Abstract: Based on the analysis of RTP/RTCP protocol, The RTP data format used for MPEG-4 media is analyzed. An implementation scheme of client using MPEG-4 media data is then proposed. Adopting the scheme that video streams are synchronized to audio stream produces a high playback quality of the media player. The thread model and main architecture of the client and are introduced. Applications show that the clients implemented by the scheme have good stability.