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

Abstract

A trick play information stream is generated 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, e.g., as regards visibility, can be obtained. GOPs are generated, each GOP including an I-frame retrieved from the original normal play information stream, and one or more so-called 'empty P frames'. Another aspect is the requirement of generating GOPs for the trick play information stream that have a constant bitcost per GOP. Again, another aspect 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 generating 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.