A standalone video communication system for wire and wireless applications

We present a low bit rate, standalone and portable video communication system for wire and wireless applications. The video codec is based on H.263, and the audio codec is based on G.723.1. When the application is for wireless the transmission bandwidth is limited to 25 kHz. In order to have reasonably good video and audio quality, the source bit rate is set to 38 kbps. This includes video, audio and synchronization. The bit stream is embedded with 26 kbps for the error protection, resulting in a total of 64 kbps. A 16-QAM is used for the modulation in order to meet the bandwidth requirement. Besides, the RF module is developed for the transmission on the UHF band. An interface for a normal modem is also implemented in the system to make the wired application available. The whole system deployed three general purpose DSP for the real time implementation of video coding, audio coding, channel coding and system control