cal wireless environments, and cost of implementation. A number of standardized media types for text, voice, audio, images and video are listed below: XHTML basic: XHTML Basic is designed for web clients that do not support the full set of XHTML features, for example mobile phones, PDAs, pagers and set-top boxes. AMR: the AMR voice codec (3GPP TS 26.090) encodes narrow-band (4 kHz 'telephony' bandwidth) voice using one out of eight rates between 4.75 kbit/s and 12.2 kbit/s. The media type is well suited to all voice and news clips. AMR was standardized by ETSI in 1998. AMR will be further described in Chapter 8. AMR wideband: the AMR wideband voice codec (3GPP TS 26.190) encodes wideband (8 kHz audio bandwidth) signals using one out of nine rates between 6.60 kbit/s and 23.85 kbit/s. The media type is well suited to all kinds of voice and audio clips, and provides high-quality sound. AMR wideband was standardized by 3GPP in 2001. MPEG-4 AAC-LC: the low-complexity version of the Advanced Audio Codec of MPEG-4 provides a range of bit rates and quality levels. The media type is well suited to high-quality audio at bit rates of 64 kbit/s and above. MPEG-4 AAC was standardized by ISO/IEC in 1999. JPEG: the JPEG compression provides lossy compression of typically photographic images with a compression ratio of 4:1 to 30:1 leading to typical mobile compressed file sizes of 5-20 kbytes. JPEG was standardized by ISO/IEC in 1992. GIF: A format for colour raster images that is among the most widely used formats for graphics compression. While GIF87a supports only still images, GIF89a supports simple animation sequences. H.263: the H.263 standard supports video compression for applications, such as video conferencing, video telephony, and video streaming. H.263 aims particularly at video coding for low bit rates (typically 20-30 kbit/s and above). The H.263 baseline was Services approved in 1995, with a new version including the profile and level specifications from 2000. MPEG-4 visual: the simple profile is suited for mobil