Method for the processing of multimedia data in a reception device comprising an interface to a first network and an interface to a second network, comprising the following steps of: - receiving, from the first network, through a first transport protocol, a first flow comprising first multimedia data, and temporal synchronization data related to a timeline for content rendering, said temporal synchronization data being transported in auxiliary data packets synchronized with the first multimedia data using a synchronization protocol specific to said first protocol; - receiving, from the second network, through a second transport protocol, a second flow comprising second multimedia data and the temporal synchronization data related to the timeline for content rendering, said temporal synchronization data being transported in auxiliary data packets synchronized with the second multimedia data using a synchronization protocol specific to said second protocol said second multimedia data being pre-loaded upon request of said reception device to enable the reception device to render it synchronously with the first multimedia data; - synchronizing the rendering of said first and second multimedia data by using temporal synchronization data related to the timeline for content rendering; said method comprising the steps of, prior to rendering said first flow: - receiving, from the first network, countdown information indicating when the timeline for content rendering is to begin, said countdown information being transported in said first flow; and - issuing, based on said countdown information, said request to receive said second multimedia data before the beginning of the timeline for content rendering, so that said second multimedia data is rendered synchronously with said first multimedia data. - receiving, from the first network, through a first transport protocol, a first flow comprising first multimedia data, and temporal synchronization data related to a timeline for content rendering, said temporal synchronization data being transported in auxiliary data packets synchronized with the first multimedia data using a synchronization protocol specific to said first protocol; - receiving, from the second network, through a second transport protocol, a second flow comprising second multimedia data and the temporal synchronization data related to the timeline for content rendering, said temporal synchronization data being transported in auxiliary data packets synchronized with the second multimedia data using a synchronization protocol specific to said second protocol said second multimedia data being pre-loaded upon request of said reception device to enable the reception device to render it synchronously with the first multimedia data; - synchronizing the rendering of said first and second multimedia data by using temporal synchronization data related to the timeline for content rendering; - receiving, from the first network, countdown information indicating when the timeline for content rendering is to begin, said countdown information being transported in said first flow; and - issuing, based on said countdown information, said request to receive said second multimedia data before the beginning of the timeline for content rendering, so that said second multimedia data is rendered synchronously with said first multimedia data.