Proc. SPIE. 5306, Security, Steganography, and Watermarking of Multimedia Contents VI
KEYWORDS: Internet, Transparency, Detection and tracking algorithms, Digital watermarking, Computer programming, Detector arrays, Error control coding, Signal detection, Information security, Computer security
Since digital music is often stored in a compressed file, it is desirable that an audio watermarking method in a content management system handles compressed files. Using an audio watermarking method that directly manipulates compressed files makes it unnecessary to decompress the files before embedding or detection, so more files can be processed per unit time. However, it is difficult to detect a watermark in a compressed file that has been compressed after the file was watermarked.
This paper proposes an MPEG Advanced Audio Coding (AAC) bitstream watermarking method using a two-dimensional pseudo-random array. Detection is done by correlating the absolute values of the recovered MDCT coefficients and the pseudo-random array. Since the embedding algorithm uses the same pseudo-random values for two adjacent overlapping frames and the detection algorithm selects the better frame in the two by comparing detected watermark strengths, it is possible to detect a watermark from a compressed file that was compressed after the watermark was embedded in the original uncompressed file. Though the watermark is not detected as clearly in this case, the watermark can still be detected even when the watermark was embedded in a compressed file and the file was then decompressed, trimmed, and compressed again.
Proc. SPIE. 5020, Security and Watermarking of Multimedia Contents V
KEYWORDS: Signal to noise ratio, Transparency, Detection and tracking algorithms, Calibration, Computing systems, Interference (communication), Digital watermarking, Acoustics, Error control coding, Signal detection
Audio watermarking has been used mainly for digitally stored
content. Using real-time watermark embedding, its coverage can be
extended to live broadcasts and live performances. In general, a
conventional embedding algorithm receives a host signal (HS) and
outputs the summation of the HS and a watermark signal
(WS). However, when applied to real-time embedding, there are two
problems: (1) delay of the HS, and (2) possible interruption of
the broadcast. To solve these problems, we propose a watermark
generation algorithm that outputs only a WS, and a system
composition method in which a mixer outside the computer mixes the WS
generated by the algorithm and the HS. In addition, we propose a new
composition method "sonic watermarking." In this composition method, the sound of the HS and the sound of the WS are played separately by two speakers, and the sounds are mixed in the air. Using this composition method, it would be possible to generate a watermarking sound in a concerto hall so that the watermark could be detected from content recorded by audience members who have recording devices at their seats. We report on the results of experiments and discuss the merits and flaws of various real-time watermarking composition methods.
An application of watermarking for automatic music monitoring of radio broadcasts is discussed. By embedding information into the music as a watermark before broadcasting it, it is possible to keep track of what music has been on the air at what time, and for how long. However, to effectively implement this application, the handling of content transitions is important, because the detection reliability deteriorates at the content boundaries. In this paper, a method of detecting content boundaries using overlapping detection windows is described. The most probable pattern of content transition is selected under the condition that detection results from multiple windows are available. The derived rules are represented using a finite state model, which is useful for detection in real time. Experimental results on FM radio broadcasts are also presented.
Proc. SPIE. 4314, Security and Watermarking of Multimedia Contents III
KEYWORDS: Detection and tracking algorithms, Sensors, Signal attenuation, Reliability, Distortion, Digital watermarking, Reconstruction algorithms, Signal detection, Time-frequency analysis, Algorithms
In this paper, we describe an audio watermarking algorithm that can embed a multiple-bit message which is robust against wow-and-flutter, cropping, noise-addition, pitch-shift, and audio compressions such as MP3. The algorithm calculates and manipulates the magnitudes of segmented areas in the time-frequency plane of the content using short-term DFTs. The detection algorithm correlates the magnitudes with a pseudo-random array that maps to a two-dimensional area in the time-frequency plane. The two-dimensional array makes the watermark robust because, even when some portions of the content are heavily degraded, other portions of the content can match the pseudo-random array and contribute to watermark detection. Another key idea is manipulation of magnitudes. Because magnitudes are less influenced than phases by fluctuations of the analysis windows caused by random cropping, the watermark resists degradation. When signal transformation causes pitch fluctuations in the content, the frequencies of the pseudo-random array embedded in the content shift, and that causes a decrease in the volume of the watermark signal that still correctly overlaps with the corresponding pseudo-random array. To keep the overlapping area wide enough for successful watermark detection, the widths of the frequency subbands used for the detection segments should increase logarithmically as frequency increases. We theoretically and experimentally analyze the robustness of proposed algorithm against a variety of signal degradations.