Trick play signal generation for a digital video recorder using retrieved intra-encoded pictures and generated inter-encoded pictures

摘要

The invention relates to the generation of a trick play information stream from a normal play information stream, so that they can be recorded together as a composite information stream on the record carrier, such that upon reproduction in a trick play reproduction mode, an information signal of sufficient quality, eg as regards visibility, can be obtained. One aspect of the invention lies in the generation of GOPs, each GOP comprising an I-frame retrieved from the original normal play information stream, and one or more so-called ‘empty P frames’.(FIG. 12) ;Another aspect of the invention is the requirement of generating GOPs for the trick play information stream that have a constant bitcost per GOP. ;Again another aspect of the invention lies in the retrieval of the I-frame for the trick play information stream from the normal play information. More specifically, an I frame is generated by retrieving from an I-frame included in the normal play information, the DC coefficient of the I frame and a number of AC coefficients from that I frame and generate the I-frame for the trick play information stream therefrom. More specifically, the number of AC coefficients for an I-frame of the trick play information signal depends on the difference between the DC coefficients of two subsequent I-frames in the normal play information from which the I-frame to be generated and the just previously generated I-frame for the trick play information signal have been derived.