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Spatio-temporal noise filter for video encoders. Disclosure Number: IPCOM000007748D
Publication Date: 2002-Apr-18
Document File: 1 page(s) / 58K

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Spatio-temporal noise filter for video encoders

Purpose: To reduce noise in a video sequence in order to improve video quality and

decrease bit rate.

General description: The video noise filter considered in this work is an adaptive

averaging spatio-temporal IIR filter proposed by L. Camiciotti and F. Bruls [1]. This noise

filter uses two past filtered frames to filter the current frame, thus accomplishing spatiotemporal

noise suppression. Typical video encoder designs operate on macro-block (MB) data

[2]. This necessitates a MB-base noise filtering.

MB-based noise filter: Fig. 1 depicts the adaptive averaging spatio-temporal filtering

operation to suppress noise [1]. The noise filtering of a pixel (see Fig. 2) depends on the four

neighbouring pixels in the current frame and the corresponding pixels in the past two filtered

frames. In order to support MB based noise filtering, we handle the boundary pixels in a MB

differently (see Fig. 3). This introduces high frequency artifacts at MB boundaries. These high

frequency artifacts are removed by the encoder's quantizer (a low-pass filter) thereby

providing similar SNR compared to a normal noise filter implementation. Therefore, the

desired objective of MB-based noise filtering is achieved without degradation in SNR.

References: [1] L. Camiciotti and F. Bruls, Adaptive filtering, WO 01/97509-A1

[2] Albert van der Werf et al., I.McIC: a single-chip MPEG2 video encoder for

storage, IEEE J. of Solid-State Circuits, vol. 32, no. 11,...