Resampling and picture resizing operations for multi-resolution video coding and decoding

摘要

Techniques and tools for high accuracy position calculation for picture resizing in applications such as spatially-scalable video coding and decoding are described. In one aspect, resampling of a video picture is performed according to a resampling scale factor. The resampling comprises computation of a sample value at a position i,j in a resampled array. The computation includes computing a derived horizontal or vertical sub-sample position x or y in a manner that involves approximating a value in part by multiplying a 2n value by an inverse (approximate or exact) of the upsampling scale factor. The approximating can be a rounding or some other kind of approximating, such as a ceiling or floor function that approximates to a nearby integer. The sample value is interpolated using a filter.

主权项

1. A computer system comprising a processor and memory, wherein the computer system is adapted to perform a method comprising:
buffering a video picture; and performing upsampling of the video picture according to a horizontal upsampling scale factor and a vertical upsampling scale factor, wherein the upsampling comprises computation of an interpolated sample value at horizontal position i and vertical position j in an upsampled array, and wherein the computation comprises:
computing a derived horizontal sub-sample position x in a manner that is mathematically equivalent in result to the formula x=(i*C+D)>>S, wherein C is derived by approximating a value equivalent to 2S+F multiplied by an inverse of the horizontal upsampling scale factor, and wherein F, C, D, and S are integer values;computing a derived vertical sub-sample position y in a manner that is mathematically equivalent in result to the formula y=(j*C′+D′)>>S, wherein C′ is derived by approximating a value equivalent to 2S+F multiplied by an inverse of the vertical up sampling scale factor, and wherein D′ is an integer value; andinterpolating a sample value at the derived sub-sample position x, y.