Smoothing of MPEG multi-program video coding for packet networks

In TV broadcast applications, the use of MPEG2 standard allows economies in transmission bandwidth while providing a service with a quality similar or better to the current analogue systems. Interframe and intraframe techniques are used resulting in VBR bit streams, if constant quality is aimed. The number of bits depends on the motion and spatial detail of the video sequences. The compressed picture size differs by a factor up to 8 or more. Different TV programmes present different bandwidth requirements depending on the type of scene being transmitted. Thus buffering is needed to smooth rate fluctuations of encoder's output between pictures. Without smoothing, performance of networks carrying such video traffic can be compromised. The use of dynamic multiplexing schemes to jointly transmit different programmes allows a more efficient distribution of the available channel bandwidth by instantaneously assigning it among video sources according to their needs. The ATM technology provides the mechanisms for flexible allocation of resources and statistical transmission of VBR traffic, while providing the necessary quality of service guarantees to meet the real-time constraints of TV distribution services. This paper proposes the use of dynamic multiplexing algorithms at the user terminal to transmit a number of MPEG2 VBR encoded TV programmes over a VBR ATM channel. It addresses the problem of jointly controlling the channel and several VBR video sources bit rates.