A study on joint rate control for hybrid stereoscopic video codecs

Abstract

In this study a joint rate control scheme is first proposed for a hybrid codec system to encode stereos-copic video, which is based on an optimization framework. The proposed rate control scheme jointly works on the left (MPEG-2) and right (H.264/AVC) encoders for stereoscopic video input by controlling the output bit rates of both encoders in the sense that the sum of the two decoded video qualities is maximized and the quality difference is maintained around a desired level for a given target bit budget at the same time. In optimization, a gradient-based quadratic rate-quantization model and a gradient-based linear distortion-quantization model are proposed and adopted for intra-picture coding. For predictive-picture coding, a qua-dratic rate-quantization model with the MAD in addition to a linear distortion-quantization model with the MAD is considered for finding an optimal solution in the optimization framework. A joint rate control for bidirectional-picture based on a distortion-quantization model is proposed. Novel bit allocation schemes for GOPs, intra-pictures, and predictive-pictures are also discussed. To reduce computational complexity in estimating model parameters and MAD values, predictions based on the exponentially weighted moving average are applied. In addition, MAD prediction for H.264/AVC based on the actual MAD values of MPEG-2 is proposed. From the experimental results, the proposed joint rate control scheme outperforms the independent rate control. For I-frame only coding, the joint rate control scheme achieves about 0.7 dB gain in PSNR, 51.62% reduction in the mean PSNR difference, and 66.75% reduction in the MSE of PSNR difference. For IPPP coding, the proposed joint rate control scheme shows about 0.54 dB gain in PSNR, 78.59% reduction in the mean PSRN difference, and 91.11% decrease in the MSE of PSNR difference. In addition, the abrupt changes in PSNR values of I-frames over GOPs are alleviated by the proposed I-frame joint rate co...