JPEG2000 is the latest image compression standard. One of the most attractive functions which JPEG2000 offers is ROI (region of interest). The ROI region of a human image should usually be on face. In this paper, we present two effective frameworks to convert human images stored in uncompressed format and JPEG2000-compressed format without ROI, respectively, into JPEG2000-compressed format with ROI. Furthermore, a hybrid face localization method is developed, which is well combined with JPEG2000 encoding/decoding procedures. The experimental results show that we can convert the JPEG2000 code stream with partial decode/encode and it has a good face localization performance. The speed of the proposed conversion procedure is faster by two or three times than that of a complete decode/encode conversion procedure

In this letter, we propose a generic and efficient algorithm that can construct both asymmetrical and symmetrical reversible variable-length codes (RVLCs). Starting from a given Huffman code, the construction is based on two developed codeword selection mechanisms, for the symmetrical case and the asymmetrical case, respectively; it is shown that the two mechanisms possess simple features and can generate efficient RVLCs easily. In addition, two new asymmetrical RVLCs are constructed and shown to be very efficient for further reducing the coding overheads in MPEG-4 when operating in the reversible decoding mode.

Reversible variable length codes (RVLCs) have been adopted in emerging video coding standards-H.263+ and MPEG-4-to enhance their error-resilience capabilities (which are important and essential) in error-prone environments. This study proposes an efficient algorithm to construct a symmetrical RVLC from a given Huffman code. In addition, theoretical bounds on the maximum codeword length for fixed-length Huffman codes, and on the optimal average codeword lengths for sources with exponential distribution are provided.