Chroma-key for efficient and low complexity shape representation of coded arbitrary video objects
US6459732B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jan 9, 2001 |
| Grant date | Oct 1, 2002 |
| Priority date | — |
| Expiry date | Jan 9, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N19/21
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A technique for implicitly encoding shape information by using a chroma-key color. A bounding box is created enclosing the video object. The bounding box is extended to be of size of next integer multiple of macroblock size and divided into a plurality of macroblocks. For each boundary macroblock, each pixel outside the object is replaced with the chroma-key color to implicitly encode shape information. Pixel data for boundary macroblocks and macroblocks inside the object are DCT transformed, scaled and motion compensated. A finer quantizer (smaller quantizer) is used for boundary macroblocks to improve image quality. A first_shape_code can be used to identify each macroblock as either 1) inside the object; 2) outside the object; or 3) on the object boundary. To improve data compression and achieve low complexity shape extraction with DCT and motion compensation, a first_shape_code is sent for all macroblocks, and only macroblocks that are inside the object or on the object boundary are coded. The decoding system decodes the first_shape_code and, if necessary, the DCT and motion compensation information. The motion compensated luminance and chrominance pixel values of a reconstruct…
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