Video encoding method based on a wavelet decomposition

• US 20020101922A1
• Filed: 08/06/2001
• Published: 08/01/2002
• Est. Priority Date: 08/08/2000
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Pesquet-Popescu, Beatrice
• Granted Patent: US 6,782,051 B2
• Time in Patent Office: Days
• US Class Current: 375/240.1
• CPC Class Codes: H04N 19/13 Adaptive entropy coding, e.g. adaptive variable length coding [AVLC] or context adaptive binary arithmetic coding [CABAC]
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/615 using motion compensated temporal filtering [MCTF]
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/635 characterised by filter definition or implementation details

Abstract

The invention relates to a method for encoding a video sequence subdivided into groups of frames. This method comprises an on-line procedure in which a three-dimensional wavelet decomposition is performed involving a biorthogonal filter bank in a lifting scheme using optimal weighting constants. These constants are determined thanks to an additional off-line procedure in which a similar decomposition is performed but without any weighting constants.

Claims

1. An encoding method applied to a video sequence subdivided into groups of frames (GOFs) and based on an on-line procedure that comprises the steps of:

an initialization step, provided for defining for the encoding process its input parameters;

a motion estimation/compensation step, provided for performing a motion estimation and compensation between pairs of successive frames;

a spatio-temporal decomposition step, provided for carrying out a three-dimensional (3D) wavelet decomposition using a biorthogonal filter bank in a so-called lifting scheme itself using weighting constants defined in the initialization step;

an encoding step, provided for encoding the transform coefficients thus obtained,

said method being characterized in that it also comprises an off-line procedure that consists of off-line computations including the sub-steps of;

defining for this off-line procedure the same type of input parameters, with the exception of the weighting constants;

carrying out a random GOF generation sub-step, the generated GOF containing a white, Gaussian noise of mean and standard deviation adapted to the representation of the original sequence;

implementing a 3D wavelet decomposition based on said lifting scheme and using the same filter bank without any weighting constants;

computing the standard deviations of the spatio-temporal sub-bands resulting from said 3D decomposition;

dividing said standard deviations by the standard deviation of the noise, optimal weighting constants being available at the output of said division sub-step and sent towards said filter bank in order to allow to weight the output of the spatio-temporal sub-bands.

2. An encoding method according to claim 1, in which said encoding method is the so-called SPIHT algorithm.

3. An encoding method according to anyone of claims 1 and 2, in which, for an original video sequence represented on 8 bits with values from 0 to 255, a mean of 128 and a standard deviation of 32 are used for the luminance component and a mean of 128 and a standard deviation of 20 are used for the chrominance components.