MPEG stream switching process

Process for switching from an old MPEG data stream to a new MPEG data stream so as to obtain a switched stream, the point of exit in the old stream corresponding to the end of a data packet of a TS stream relating to the last image of the old stream and the point of entry in the new stream corresponding to the start of a data packet relating to the first image of the new stream,

• wherein
• PCRold (Program Clock Reference) and PCRnew being the clock instants relating respectively to the point of exit and point of entry, DTS_next_AUold (Decoding Time Stamp) and DTS_first_AUnew corresponding respectively to the calculated instant of decoding of the image following the last image of the old stream and the calculated instant of decoding of the first image of the new stream, a comparison is performed between the expressions
• DTS_next_AUold−PCRold and DTS_first_AUnew−PCRnew
• and,
• if:
• DTS_next_AUold−PCRold<DTS_first_AUnew−PCRnew,
• then,
• in a first step, the data of one or more last images of the old stream and/or one or more first images of the new stream are replaced by data of one or more new pre-encoded images of which the number is smaller so that the new value of PCRold and/or PCRnew thus obtained satisfies the relation:
• DTS_next_AUold−PCRold≧DTS_first_AUnew−PCRnew,
• in a second step, if there is inequality, TS stuffing packets are inserted between the point of exit and the point of entry so as to make the decoding instants DTS_next_AUold and DTS_first_AUnew coincide,
• if:
• DTS_next_AUold−PCRold>DTS_first_AUnew−PCRnew,
• TS stuffing packets are inserted between the point of exit and the point of entry so as to make the decoding instants DTS next AUold and DTS_first_AUnew coincide.