Reed Eric C, Lim Jae S
Convergent Syst. Div., Harmonic Inc., White Plains, NY 10601, USA.
IEEE Trans Image Process. 2002;11(8):873-85. doi: 10.1109/TIP.2002.801122.
In conventional bit-rate control, the buffer level is controlled by adapting the quantization step size with a fixed frame rate and spatial resolution. We consider a multidimensional (M-D) bit-rate control where the frame rate, spatial resolution and quantization step size are jointly adapted for buffer control. We introduce a fundamental framework to formalize the description of the M-D buffer-constrained allocation problem. Given a set of operating points on a M-D grid to code a nonstationary source in a buffer-constrained environment, we formulate the optimal solution. The formulation allows a skipped frame to be reconstructed from one coded frame using any temporal interpolation method and is shown to be a generalization of formulations considered in the literature. In the case of intraframe coding, a dynamic programming algorithm is introduced to find the optimal solution. The algorithm allows one to compare operational rate-distortion bounds of the M-D and conventional approaches. We also discuss how a solution can be obtained for the case of interframe coding using the optimal dynamic programming algorithm for intraframe coding by making an independent allocation approximation. We illustrate that the M-D approach can provide bit-rate reductions over 50%. We also show that the M-D approach with limited-lookahead provides a slightly suboptimal solution that consistently outperforms the conventional approach with full-lookahead.
在传统的比特率控制中，通过以固定帧率和空间分辨率调整量化步长来控制缓冲区水平。我们考虑一种多维（M-D）比特率控制，其中帧率、空间分辨率和量化步长联合调整以进行缓冲区控制。我们引入一个基本框架来形式化描述M-D缓冲区受限分配问题。给定一组在M-D网格上的操作点，以便在缓冲区受限环境中对非平稳源进行编码，我们制定了最优解。该公式允许使用任何时间插值方法从一个编码帧重建跳过的帧，并且被证明是文献中考虑的公式的推广。在帧内编码的情况下，引入了一种动态规划算法来找到最优解。该算法允许比较M-D方法和传统方法的运算率失真界限。我们还讨论了如何通过进行独立分配近似，使用帧内编码的最优动态规划算法来获得帧间编码情况下的解。我们表明M-D方法可以提供超过50%的比特率降低。我们还表明，具有有限前瞻的M-D方法提供了一个略次优的解，该解始终优于具有全前瞻的传统方法。
