The invention relates to real-time handling of data in more in particular, estimation of time needed to retrieve frames for video rendering, taking fragmentation of frames into account. Especially for data retrieval for trick-play, this is non-trivial, as it is not known on beforehand whether the frames to be retrieved are fragmented. Retrieval of non contiguously fragmented frames takes at least twice as much time as retrieval of a non-fragmented frame. The invention provides various advantageous embodiments, taking into account that when allocation units are substantially larger than the size of frames to be retrieved. An embodiment of the invention provides a method for accurate retrieval time estimation when trick play speed, allocation unit size, frame size and logical data distance between frames to retrieve is known.