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AssigneeKoninklijke Philips Electronics N.V.
InventorsIHOR OLEHOVYCH KIRENKO, RENATUS JOSEPHUS VAN DER VLEUTEN
Estimating the term…
A hither before unknown cause of image artefacts has been identified. Encoders such as MPEG encoders may use two picture structures: Field pictures and frame pictures. For a frame picture both frame and field-based DCT (and other types) of coding may be used. The decision whether to use frame or field based coding is not always made correctly. In the decoded image this leads to an image artefact visible as stripped blocks. The invention reduces, in one aspect of the invention, these artefacts by analyzing the block content on the presence of such artefacts and if the analysis proof the existence of such artefacts applying a vertical low pass filter to the data in the block. In another aspect of the invention encoding parameters are checked for combination of encoding parameters for which the artefact may occur and such blocks are indicated. The invention may be embodied in a method as well as in a device such as a receiver, encoder, decoder, display device etc.
A method of processing a compressed image data stream in which method compression artefacts are reduced wherein for a decoded image block or for a group of decoded image blocks at least one difference value (yes count, Gv) is determined (1) from differences in pixel data in a vertical direction between adjacent lines and the difference value is compared to a threshold (k*no count, k*Gh) wherein in case the difference value meets the threshold, low pass filtering (2) in vertical direction is applied to the decoded image block or blocks.
A reducer for reducing image artefacts in wherein the reducer comprises a determinator for determining for a or for a group of decoded image blocks at least one difference value (Yes count, Gv) from differences in pixel data in a vertical direction between adjacent lines and a comparator (C) for comparing the at least one difference value is compared to a threshold (k*no count, k*Gh) and a low pass filter to apply low pass filtering (2) in vertical direction to the decoded image block or blocks in case the difference value meets the threshold.
A method for analyzing encoding parameters of an encoded image data stream wherein blocks or macroblocks in a frame picture for which the encoder may have performed a frame or a field encoding are indicated.
Analyzer (AN) for analyzing encoding parameters of an encoded image data stream the analyzer comprising a means for indicating blocks or macroblocks in a frame picture for which the encoder may have performed a frame or a field encoding.
Signal comprising an image data stream which signal comprises indicators I indicating for blocks or groups of blocks the possibility a wrong frame/field encoding.
Signal for an image data stream which signal comprises indicators I indicating for blocks or groups of blocks the possibility a wrong frame/field encoding.
Dependencies are inferred from the claim text.