Visual Media Coding and Transmission

5.4 Bit Allocation and Buffer Control for MVS Encoding Rate Control

(Portions reprinted, with permission, from ICIP' 2007, “Improved feedback compensation mechanisms for multiple video object encoding rate control”, and IEEE CSVT, P. Nunes, F. Pereira, “Joint rate control algorithm for low-delay MPEG-4 object based video encoding”, ©2007 IEEE.)

5.4.1 Problem Definition and Objectives

In delay-constrained constant bit rate (CBR) video encoding, the bit-rate variability is handled through a smoothing bitstream buffer in order to achieve a constant average bit rate measured over short periods of time. In this context, the rate controller is faced with two conflicting goals: (a) keep the bitstream buffer occupancy within permitted bounds, which typically requires finely adjusting the encoding parameters, for example the MB quantization parameter (QP), to produce more/less encoding bits according to the buffer occupancy tendency;(b) adjust the encoding parameters, aiming to maximize the subjective quality of the decoded video, which typically requires slowly changing the QP (both spatially, between adjacent MBs, and temporally, between successive encoding time instants).

To accomplish these goals, the rate controller needs: (a) to properly allocate the available bit rate, taking into account the video data complexity and the proper video buffering verifier mechanism constraints; (b) to compute the coding parameters that would lead to the estimated bit allocations.

As referred to in ...