Rate Control Based on Intermediate Description Video adaptation has been proved to be an efficient technique in dealing with various constraints such as bandwidth limitation and user requirement in multimedia applications. However, existing methods including Scalable Video Coding and transcoding cannot get a fine performance when bandwidth constraints exist in various scenarios particularly in realtime applications. In this paper, we propose a novel rate control scheme based on intermediate description. The proposed scheme can provide fast rate control for narrow and timevarying transmission channel in scenarios such as video streaming, video sharing and video on demand. In this scheme, Discrete Cosine Transform (DCT) coefficients distribution is modeled by generalized Gaussian distribution, meanwhile the parameter information of this model is stored as side information for rate control. With the stored parameter information, encoder and transcoder can achieve the target bitrate with low complexity. Furthermore, an initial Quantization Parameter (QP) determination method is also presented to calculate a proper QP for the Instantaneous Decoding Refresh (IDR) picture. Experimental results show that compared with JVTG012 in H.264, the proposed rate control scheme can save more than 85% encoding time and obtain the required bitrate more precisely, meanwhile gains a performance improvement by 0.2dB averagely.

Drift compensated coding optimization for fast bitrate reduction transcoding Bit rate adaptation is one of the basic problems in universal multimedia access. Therefore, in many cases, there exists a strong requirement for a very fast transcoding implementation. Usually, openloop transcoding architecture is the desired solution with the lowest computational complexity. However, severe drift error makes it infeasible to most applications. In this paper, we propose a driftcompensated coding optimization scheme, by which generated bitstreams can be effectively transcoded into lower bitrate by openloop transcoder with little drift propagation. The encoder integrates a virtual openloop transcoder, in which drift error is effectively compensated by suitably adjusting the RD based mode selection and motion estimation for each macroblock. Simulation results show that compared with traditional coding, the proposed mode selection scheme can yield better coding efficiency when rate reduction transcoding to low bitrate occurs. And meanwhile, it does not degrade the coding efficiency in comparison with the normal single layer coding in H.264AVC.