Coding and noise filtering an image sequence

• US 20030053709A1
• Filed: 10/29/2002
• Published: 03/20/2003
• Est. Priority Date: 01/15/1999
• 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: Olivieri, Stefano
• Granted Patent: US 6,993,195 B2
• Time in Patent Office: Days
• US Class Current: 382/261
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/147 according to rate distortion criteria rate-distortion as a criterion for motion estimation H04N19/567
• CPC Class Codes: H04N 19/149 by estimating the code amount by means of a model, e.g. mathematical model or statistical model
• CPC Class Codes: H04N 19/172 the region being a picture, frame or field
• CPC Class Codes: H04N 19/19 using optimisation based on Lagrange multipliers
• CPC Class Codes: H04N 19/51 Motion estimation or motion compensation
• CPC Class Codes: H04N 19/60 using transform coding
• CPC Class Codes: H04N 19/61 in combination with predictive coding
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/82 involving filtering within a prediction loop

Abstract

The invention provides a method of and a device for coding (10*) an image sequence (g(i,j,k)). The device (10*) has a noise filter (12) for noise filtering (12) the image sequence (g(i,j,k)), and means (12) for regarding the noise filtering (12) as a rate-distortion optimization problem in order to adapt the response of the noise filter (12). In particular, a filter parameter set (C) is determined to adapt the response of the filter (12) in that the image sequence (g(i,j,k)) is encoded using an optimal bit-budget, which is the bit-budget used for compressing a noise-free image sequence, and the distortion for the given bit-budget is minimized.

A solution of the rate-distortion problem is proposed that calculates (12) the filter parameter set (C) by a Lagrange multiplier method. Separate minimization is used to determine each parameter of the parameter set (C) independently. In a practical embodiment, a spatial adaptive weighted averaging (SAWA) filtering (23) is used to estimate the bit budget (R^f*) and to pre-filter the image sequence (g(i,j,k)).

Claims

1. A method of coding (10,10*) an image sequence (g(i,j,k)), the method comprising the steps of:

noise filtering (12) the image sequence (g(i,j,k)); and

adapting (12*) said noise filtering (12) in dependence on a rate-distortion optimization of said coding (10,10*).

2. A method as claimed in claim 1, wherein the adapting step (12*) comprises the steps of:

calculating (12*) a filter parameter set (C) of said noise filtering (12) by a Lagrange multiplier method; and

estimating (12*) an optimal Lagrange multiplier by determining a maximum of a second derivative of a rate used in the rate-distortion optimization.

3. A method as claimed in claim 1, wherein the adapting step comprises the steps of:

spatial filtering (23) the image sequence; and

taking (17) a number of bits that is used to encode the spatially filtered image sequence as a rate used in the rate-distortion optimization.

4. A device (10,10*) for coding an image sequence (g(i,j,k)), the device comprising:

means (12) for noise filtering the image sequence (g(i,j,k)); and

means (12*) for adapting a response of said means for noise filtering (12) in dependence on a rate-distortion optimization of said coding (10,10*).

5. A camera system comprising a camera (100) and a device (200) as claimed in claim 4.