Encoder Bit Rate Control via Dynamic TU Allocation

Solution Overview

Problem

Existing AV1 video encoders face challenges in ensuring that the output bit rate meets the target bit rate due to uncertainties in the number of bits for each coding tree unit (CTU) after encoding.

Innovation Solution

The proposed encoder includes a quantization circuit, a control circuit, and an encoding circuit. The control circuit determines the number of allocated bits for each transform unit (TU) within a CTU based on the remaining bits of encoded TUs, ensuring that the target bit rate is met by adjusting the bit budget for each TU.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If quantization parameters are determined according to target bit rate using encoding rate models, then bit rate control capability is improved, but the inability to determine actual bit consumption before encoding causes bit rate control accuracy to deteriorate

Engineering Contradiction:

Improvebit rate control capabilityVSAvoidbit rate control accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent performs preliminary bit consumption estimation for each TU before actual encoding by analyzing quantized data characteristics. This preliminary action provides advance information about expected bit usage, enabling accurate bit rate control without sacrificing the adaptability of dynamic quantization parameter selection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where actual bit consumption of previously encoded TUs is measured and used to adjust quantization parameters for subsequent TUs. This closed-loop feedback ensures that the target bit rate is met while maintaining the flexibility to adapt to local image characteristics.

Inventive Principle:

Principle #23Feedback

2Productivity

If dynamic quantization parameter selection is used to adapt to local image characteristics, then encoding efficiency is improved, but bit rate control reliability deteriorates due to uncertainty in actual bit consumption

Engineering Contradiction:

Improveencoding efficiencyVSAvoidbit rate control reliability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent performs preliminary bit consumption estimation for each TU before actual encoding by analyzing quantized data characteristics. This preliminary action provides advance information about expected bit usage, enabling accurate bit rate control without sacrificing the adaptability of dynamic quantization parameter selection.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements a feedback mechanism where actual bit consumption of previously encoded TUs is measured and used to adjust quantization parameters for subsequent TUs. This closed-loop feedback ensures that the target bit rate is met while maintaining the flexibility to adapt to local image characteristics.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12212761B2Encoder and associated signal processing method

Publication Date: 2025.01.28 REALTEK SEMICON CORP

AI summary

The present invention provides an encoder including a quantization circuit, a control circuit and an encoding circuit is disclosed. The quantization circuit is configured to generate quantized data corresponding to a CTU according to image data, wherein the CTU comprises at least one TU. The control circuit is configured to determine a number of allocated bits for each TU in the CTU, where the number of allocated bits for each TU is determined based on a sum of remaining bits of the TUs that have been encoded. The encoding circuit is configured to encode each TU to obtain encoded data according to the number of allocated bits of the TU in the CTU.