Method for transport stream synchronizing in a multiplexer comprising an external corpocessor

System for synchronizing at least one transport stream, referred to as an input stream, into at least one transport stream, referred to as an output stream, each transport stream comprising a plurality of transport packets, said system comprising a multiplexing device to multiplex said at least one input stream and a processing device connected to said multiplexing device to modify at least one input stream before multiplexing, said multiplexing device and said processing device having no common time reference,

• said multiplexing device comprises first reception means to receive said at least one input stream, first determination means to determine an input timestamp for each transport packet of said at least one input stream, transmission means to transmit at least one input stream to said processing device, second reception means to receive said at least one input stream modified by said processing device, second determination means to determine an output timestamp for each transport packet of said at least one input stream, and multiplexing means to multiplex the transport packets of said at least one input stream according to their output timestamp and generate said at least one output stream,
• wherein, to maintain the synchronisation between the transport packets of said at least one input stream and the transport packets of said at least one output stream, the transmission means of the multiplexing device insert, in at least one transport packet of said at least one input stream transmitted to the processing device, an item of synchronisation information based on the input timestamp of said at least one transport packet, and the second determination means determine the output timestamp of at least one transport packet of said at least one input stream modified from the input timestamp of said packet and from said synchronisation information.