1. Field of the Invention
This invention relates to a highly efficient coding apparatus for encoding a digital video signal into a format which can be decoded into a video signal compatible with either of two video signal standards having different resolutions.
2. Description of the Prior Art
It has been proposed to provide a television system with a higher resolution than the NTSC system now in practical use. Also, research and development of peripheral equipment such as video tape recorders (VTRs) and video cameras have been done with respect to the proposed higher resolution system. For example, the recording of a high resolution video signal in the form of digital data, for example, has also been proposed. In even the existing standard resolution system, the information amount of a digital video signal is large, and there is a need to record/reproduce a much greater amount of information in the case of a digital video signal. For this purpose, it is common to adopt highly efficient coding for compression of the amount of data to be recorded at the time of recording a high resolution digital video signal.
Conventionally, highly efficient coding methods applicable to a digital video signal with high resolution and those applicable to digital video signal with standard resolution are independent of each other and have no compatibility with each other. However, assuming the case of a digital VTR in a period when plural systems are in use, it is desirable that a tape recorded by a digital VTR having high resolution (called HD VTR) be capable of being reproduced by a digital VTR having standard resolution (called SD VTR). Also, conversely, it is desirable that a tape recorded by the SD VTR be capable of being reproduced by the HD VTR. For not only a VTR but also for transmission and reception of a digital video signal, the above mentioned bidirectional compatibility is effective to make coding and decoding equipment common so as to reduce the hardware size and improve its marketability.