Abstract: Disclosed is a method of embedding both a robust and a fragile watermark in an information signal which is compressed so as to include first signal samples having a first given value and further signal samples having a different value, wherein embedding the robust watermark. The method comprises the steps of: modifying signal samples in accordance with a watermark pattern if the act of modifying results in the modified signal sample assuming the first value; and wherein embedding the fragile watermark comprises the steps of: counting the number of ‘ones’ remaining (R) in the signal as a result of embedding the robust watermark; counting the number of ‘ones’ discarded (D) from the signal as a result of embedding the robust watermark; and determining a fragile payload on the basis of said remaining (R) and discarded (D) ‘ones’.

Abstract: There is described a method of determining a measure of scale factor (MSF) by detecting a watermark included in a sequence (10) of images (20). The watermark is included in several mutually changed forms in the sequence (10). In a first step, the method involves receiving the sequence (10) of images (20). In a second step, the images (2) are sorted substantially into a plurality of corresponding groups depending upon one or more relative changes applied to their included watermarks. In a third step, the method involves accumulating for each group at least a portion of one or more images thereof into corresponding buffers. In a fourth step, the method involves mutually analyzing contents of the buffers (130, 180) to determine one or more changes applied to the watermark included in the sequence (10). In a fifth step, information concerning the one or more changes is processed in relation to an expected scale factor to determine said measure of scale factor (MSF).

Abstract: There is provided a method of scale factor retrieval in a system (10) for processing image or video programme content. The method includes steps of: (a) receiving the programme content including watermark information embedded therein; (b) subjecting the programme content to spatial correlation processes to determine a plurality of correlation peaks for one or more image or video frame axes and deriving therefrom a plurality of scale factor candidates; and (c) analysing one or more combinations of scale factor candidates to determine a combination at which at least one of correlation is improved and watermark retrieval accuracy is enhanced and thereby determining a best group of scale factor candidates. The method is capable of providing for enhanced scale factor determination and hence improved watermark retrieval.

Abstract: Watermark detectors have a buffer in which a number of image tiles are folded and accumulated prior to computing the correlation between buffer contents and the watermark pattern being looked for. The intention of the folding and accumulation process is to average out the video content while accumulating the embedded watermark energy. This no longer appears to hold for strongly compressed video, such as DIVX, which exhibits a lot of artificial noise and undesired similarity (block patterns). As a result thereof, correlation peaks are often below the threshold. In a similar manner, the compression affects scale detection. According to this invention, only frames (or parts thereof) that are not so heavily compressed and therefore have a high probability of carrying enough watermark energy are folded and accumulated. To this end, a quality metric is calculated, the quality metric being indicative of the degree of compression of the data.

Abstract: Watermark-detection in the graphics card of a personal computer, for the purpose of copy-protection, has recently started to draw a lot of attention in standardization. Detection in the graphics card has problems completely different from the formerly considered detection in the DVD-drive, having to do with high data-rates, large scale-ranges and presence of multiple video-streams in the display area. This invention proposes conversion (32) of the computer's RGB output into a luminance signal (Y) prior to watermark detection by a conventional watermark detector (31) being arranged to detect the watermark in a such a luminance signal. The resolution of the monitor image to be inspected is preferably converted (33) to the conventional TV resolution of the (MPEG2-compressed) contents being played back on the computer's DVD drive. In graphic cards providing multiple outputs (VGA, TV, DVI), the same watermark detector may be time-sequentiall connected (34) to each of the outputs.

Abstract: Watermark-detection in the graphics card of a personal computer, for the purpose of copy-protection, has recently started to draw a lot of attention in standardization. Detection in the graphics card has problems completely different from the formerly considered detection in the DVD-drive, having to do with high data-rates, large scale-ranges and presence of multiple video-streams in the display area This invention proposes examining (36) the video signal being generated by the computer system to locate image areas in which the video signal changes from frame to frame, and defining (37) a bounding box around said image areas and considering an area of interest this found as being a window in which an application is running. After approriate scale conversion (32), conventional watermark detection (31) is subsequently applied to said window. This prevents hackers from rendering illegal contents in one window while playing back a compliant disk in the DVD drive (10).

Abstract: Method and arrangement for water(re)marking a compressed video signal by modifying selected DCT coefficients. To avoid that the bitrate is thereby reduced too much, selected variable-length codewords are represented by escape codes. In order to avoid that ESC codes increase the bitrate too much (an ESC code is 7-21 bits longer than the corresponding VLC word), the bitrate is controlled in units of small data chunks. While a VLC is processed, a table is filled with candidate ESC codes. The bitrate controller tries to make the difference between original and processed data chunks zero by re-encoding one VLC into an appropriate ESC code.

Abstract: A method and apparatus (200) for embedding a watermark in an information signal bit-stream are described. The method comprises receiving a portion of an information signal bit-stream (MPEG2). A first copy of the received portion is stored in a first buffer (220). A second copy of the received portion is watermarked, and the resulting watermarked signal stored in a second buffer (240). At predetermined intervals, a check is performed to determine if the bit-rate of the received portion has been changed by being watermarked. If the check determines the bit-rate has changed, the first copy of the received portion from the first buffer is output. Otherwise the watermarked signal from the second buffer is output.

Abstract: Methods and apparatus for embedding a watermark in an information signal (MPin) are described. The watermark embedding process is controlled by at least one embedding parameter. The value of the embedding parameter is dependent upon the bit-rate of the information signal (MPin).

Abstract: Advanced watermark embedders use psycho visual/acoustic models to minimize perception of the embedded watermark in media contents. However, it is expensive to implement such advanced watermark embedders in consumer appliances (3) such as DVD recorders. In accordance with the invention, embedding strength parameters (JND) are calculated (13) off-line at a remote location (1) and transmitted along with the media contents to the consumer appliance (3). A relatively simple embedder (33) uses the received parameters to control the strength of the watermark (36) to be embedded. The parameters may be accommodated in the transmitted signal as payload of a fragile watermark or as user data in an encrypted MPEG stream.

Abstract: A method and arrangement are disclosed for embedding a watermark (W) in a media signal (MP) comprising signal samples (x(n)) being encoded as variable-length code words (VLC). The variable-length coded DCT coefficients of an MPEG2 video signal constitute such a media signal. The watermark is embedded by inverting the signs of the AC coefficients as far as such an inversion indeed causes the coefficients to be increased or decreased as prescribed (s(n)) by the watermark to be embedded. The invention is simple to implement, does not require re-encoding of the signal and does not affect the bit rate of the bit stream.

Abstract: A method for post-processing a bit stream of compressed multimedia data having been compressed by a process comprising independent compression of non-overlapping blocks of pixels covering the original multimedia data, wherein a bit rate is reduced by randomly discarding some Variable Length Codes (VLCs). The discarded VLCs are merged with subsequent VLCs to reduce bit rate.