DOUBLING THE NUMBER OF RASTER LINES IN TELEVISION RECEIVERS AT THE FRAME RATE

摘要

This invention is a circuit for doubling the number of raster lines in television receivers without the need for change in the transmission standards. The concept relates to improved definition television (IDTV) or enhanced definition television (EDTV). With this invention the number of lines and the resolution per line can be doubled as many times as technology permits. The circuit is based on the use of two read-write memory arrays or memory buffers and an interpolation circuit. One memory array is used to store one image, while data is being read from the other memory array. The image being read from one of the arrays is interpolated through an interpolation circuit. The role of the two memory arrays changes with every incoming image, the memory array that was in the read mode is switched to the write mode and vice-versa. The interpolation is carried-out through pixel replication in two-dimensions followed by a square symmetrical two-dimensional low-pass filter, which provides interpolation based on the Sampling Theorem. This could also be followed by a two-dimensional (2-D) circularlysymmetrical high-pass filter for image enhancement. A description of a circuit realizing a 2-D infinite impulse response filter and the filter coefficients for a square symmetrical low-pass filter having near linear phase is provided. Circuits for addressing the two memory arrays are described. The incoming image is assumed to be formed of two interlaced frames. Circuit designs are provided for displaying video images through either progressive or interlaced scanning. Interpolation could also be carried-out through a onedimensional (1-D) filter, or through the Discrete Cosine transform. These other possible variations are described in the preferred embodiment.