Tune-in Time Reduction in Video Streaming Over DVB-H

摘要

A novel method is proposed which minimizes the tune-in time of "channel zapping", i.e. changing from one audiovisual service to another, in IP datacasting (IPDC) over Digital Video Broadcasting for Handheld terminals (DVB-H). DVB-H uses a time-sliced transmission scheme enabling a receiver to turn radio reception off for those time-slices that are not of interest to the user and thus reducing the power consumption used for radio reception. One of the significant factors in tune-in time is the time from the start of media decoding to the start of correct output from decoding, which is minimized when a time-slice starts with a random access point picture such as an independent decoding refresh (IDR) picture in H.264/AVC standard. In IPDC over DVB-H, encapsulation to time-slices is performed independently from encoding in a network element called IP encapsulator. At the time of encoding, time-slice boundaries are typically not known exactly, and it is therefore impossible to govern the location of IDR pictures relative to time-slices. It is proposed that an additional stream consisting of IDR pictures only is transmitted to the IP encapsulator, which replaces pictures in a normal bit stream with IDR pictures according to time-slice boundaries in order to achieve the minimum tune-in delay. Replacing pictures causes a mismatch in the pixel values of the reference pictures between the encoder and decoder and the mismatch error is propagated in the reconstructed video. It has to be ensured that the propagated error is subjectively negligible. Furthermore, the "spliced" stream resulting from the operation of the IP encapsulator should comply with the Hypothetical Reference Decoder (HRD) specification of H.264/AVC. Error propagation caused by the proposed splicing method is analysed and a video rate control system is proposed to satisfy the HRD requirements for the spliced stream. Simulation results show that in addition to fulfilling H.264/AVC compliancy, good average quali- ty of decoded video is achieved with minimum tune-in delay and complexity