Patent application number | Description | Published |
20090076826 | Blind Watermarking of Audio Signals by Using Phase Modifications - Watermarking of audio signals intends to manipulate the audio signal in a way that the changes in the audio content cannot be recognised by the human auditory system. In order to reduce the audibility of the watermark and to improve the robustness of the watermarking the invention uses phase modification of the audio signal. In the frequency domain, the phase of the audio signal is manipulated by the phase of a reference phase sequence, followed by transform into time domain. Because a change of the audio signal phase over the whole frequency range can be audible, the phase manipulation is carried out with a maximum amount only within one or more small frequency ranges which are located in the higher frequencies and/or in noisy audio signal sections, according to psycho-acoustic principles. Preferably, the allowable amplitude of the phase changes in the remaining frequency ranges is controlled according to psycho-acoustic principles. The watermark is decoded from the watermarked audio signal by correlating it with corresponding inversely transformed candidate reference phase sequences. | 03-19-2009 |
20090187765 | Method and apparatus for determining whether or not a reference pattern is present in a received and possibly watermarked signal - Many watermarking systems make use of correlation for calculating a detection metric, which means that several reference patterns are generated at encoder side and one or more of them are embedded inside the content signal, dependent on the message to be embedded. To decode the embedded message, it is necessary to discover which reference pattern was embedded at encoder side. This is determined by correlating the known reference patterns with the content signal. A watermark detector decides, depending on the size of the correlation result values, whether or not a given pseudo-random sequence was embedded. However, this does not provide correct decisions if watermarked audio is emitted by a loudspeaker and then captured with a microphone. According to the invention, it is taken advantage of the received signal echoes instead of treating them as noise. The watermark detection result is improved by integrating the correlation values resulting from echoes into the main correlation peak, thereby using correlation result amplitude values located within a predetermined neighborhood of a correlation result peak amplitude value and exceeding a predetermined threshold. | 07-23-2009 |
20090193255 | Method and apparatus for determining and using the sampling frequency for decoding watermark information embedded in a received signal sampled with an original sampling frequency at encoder side - Many watermarking systems make use of correlation for calculating a detection metric, which means that reference patterns are generated at encoder side and are embedded inside the audio or video signal, dependent on the message to be embedded. The same reference patterns are generated at decoder side. The embedded message is decoded by correlating the reference patterns with the watermarked signal. The watermark detector decides, depending on the size of the correlation result values, whether or not a given reference pattern was embedded. However, decoding watermarked audio or video signals is difficult if the link between the watermark encoder and the watermark decoder is not a digital one, for example an acoustic path. According to the invention, a re-sampler control unit controls the sampling frequency of a re-sampler, in connection with a watermark decoder that outputs, in addition to the watermark information bits, a corresponding confidence value that is derived from the correlation result and that is used for synchronizing the re-sampler sampling frequency with the original sampling frequency of the watermarked signal. The synchronization processing includes a search mode and a synchronized mode. | 07-30-2009 |
20090268937 | Decoding Watermark Information Items of a Watermarked Audio or Video Signal Using Correlation - Watermark information consists of several data symbols which are embedded continuously in an audio or a video signal using modulation with a pseudo-random sequence if spread spectrum technology is used. At decoder site the watermark information is regained using correlation of the received signal with a candidate pseudo-random sequence. Such correlation can be performed by one-dimensional real-symmetric fast Fourier transform of the two input signal vectors, which each consist of a section of N values of the input signal, to which section N-1 zeroes are attached, by multiplying one of the transformed vectors by the conjugated version of the other transformed vector, followed by inverse RFFT transform of that frequency domain product vector. However, if the level of a spread-spectrum watermark is too low or if too much noise had been added during the transmission of the audio or video signals, the correlation does not show a clear peak, which means that the watermark information bits cannot be recovered. According to the invention, the correlation result is improved by setting to zero in the frequency domain frequency bins of the vector which do not have a positive impact on the correlation peak at location zero, i.e. which frequency bins do not contribute to that peak. Thereby the noise level in the correlation or matched filter output is reduced and the watermark information items can be recovered or decoded correctly from the received watermarked audio or video signal. | 10-29-2009 |
