基于CPLD芯片的视频图像码率控制方法研究

Research on Video Image Bit Rate Control Method Based on CPLD Chip

摘要:

针对小波视频码率控制方法缓冲器容量有限，存在控制精准误差大的问题，提出了基于CPLD芯片的视频图像码率控制方法研究。依据基于CPLD芯片的视频图像码率控制框图可知，该码率控制方法是由CPLD芯片视频图像灰度增强、编码码率控制、视频质量控制与主动跳帧控制四个模块组成的。运用Philips公司的9位视频输入处理器sAA7113芯片解码视频，输出达到ITU656标准的YUV 4：2：2格式的数字视频信号。统一视频信号格式，利用灰度的线性变换的方式增强图像灰度，借助Verilog HDL描述CPLD执行算法。依据固定编码比特率和固定图像质量之间关系，获取编码特性，并计算缓冲区和编码帧目标比特数，依据当前渲染到纹理值，统计报文丢失率，由此实现视频图像编码码率控制。为了扩充缓冲器容量，对视频质量和主动跳帧进行控制，使缓存满度的减小不会导致控制器无法精准调节后续帧量化参数。由实验结果可知，该方法最小控制误差为0.07，能够有效提高视频质量。

Abstract:

Aiming at the problem of the limited buffer capacity of the wavelet video bit rate control method and the large control accuracy error, a method of video image bit rate control based on the CPLD chip is proposed. According to the CPLD chip-based video image bit rate control block diagram, it can be known that the code rate control method is composed of CPLD chip video image gray level enhancement, encoding bit rate control, video quality control, and active frame skip control. Use Philips 9-bit video input processor sAA7113 chip to decode video and output digital video signals in YUV 4: 2: 2 format up to ITU656 standard. Unify the video signal format, use the linear transformation of gray to enhance the gray of the image, and describe the CPLD execution algorithm with the help of Verilog HDL. According to the relationship between the fixed encoding bit rate and the fixed image quality, the encoding characteristics are obtained, and the target bit number of the buffer and the encoding frame is calculated. According to the current rendering to the texture value, the message loss rate is counted, thereby implementing the video image encoding bit rate control . In order to expand the buffer capacity, the video quality and active frame skip are controlled so that the reduction of the buffer fullness will not cause the controller to accurately adjust the quantization parameters of subsequent frames. The experimental results show that the minimum control error of this method is 0.07, which can effectively improve the video quality.