Multi-Layer Rate Control for Video Transmitters
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Solution Overview
Problem
Conventional video processing systems face challenges in managing bit allocation across multiple codecs to maintain a constant bit rate and prevent buffer overflow/underflow, especially when dealing with different frame types and codecs, which affects video transmission efficiency.
Innovation Solution
A multi-layer rate control system that allocates target bits to frames based on their type and codec, using a quantization parameter (QP) adjusted by a PID control system to manage bit errors and buffer conditions, ensuring a constant overall bit rate across multiple video streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple codecs with different frame types are used to increase video transmission flexibility, then video transmission efficiency is improved, but bit rate control becomes difficult causing buffer overflow/underflow
Solution Approach 1:
The patent dynamically adjusts the quantization parameter (QP) based on buffer status and frame type to control bit rate. Different QP adjustment strategies are applied for different frame types (I, P, B frames) and buffer conditions, enabling flexible adaptation while maintaining stable bit rate control across multiple codecs
Solution Approach 2:
The patent implements a feedback mechanism where the buffer status is continuously monitored and used to adjust the QP parameter for subsequent frames. This closed-loop control ensures that bit rate adjustments are made in response to actual buffer conditions, preventing both overflow and underflow while maintaining video quality
2Stability of the object's composition
If target bits are allocated based on frame type and codec to improve bit rate constancy, then buffer overflow/underflow is prevented, but system complexity increases
Solution Approach 1:
The patent applies different bit allocation strategies and QP adjustment rules for different frame types (I-frames, P-frames, B-frames) and different codec types. This localized approach allows optimal bit rate control for each frame type while maintaining overall bit rate constancy, without requiring a complete redesign of the entire system
Solution Approach 2:
The patent divides the bit rate control process into multiple layers: frame-level bit allocation based on frame type, macroblock-level QP adjustment, and buffer-level feedback control. This segmentation allows each layer to handle specific aspects of rate control independently, reducing overall system complexity while achieving stable bit rate
Data Source
AI summary
A video transmitter comprising a plurality of encoders may be operable to determine, for a transport stream, a constant overall number of bits per time interval corresponding to a frame in the transport stream. For each time interval corresponding to a start and an end of encoding of each of frames using each of the encoders, the video transmitter may allocate a target number of bits to each of the frames to achieve the constant overall number of bits. The allocation of the target number of bits may be based on frame types of the frames and CODEC types of the encoders, where the allocated target number of bits for each of the frames meets buffer overflow/underflow requirements associated with each of the encoders. A quantization parameter (QP) may be calculated and adjusted at each of one or more layers for generating an actual number of bits during encoding.