformance errors, particularly buffer underflow errors, which require re-encoding and can lead to additional errors in the bitstream.
Innovation Solution
A multi-pass encoder system that determines bit consumption in the first pass and controls bit allocation in the second pass to prevent buffer underflow and overflow conditions, encoding pictures into multiple bitstreams on a scene basis, ensuring compliance with hypothetical reference decoder requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single-pass encoder is used, then the encoding process is simple and fast, but buffer underflow and overflow errors cannot be prevented
Solution Approach 1:
The encoding process is divided into multiple passes (analysis pass and encoding pass) with different functions. The analysis pass computes bit consumption and buffer status, while the encoding pass performs actual encoding with corrected bit allocation, separating detection and correction functions to resolve the contradiction between speed and reliability
Solution Approach 2:
The encoder performs a preliminary analysis pass before the actual encoding to determine bit consumption and identify potential buffer underflow/overflow errors. This preliminary action allows the system to plan and adjust bit allocation in advance, preventing conformance errors while maintaining efficient encoding
2Reliability
If re-encoding is performed to correct buffer underflow errors, then conformance errors are corrected, but additional errors may occur in different places in the bitstream
Solution Approach 1:
The encoder uses feedback from the analysis pass about buffer status and bit consumption to adjust bit allocation in the encoding pass. This feedback mechanism allows the system to correct conformance errors in a single encoding process rather than requiring iterative re-encoding, reducing overall process complexity
Solution Approach 2:
The patent introduces an intermediate data structure (scene-based bitstream organization with buffer status tracking) that acts as a mediator between the encoding process and HRD conformance requirements. This intermediary structure allows the encoder to maintain conformance without complex iterative re-encoding processes
3Reliability
If multi-pass encoding with scene-based organization is used, then HRD conformance is ensured, but the encoding process becomes more complex
Solution Approach 1:
The video sequence is segmented into scenes, and each scene is encoded as a separate bitstream with independent buffer status tracking. This segmentation allows the complex HRD conformance requirements to be managed at the scene level rather than requiring complex global coordination across the entire bitstream
Solution Approach 2:
The encoder dynamically adjusts encoding parameters (bit allocation, picture quality) based on buffer status and HRD conformance requirements determined during the analysis pass. These parameter changes ensure conformance while managing the complexity of the multi-pass encoding process through adaptive control
Data Source
AI summary
A method and apparatus are disclosed and described for providing hypothetical reference decoder conformance error detection. The apparatus includes a multi-pass encoder (200) for encoding pictures in a video sequence. The pictures are encoded in a first pass to determine a bit consumption of each picture, and a bit allocation is controlled during the encoding of the pictures in at least a second pass responsive to satisfying requirements for a subsequent decoding of the bitstream. The requirements relate to preventing at least one of underflow and overflow conditions in a buffer during the subsequent decoding. The bit allocation is based on the bit consumption determined in the first pass and buffer parameters. The pictures are encoded in at least the first and second passes into a plurality of bitstreams on a scene-basis such that any of the pictures belonging to a same scene are respectively encoded in a same one of the bitstreams.