在网络传输能力不足以实时传输MPEG-2码流时，接收端的图象恢复质量会因为在网络传送中不可避免的、随机的数据丢失而严重下降，为了解决这一问题，提出了一种基于主动抛弃的MPEG-2 TS流速率控制算法，即在原始码流输送到网络前，根据预测的网络传输阻塞状况，预先主动抛弃部分不太重要的数据，从而使实际输出码率与可用网络带宽匹配，以保护重要数据和改善接收端的图象恢复质量，并提高网络带宽的利用率，经实验测试证明，此算法简单、实用、有效、且接收端的图象恢复质量比任凭网络随机丢失的情况有明显改善。

Because there may be bit error and packet loss in network transmission, the network between an real time MPEG 2 encoder and decoder would bring impairment to the bitstream especially when the network is heavily loaded. The video quality would be degraded when the bitstream is corrupt or broken. In this paper, a MPEG 2 TS stream rate control algorithm based on active packet discarding is proposed to resolve this problem. It test the network traffic by monitoring MPEG 2 stream transmission buffer, and discards some not so important TS packet of the MPEG 2 bitstream actively according to the test result to reduce bit rate before pouring data into network. When data loss is inevitable, the difference between active discarding and data loss in the network is that we can control which part of data should be lost under active discarding, and we con't know which part of data will be lost if we leave the loss control to network. Experiment results demonstrated that this algorithm is simple, useful and resultful for real time MPEG 2 TS stream transmission in network. It is adaptive to network traffic, the receiver end video quality is improved obviously, especially when the network is heavily loaded.