Method and apparatus for coding segmented regions which may be transparent in video sequences for content-based scalability

摘要

A method and apparatus for generating region frames from video frames are disclosed which employs an industry standard encoder to lessen the negative impact on the quality of the transmitted video sequence while consuming fewer bits. The invention utilizes image segmentation and color replacement techniques to create the region frames. Each region frame includes a subject region, zero or more previously segmented regions and zero or more non-subject regions. The subject region is defined by the pixels of the original video frame. The previously segmented regions and non-subject regions are assigned replacement pixels P.sub.n,y and C.sub.n, respectively. The replacement pixel C.sub.n is chosen to indicate a color that is not likely to be confused with any color in the subject region R.sub.n. The replacement pixels P.sub.n,y are chosen such that the compression ratio of the region frame data is maximized. Using the region frames, content based scalability can be provided without the need for special encoders and/or channels having a wider bandwidth. The decoder may comprise color or chroma keying apparatus or circuitry keying on the replacement color C. sub.n. Instead of keying on a single value, two thresholds may be assigned to define a boundary condition or a subject semi-transparent region. The decoder is forwarded data of the two thresholds and a flag is sent to indicate the dial boundary or semi- transparent region coding. A blending process blends the foreground and background of the semi- transparent object.