Toward optimal video transcoding

Real-time multimedia applications often require efficient bitrate reduction. This is mainly done by requantization, usually in the DCT domain. This work introduces theoretical rate-distortion analysis that allows for straightforward selection of the quantization step needed to achieve a given bit-rate. The analysis is based on the Laplace-like distribution of DCT coefficients in the transform domain and on the structure of the quantizers commonly used in video and image coding. We show that the proposed transcoding design achieves significant compression at relatively low distortion, while keeping the computational complexity very low, allowing for real-time implementation.