Requantization transcoding in pixel and frequency domain for intra 16x16 in H.264/AVC

In the context of Universal Multimedia Access, efficient techniques are needed for the adaptation of video content. An important example is the reduction of the bitrate in order to satisfy the bandwidth constraints imposed by the network or the decoding capability of the terminal devices. Requantization transcoding is a fast technique for bitrate reduction, and has been successfully applied in previous video coding standards such as MPEG-2. In this paper, we examine requantization in H.264/AVC, focusing on the intra 16 x 16 prediction modes. Due to the newly introduced coding tools in H.264/AVC, new techniques are needed that are able to lower the bitrate at a minimal quality loss. We propose two novel architectures, one in the pixel domain and one in the frequency domain, that reuse the information from the incoming bitstream in an efficient way, and perform approximately equally well as a cascade of decoder and encoder. Due to their low computational complexity, the introduced architectures are highly suitable for on-the-fly video adaptation scenarios.