Methods for transmitting first packets encapsulated in second packets in a transmission system in which part of the first packets contain a first timing reference for synchronization of a receiver clock and at least part of said second packets contain a second timing reference for reducing transmission jitter of the second packets at the receiver is described. This method provides, at the transmitter, collecting first packets, determining whether a collected first packet contains a first timing reference and triggering transmission of a second packet encapsulating collected first packets including the first packet containing the first timing reference in response to a positive determination.