Audio as a support to low bit rate multimedia communication

This paper provides a reduced complexity version of the G.723.1 dual rate speech coder for multimedia communication transmitting at 5.3 and 6.3 kbit/s. This version is bit stream interoperable with the full version, i.e. a reduced complexity encoder may be used with a full implementation of the decoder. This simplified G.723.1 has been applied in a multimedia system, ITU-T H.324, that is implemented based on the PC platform of Windows95. The H.324 are the terminals for low bit rate multimedia communication, utilizing V.34 modems operating over the general switched telephone network (GSTN). The H.324 terminals include the H.223 multiplex, H.245 control, H.263 video codec, and the G.723.1 audio codec. The bottleneck for this system is the enormous computing quantity and current PCs speed. The video codec and the audio codec account for most of the computing quantity. Intel MMX assembly of the Pentium can be used effectively to reduced the computing quantity for the H.263 video codec, but it does not work for G.723 audio, as audio is represented in a different way from video. It is difficult to reduce the computing complexity of G.723. This paper provides a program optimized and reduced complexity version of the G.723.1 audio codec. This version is a bit stream interoperable with the full version. A real-time test shows, the computing complexity of this optimized and simplified version of G.723.1 audio codec has been 33% of the full version. The quality of reconstructed audio in this version is almost the same as the full version.