A novel frame-level bit allocation based on two-pass video encoding for low bit rate video streaming applications

Current rate control schemes in video coding standards do not have efficient frame-level bit allocation due to the limitation of real-time encoding. In this paper, by taking advantage of offline video encoding, we proposed a frame-level bit allocation scheme based on a latest developed rate–distortion (R-D) model, the ρ-domain R-D model [IEEE Trans. Circuits Syst. Video Technol. (2001) 928], for low bit rate streaming applications. Specifically, at the encoder, we code each video sequence twice. In the first pass, we generate the R-D information of video sequences. Then, in the second pass, according to the available channel bandwidth, by exploiting the pre-generated R-D information we are able to implement frame-level bit allocation in an optimal way so that video sequences can be coded at low bit rate with an improved quality. We apply the proposed bit allocation scheme for both offline video coding and rate-reduction transcoding. Experimental results demonstrate the proposed scheme is able to achieve not only reduced average distortion but also much smoother visual quality.