Bitstream Bit Count Estimation for Constant Rate Video Encoding
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Solution Overview
Problem
Existing video encoding techniques, such as CABAC, face challenges in real-time applications due to their computational demands and serial encoding processes, which are impractical for maintaining a constant bit rate in variable bit rate (VBR) or constant bit rate (CBR) bitstreams, especially in scenarios with high motion video scenes.
Innovation Solution
The proposed solution involves a macroblock encoder and transcoder system that estimates bit counts using context-adaptive variable-length coding (CAVLC) and binary arithmetic coding (CABAC), allowing for real-time conversion of bitstreams to maintain a constant bit rate by dynamically adjusting bit rates based on estimated bit counts, thereby optimizing rate-distortion costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CABAC encoding is used to achieve high compression efficiency, then manufacturing precision is improved, but device complexity increases and real-time processing becomes impractical
Solution Approach 1:
The patent segments the encoding process into two distinct parts: a first entropy encoder that performs simple, fast encoding suitable for real-time processing, and a second entropy encoder that performs complex CABAC encoding for high compression efficiency. This segmentation allows each encoder to be optimized for its specific function, resolving the contradiction between speed and compression efficiency.
Solution Approach 2:
The patent introduces an intermediary component that estimates bit counts for the second entropy encoder based on characteristics of the first entropy encoder's output. This intermediary estimation mechanism allows the system to plan and control the bit rate contribution of the complex CABAC encoding without actually performing the complex encoding in real-time, thus resolving the contradiction between real-time processing capability and high compression efficiency.
2Reliability
If serial encoding processes are used to maintain constant bit rate, then reliability is improved, but productivity decreases due to computational demands
Solution Approach 1:
The patent divides the bitstream generation into parallel paths: a first entropy encoder that operates in real-time with simple encoding, and a second entropy encoder that performs complex CABAC encoding offline or with minimal impact on real-time constraints. This segmentation maintains reliable constant bit rate control through the second encoder while the first encoder ensures real-time processing capability.
Solution Approach 2:
The patent implements preliminary bit count estimation for the second entropy encoder based on characteristics of the first encoder's output. This preliminary action allows the system to plan and control the bit rate contribution of the complex CABAC encoding in advance, enabling real-time constant bit rate maintenance without the computational burden of performing full CABAC encoding in real-time.
3Loss of information
If complex entropy encoding is used to reduce bitstream size, then loss of information is reduced, but loss of time increases due to serial processing requirements
Solution Approach 1:
The patent segments the encoding workload into a first entropy encoder that processes data quickly with simple encoding methods, and a second entropy encoder that applies complex CABAC encoding to achieve high compression efficiency. The segmentation allows the time-critical portion to be processed quickly while the compression-optimized portion can be processed with more time flexibility.
Solution Approach 2:
The patent introduces an intermediary bit count estimation mechanism that predicts the output size of the second entropy encoder based on characteristics of the first encoder's output. This intermediary estimation allows the system to achieve high compression efficiency through CABAC encoding without requiring the complex encoding to complete in real-time, thus reducing the time loss associated with serial processing of complex encoding operations.
Data Source
AI summary
Examples of methods and apparatuses for estimating bit counts of a bitstream are described herein. An entropy encoder may include a bitstream encoding module and a bit count estimation module. The bitstream encoding module may be configured to encode a plurality of syntax elements according to a first encoding technique. The bit count estimation module may be configured to provide estimated bit counts for encoding the plurality of syntax elements according to a second encoding technique. In at least one embodiment, the bitstream encoding module may be further configured to encode the plurality of syntax elements based on the estimated bit counts.