Region-Based Rate Control for H.264/AVC for Low Bit-Rate Applications

Abstract

Rate-control plays an important role in video coding. However, in the conventional rate-control algorithms, the number and position of Macroblocks (MBs) inside one basic unit for rate-control is inflexible and predetermined. The different characteristics of the MBs are not fully considered. Also, there is no overall optimization of the coding of basic units. This paper proposes a new region-based rate-control scheme for H.264/AVC to improve the coding efficiency. The inter-frame information is explored to objectively divide one frame into multiple regions based on their rate-distortion behaviors. The MBs with the similar characteristics are classified into the same region, and the entire region instead of a single MB or a group of contiguous MBs is treated as a basic unit for rate-control. A linear rate-quantization stepsize model and a linear distortion-quantization stepsize model are proposed to accurately describe the rate-distortion characteristics for the region-based basic units. Moreover, based on the above linear models, an overall optimization model is proposed to obtain suitable Quantization Parameters (QPs) for the region-based basic units. Experimental results demonstrate that the proposed region-based rate-control approach can achieve both better subjective and objective quality by performing the rate-control adaptively with the content, compared to the conventional rate-control approaches.

Region-of-interest based rate control algorithm for H.264/AVC video coding

“…Thirdly, the preliminary QP value is determined by quadratic RD model and four constraints are adopted to adjust the QP value. 4) RBUR: RBUR algorithm proposed in [5] describes a linear rate-quantization (R-QS) model and linear distortion-quantization (D-QS) model and the overall optimization model is established based on the proposed two linear models, which obtain the initial values of the linear model by the statistical properties of video signals. 5) RCAMC: RCAMC algorithm adopts different bit allocation strategies for the ROI and NROI areas based on the video texture characters.…”

“…Therefore, it is necessary to break up a frame according to people's focus. There are lots of existing methods [5,7,13,16,25] to determine region. Their thoughts are divide an image into ROI and NROI.…”

Region-of-interest-based rate control scheme for high-efficiency video coding

“…In [6], a complete ROI-based controller is proposed. The scheme includes five steps, starting with region devising using the R-D characteristics of each macroblock.…”

“…Thus, the same factor is used to refine their allocated budget, while the cost of inter pictures is determined according to different weights w p for the different hierarchical levels. At the frame level, an initial budget is allocated per frame, using T g computed in (6) and the bit cost of already coded pictures in the current GOP T g ,…”

“…These techniques considered the R-Q linear model [5,6] or the quadratic RC model [3,4] and are useful for H.264/AVC implementations. Meanwhile, the new HEVC standard has been recently finalized by ITU-T and ISO/IEC [7] and many works have focused on rate control and developed new R-Q schemes for it.…”