20100021003 | Method and apparatus for encoding /decoding symbols carrying payload data for watermarking of an audio of video signal - Watermark information (denoted WM) consists of several symbols which are embedded continuously by reference sequence modulation in an audio or a video signal. At decoder site the WM is regained using correlation of the received signal with a corresponding reference sequence. The symbols form watermark data frames. The invention uses for the bit values ‘zero’ and ‘one’ in each payload symbol and for each payload symbol in a watermark data frame different reference sequences, without using synchronisation symbols. A logarithmic search is performed in the WM decoder to reduce the numbers of correlations to be calculated. The invention makes watermarking of critical sound signals much more robust. | 01-28-2010 |
20100121608 | METHOD AND APPARATUS FOR SETTING A DETECTION THRESHOLD GIVEN A DESIRED FALSE PROBABILITY - A method and apparatus are described for determining a threshold, including selecting a desired false result probability, and selecting a threshold value from a threshold table corresponding to the desired false result probability. Also described are a method and apparatus for determining a threshold corresponding to a desired false result probability, including calculating a false result probability, calculating a difference value between the calculated false result probability and the desired false result probability, comparing the difference value to a first predetermined value and comparing the difference value to a second predetermined value if a result of the first comparing act is positive. | 05-13-2010 |
20100166120 | Method and Apparatus for Correlating Two Data Sections - Watermarking of audio signals intends to manipulate the audio signal in a way that the changes in the audio content cannot be recognised by the human auditory system. The watermark data are decoded from the received watermarked audio signal by correlation with corresponding candidate reference sequences. One or more of the sync symbols are embedded twice in the watermark data frame in the encoder. Thereafter a circular correlation is calculated instead of a standard correlation. | 07-01-2010 |
20110103444 | Method and apparatus for regaining watermark data that were embedded in an original signal by modifying sections of said original signal in relation to at least two different - Every watermarking processing needs a detection metric to decide at decoder side whether audio signal content is marked, and which symbol is embedded inside the audio signal content. The invention provides a new detection metric that achieves a reliable detection of watermarks in the presence of additional noise and echoes. This is performed by taking into account the information contained in the echoes of the received audio signal in the decision metric and comparing it with the corresponding metric obtained from decoding a non-marked audio signal, based on calculating the false positive detection rates of the reference sequences for multiple peaks. The watermark symbol corresponding to the reference sequence having the lowest false positive error is selected as the embedded one. | 05-05-2011 |
20130070960 | PROVIDING A WATERMARKED DECODED AUDIO OR VIDEO SIGNAL DERIVED FROM A WATERMARKED AUDIO OR VIDEO SIGNAL THAT WAS LOW BIT RATE ENCODED AND DECODED - Various audio signal watermarking systems are known, which are also applied to digitally encoded audio signals. However, in current audio signal watermarking systems the watermark signal and its watermark payload do not survive very low bit rate audio coding, in particular parametric coding. According to the invention, a watermarked uncompressed audio signal bit-stream is low-bit rate compressed, but the water-marking is removed and the watermark's payload only is transmitted together with the compressed audio signal bit-stream. At decoder side, the received audio signal bit stream is de-compressed and water-marked again using the transmitted watermark payload. Advantageously, it does not matter that the compressed bitstream is not watermarked because the compressed bitstream can be encrypted prior to transmission. | 03-21-2013 |
20130073065 | METHOD AND APPARATUS FOR DETECTING WHICH ONE OF SYMBOLS OF WATERMARK DATA IS EMBEDDED IN A RECEIVED SIGNAL - Watermark symbol detection requires a detection metric for deciding at decoder side which candidate symbol is embedded inside the audio or video signal content. The invention provides an improved detection metric processing that achieves a reliable detection of watermarks in the presence of additional noise and echoes, and that is adaptive to signal reception conditions and requires a decreased computational power. This is performed by taking into account the information contained in the echoes of the received audio signal in the decision metric and comparing it with the corresponding metric obtained from decoding a non-marked audio signal, based on recursive calculation of false positive detection rates of Correlations for all REFP Reference Pattern peaks in correlation result values. The watermark symbol corresponding to the reference sequence having the lowest false positive error is selected as the embedded one. | 03-21-2013 |
20130132729 | METHOD AND SYSTEM FOR PROTECTING BY WATERMARKING AGAINST NON-AUTHORISED USE ORIGINAL AUDIO OR VIDEO DATA WHICH ARE TO BE PRESENTED - For protecting by watermarking against non-authorised use, e.g. non-authorised recording or copying, original audio or video data which are to be presented in a digital cinema, a sender site generates from the original signal at least two differently pre-watermarked versions for successive blocks or frames of the signal, wherein these versions are derived by applying a repeated watermark symbol value to a version and different watermark symbol values to the different versions. The pre-watermarked signal versions are encrypted and transferred e.g. as data files to a digital cinema unit in which they are decrypted. According to the values of a desired watermark information word, corresponding frames or blocks from said decrypted and pre-watermarked versions are assembled in a successive manner, so as to provide and present a watermarked version of said original audio or video signal that carries said watermark information word. | 05-23-2013 |
20140006790 | METHOD AND APPARATUS FOR WATERMARKING AN AC-3 ENCODED BIT STREAM | 01-02-2014 |