US 7,548,583 B2 · Generation and use of masks in MPEG video encoding to indicate non-zero entries in transformed macroblocks

Abstract

During Motion Picture Experts Group (MPEG) video encoding a two-dimensional discrete cosine transform (DCT) is performed on data representing an original image. The resulting coefficients are then quantized, which typically results in many zero coefficients. Because of the nature of most video data, most higher-order coefficients are typically zero and the lower-order coefficients (i.e., those grouped towards the upper left of the matrix) are more likely to be non-zero. To reduce the lengths of runs among the lower-order coefficients, the coefficients can be encoded in a zig-zag pattern. In one embodiment, the zig-zag pattern is maintained and one or more masks are generated based on the output of the quantization phase. The one or more masks are used to identify the coefficients within the matrix that are non-zero. This reduces the number of accesses to memory required to encode the non-zero coefficients and runs of zero coefficients.

Claims30

Dependent claims

A method comprising:

transforming a set of n coefficients representing video data from a zig-zag order to a second order, n is an integer greater than 1;
generating an n-bit mask indicating whether the individual coefficients in the second order are non-zero;
determining using the mask, a number of leading zero coefficients for the non-zero coefficients;
storing the mask as one or more vectors, wherein the stored vectors are factored so that the sum of the mask can be determined using only shift and bitwise OR operations;
retrieving the non-zero coefficients;
encoding, by an encoder, the set of coefficients based on the number of leading zero coefficients determined from the mask and corresponding non-zero entries;
and
transmitting the encoded set of coefficients in an encoded video bitstream.

5 more elements

A machine-accessible medium stored computer executable instructions that, when executed, cause one or more processors to:

transform a set of n coefficients representing video data from a zig-zag order to a second order;
generate an n-bit mask indicating whether the individual coefficients in the second order are non-zero, n is an integer greater than 1;
determine using the mask, a number of leading zero coefficients for the non-zero coefficients;
store the mask as one or more vectors, wherein the stored vectors are factored so that the sum of the mask can be determined using only shift and bitwise OR operations;
retrieve the non-zero coefficients;
encode the set of coefficients based on the number of leading zero coefficients determined from the mask and corresponding non-zero entries;
and
transmit the encoded set of coefficients in an encoded video bitstream.

5 more elements

Dependencies are inferred from the claim text.

Generation and use of masks in MPEG video encoding to indicate non-zero entries in transformed macroblocks

Life of this patent

Generation and use of masks in MPEG video encoding to indicate non-zero entries in transformed macroblocks

Life of this patent

Abstract

Claims30