一种低延迟限制下H.264码率控制算法

A rate control scheme for H. 264 under low delay constraint

对于实时、双向视频通信而言,减少传输时所造成的延迟是十分重要的。本文针对H.264视频压缩编码标准,提出了一种在低延迟条件下,仍可维持高画质并避免缓存区溢出的码率控制算法。鉴于I帧量化参数的选择对于整个GOP编码比特及失真的影响,本文通过对整个GOP的预测码率和失真做率失真优化,来选择可以平衡整个GOP编码量和失真的量化参数。同时增加一个主动跳帧策略,在缓存区未达饱和状态时,仍主动跳过一些并不重要的图像,而留出区空间使那些相对重要的图像可以保留。实验结果表明,在低延迟条件下,本文的方法不论在避免跳帧和维持画质方面均高于JVT新近采纳的JVT-H017提案。

It is very important to minimize the end-to-end delay for transmitting video data in real-time, two way video communications. In this paper, we propose a rate control scheme under low time delay constraint for H.264 standards. Since encoding the I- frame by different QP will generate different rate and distortion for the GOP, we perform RDO for the prediction bits and distortion of the GOP to find the best QP of I frame which could gain the tradeoff between the rate and distortion of this GOP. We also introduce a scheme to charge the encode buffer, allowing some less important frames to be skipped even the buffer is not full, thus these important frames could have enough space to be encoded. The experiments show that compare to the JVT-H017 scheme, our proposal gained higher PSNR with less frame skipping.