Frequency domain filtering for down conversion of a DCT encoded picture
US6175592A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 12, 1997 |
| Grant date | Jan 16, 2001 |
| Priority date | — |
| Expiry date | Mar 12, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N19/90
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A discrete cosine transform domain (DCT) filter for lowpass filtering a high resolution encoded video image represented as frequency-domain coefficient values, such as macroblocks, before decimation of the video image in the spatial domain. The DCT filter masks or weights the DCT coefficients of the video image macroblocks before processing by an inverse DCT. The filter may be implemented as a block mirror filter in the frequency domain, and the filter values may be combined with the IDCT coefficient values. Original motion vectors of the high resolution encoded video image are translated because low resolution reference images used by the decoder are not equivalent to the original high resolution images. Therefore, motion vectors are scaled to retrieve low resolution prediction blocks which are up-sampled to generate the original pixel and half-pixel values in the spatial domain. The up-sampled prediction block is added to the DCT filtered inverse-DCT transformed pixel values if the current macroblock is part of a non-intraframe encoded image. After motion compensation processing of the original macroblock, the reconstructed macroblock in the lower resolution is decimated accordin…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.