Design and implementation of a two-way real-time communication system for audio over CATV networks

Abstract

In this paper, we design and implement a two-way real-time communication system for audio over cable television (CATV) networks to provide an audio-based interaction between the CATV broadcasting station and CATV subscribers. The two-way real-time communication system consists of a real-time audio encoding/decoding module, a payload formatter based on a transmission control protocol/Internet protocol (TCP/IP), and a cable network. At the broadcasting station, audio signals from a microphone are encoded by an audio codec that is implemented using a digital signal processor (DSP), where the MPEG-2 Layer II audio codec is used for the audio codec and TMS320C6416 is used for a DSP. Next, a payload formatter constructs a TCP/IP packet from an audio bitstream for transmission to a cable modem. Another payload formatter at the subscriber unpacks the TCP/IP packet decoded from the cable modem into audio bitstream. This bitstream is decoded by the MPEG-2 Layer II audio decoder. Finally the decoded audio signals are played out to the speaker. We confirmed that the system worked in real-time, with a measured delay of around 150 ms including the algorithmic and processing time delays.