fig1 shows an embodiment of the multimedia entertainment system according to the invention . the system comprises a server side 5 , provided at the edge of a communication network 10 , and a client side 20 , provided in the subscriber terminal . server 5 , also referred to as an ip edge , receives encoded multimedia entertainment streams form a head - end 1 in the network 10 and provides the content over transport streams 18 to clients 20 upon request . relevant to the invention the ip edge 5 includes an multimedia control mechanism ( mcm ) 12 that sends out messages on a periodic basis to query which clients ( subscriber terminals 20 ) wish to receive multicast traffic . the messages 16 generated by the clients , called membership reports or requests , provide requests to join or leave specific multicasts and indicate the subscriber client multicast address . mcm 12 examines the reports and either enables or disables forwarding of that particular multicast . various listening mechanisms may be used at the ip edge 5 for detecting a channel change request from the clients , such as a unicast listening http mechanism , ( i . e . listening mechanism 12 may be a igmp snooping interface , a http / javascript interface which is also available on all set - top boxes , or an rtsp mechanism . advantageously , if detection of requests is implemented using igmp snooping , the solution according to the invention will support multicast security enhancements and would time - out clients that no longer respond to igmp queries . as well , all clients conforming to level - 2 of the ip multicasting specification require today igmp ( version 2 or higher ). clients 20 represent any type of subscriber terminal ( st ) enabled with a display 27 for viewing the multimedia entertainment content received from server 5 , such as e . g . a subscriber terminal box , a cd or dvd player , a pc , etc . as well known , a st 20 includes a decoder 24 for converting the content of the elementary streams of multimedia content streams into the respective audio and video information , a multimedia application 21 that enables the user to view and select the content of interest from the server , and an ordering system 25 that transmits membership requests 16 for reception by the listening mechanism 12 of the ip edge 5 . relevant to this invention , st 20 includes an input buffer 22 for storing the input data until a milestone is detected , and a psi ( program and system information ) controller 23 that detects the milestones in the stream and instructs the decoder to start decompressing / decoding data . as indicated above , the program and system information includes a program association table ( pat ), the program map tables ( pmt ) and conditional access tables ( cat , not shown ). the pat includes data that the decoder uses to determine which programs exist in the respective transport stream . pat points to a number of pmts ( one per program ), which , in turn points to the pid of the video , audio , and data elementary streams of a respective program carried by the stream . as indicated above , delivery of a / v streams commences as soon as ( but not until ) the decoder receives critical milestone information required to decode the a / v stream . since program guide and system information is send to the subscriber terminal before the respective content , the pid for the requested channel is already known at terminal 20 , so that the decoder does not need to establish the correspondence between the pid of the of the elementary streams to re - assemble the respective stream . thus , unit 23 retrieves the system information from the streams buffered in the input buffer 22 for each elementary stream in the respective transport stream . the psi controller 23 includes a pid change unit 26 that modifies the values of the program identifier ( pid ) of the audio and video packets of the elementary streams of a respective transport stream to a common pid value , already known at the decoder . in other words , with the present invention , all audio , video and other related data in the respective transport stream are referenced by the same pid . for example , if a pid of “ 0 × 10 ” is used to represent the audio data , then every other elementary stream in a transport stream that contains the respective audio data always uses the same “ 0 × 10 ” pid . thus , when the decoder is first initialized , it does a search for a pat / pmt table to determine the audio and video pid &# 39 ; s that it will use to identify the different elementary streams for proper decoding — these audio and video pid &# 39 ; s are controlled by the pid change unit . normally , when a channel change takes place , the decoder must stop and re - start , which causes the decoder to begin the whole searching process again . with this invention , the decoder only searches once ; therefore , on a channel change , the pid change unit 26 forces all video / audio elements to be the same pid values as when the decoder was first initialized . on initialization , pre - defined pid values that are in the first joined multimedia stream may be used to replace the pid values on all channels that are joined after that . alternatively , pre - selected pid values may be used , and the pid of any new channel that the client joins may be changed to the selected pid values , even on the first joined channel . this causes the decoder to stay in a decode mode , which eliminates the need to stop and restart the decoder and eliminates the need for the decoder to determine if the pid values have changed . this information is processed separately and is sent to the decoder 24 before sending any other data . this enables the decoder to immediately select the packets in the requested channel and decompress correctly the data . since the pid values of the elementary streams of a transport stream are always the same , the decoder always stays in a run state , allowing only the content to change and decreasing the delay to switch between different a / v streams . by allowing the decoder to stay in a run state when switching between the streams , channel change times can be reduced significantly . it is to be noted again that the invention is not restricted to mpeg streams , but is applicable to any transport stream having a significant milestone corresponding to a full picture and characterized in that stream rendering cannot commence until certain milestone packets ( or key structures ) have been received , which indicate where the audio , video , and other data can be found based on the pid value associated with the elementary streams . multicast mpeg2 transport stream is an example of such stream , containing audio and video elementary streams , program specific information ( psi ) and other data .