Rate control algorithm for fast bit-rate conversion transcoding

Abstract

In this paper, a new rate control algorithm is introduced as a solution for fast rate control requirements in transcoding. The specific transcoding problem mentioned in this paper is referred to as bit-rate conversion. For video services in heterogeneous network environments, it is necessary to convert the bit-rate of a compressed video to match it to transmission channels of lower capacity. The transcoding of coded video streams by requantization in the DCT (discrete cosine transform) domain is considered as a promising technique for its low complexity and acceptable picture quality. We carried out extensive simulations for many kinds of video sequences to find a novel R-Q (rate-quantization) model in the requantization process and found a piecewise linearly decreasing model. Exploiting this model we propose an efficient rate control algorithm for fast transcoding. Since the proposed algorithm requires much lower complexity than conventional algorithms and inherently avoids additional steps of implementation for a scene adaptive rate control in the transcoder, it has a significant advantage as a rate control algorithm for transcoding.