Video telephony in an IP-based set-top box environment

Sammanfattning: This thesis evaluates and shows an implementation of a video telephony solution for network connected set-top boxes based on the SIP protocol for managing sessions. Unlike other video telephony implementations the set-top box does not handle both audio and video, but only video. A separate phone is used to handle audio. To maintain compatibility with other video telephony implementations, which expect a single SIP device with both audio and video capabilities, a mechanism to merge the audio (SIP-phone) and video (set-top box) into a single entity was developed using a back-to-back user agent. Due to the set-top boxes'limited hardware it could be impossible to have video compression and decompression performed by the set-top boxes. However, numerous performance tests of compression algorithms showed that the computational power available in the set-top boxes is sufficient to have acceptable frame rate and image quality in a video telephony session. A faster CPU or dedicated hardware for video compression and decompression would however be required in order to compete with dedicated video telephony systems available today. The implemented video telephony system is based on open standards such as SIP, RTP and H.261, which means interoperability with other video telephony implementations, such as Microsoft's Windows Messenger 4.7, is good.