Abstract-The rate control problem has been extensively studied in parallel to the development of the different video coding standards. The bit allocation via Cauchy-density-based ratedistortion (R-D) modeling of the discrete cosine transform (DCT) coefficients has proved to be one of the most accurate solution at picture level. Nevertheless, in some specific applications operating in real-time low-delay environments, a basic unit (BU) layer is recommended in order to provide a good trade-off between picture quality and delay control. In this paper, a novel BU bit allocation for H.264/AVC is proposed based on a simplified Cauchy probability density function (PDF) source modeling. The experimental results are twofold: 1) the proposed rate control algorithm (RCA) achieves an average PSNR improvement of 0.28 dB respect to a well known BU layer RCA, while maintaining a similar buffer occupancy evolution; and 2) It achieves to notably reduce the buffer occupancy fluctuations respect to a well known picture layer RCA, while maintaining similar quality levels.

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In this paper, a novel rate control algorithm for real-time VBR hierarchical video coding is proposed. The algorithm works at two levels that are called long-and short-term levels. The long-term level aims at ensuring that the bit count does not exceed the maximum allowed amount for a few-second long window. To this end, it considers a sliding window spanning several GOPs, which is shifted on a GOP basis. In doing so, it avoids the potentially sharp adjustments at the end of the GOP that usually happen in non-sliding approaches. The short-term level aims to provide a proper QP adaptation to fit the target bit budget, which is dictated by the long-term level. It also uses a sliding window, which in this case extends over one GOP. The proposed algorithm has been assessed in realistic conditions for a variety of video sequences. It has been compared to both a constant quality and CBR hierarchical approaches, showing an excellent performance in terms of both rate-distortion and PSNR variation.

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Abstract-In this paper, a low-complexity motion-based saliency map estimation method for perceptual video coding is proposed. The method employs a camera motion compensated vector map computed by means of a hierarchical motion estimation (HME) procedure and a Restricted Affine Transformation (RAT)-based modeling of the camera motion. To allow for a computationally efficient solution, the number of layers of the HME has been restricted and the potential unreliable motion vectors due to homogeneous regions have been detected and specially managed by means of a smooth block detector. Special care has been taken of the smoothness of the resulting compensated camera motion vector map to avoid unpleasant artifacts in the perceptuallycoded sequence, by including a final post-processing based on morphological filtering. The proposed saliency map has been both visually and subjectively assessed showing quality improvements when used as a part of the H.264/AVC standard codec at medium-to-low bitrates.